Search

Mucor rot caused by Mucor piriformis is an emerging postharvest disease of mandarin fruit in California. Natamycin is a newly registered biofungicide for postharvest use on citrus and some other fruits. In the study, baseline sensitivity to natamycin in 50 isolates of M. piriformis was determined in vitro. The mean EC 50 (effective concentration to inhibit sporangiospore germination by 50%) and MIC (minimum inhibitory concentration to inhibit mycelial growth by 100%) values were 0.59 μg/ml and less than 1.0 μg/ml, respectively. Natamycin at the label rate of 920 μg/ml alone or in combination with 3% potassium sorbate (PS) or 3% sodium carbonate (SC) applied at 20 or 50°C was evaluated for control of Mucor rot on inoculated 'Tango' mandarin fruit. Natamycin alone reduced Mucor rot incidence on stored mandarin fruit from 100% among nontreated control fruit to approximately 30%, a reduction of more than 70% compared to the nontreated control, while 3% PS and 3% SC had no to little control. When applied at 50°C, natamycin and 3% PS reduced Mucor rot incidence by 65.0 and 31.2%, respectively; while natamycin in combination with 3% PS reduced disease incidence by 92.5% compared to the nontreated control after 2 weeks of storage at 5°C. This combined treatment remained effective even when the application of the treatment was delayed for 6 and 12 h after inoculation. However, the effectiveness of the treatments declined when storage was extended to 3 or 4 weeks. Natamycin can be an effective tool to control Mucor rot on mandarin fruit, and minimizing the period of extended storage could help maintain the control efficacy of natamycin., Competing Interests: The author(s) declare no conflict of interest.

Alternaria rot, caused by Alternaria alternata and A. arborescens , is one of the common postharvest diseases affecting mandarin fruit in California. Fungicide resistance profilings of A. alternata and A. arborescens to quinone outside inhibitors (QoIs), fludioxonil, pyrimethanil, imazalil, and propiconazole were examined in this study. Of the 100 isolates of A. alternata and A. arborescens , 40 were identified as resistant to QoI fungicides according to a PCR-restriction fragment length polymorphism based on a cytochrome b partial gene. Effective concentrations of fludioxonil that caused a 50% reduction in fungal growth relative to the control (EC 50 ) were 0.089 ± 0.020 and 0.101 ± 0.032 µg/ml for 43 A. alternata and 19 A. arborescens isolates, respectively. EC 50 values of pyrimethanil, imazalil, and propiconazole for the 70 A. alternata isolates tested were 0.373 ± 0.161, 0.492 ± 0.133, and 1.135 ± 0.407 µg/ml, respectively. EC 50 values of pyrimethanil, imazalil, and propiconazole for 30 A. arborescens isolates were 0.428 ± 0.190, 0.327 ± 0.180, and 0.669 ± 0.452 µg/ml, respectively. Control tests on mandarin fruit inoculated with representative isolates of both species showed that fludioxonil, pyrimethanil, imazalil and propiconazole significantly reduced disease incidence and severity. Azoxystrobin significantly reduced Alternaria rot severity and incidence on mandarin fruit inoculated with sensitive isolates but not with resistant isolates, regardless of Alternaria spp. There were no significant differences in Alternaria rot control effectiveness if treatment with any of the fungicides tested was delayed after inoculation by 6 or 12 h. These results could help in the development of postharvest fungicide programs to control Alternaria rot on mandarin fruit during storage., Competing Interests: The author(s) declare no conflict of interest.

Alternaria rot caused by Alternaria alternata is one of the major postharvest diseases affecting blueberries in California. The sensitivity profiles of A . alternata from blueberry field to quinone outside inhibitors (QoIs), boscalid, fluopyram, fludioxonil, cyprodinil, and polyoxin D in California were examined in this study. EC 50 values of 51 A . alternata isolates for boscalid varied greatly among the isolates, ranging from 0.265 to >100 μg/ml. EC 50 values of 51 A . alternata isolates to fluopyram, fludioxonil, cyprodinil, and polyoxin D were 5.188 ± 7.118, 0.078 ± 0.021, 0.465 ± 0.302, and 6.238 ± 7.352 μg/ml, respectively. In total, 143 isolates were screened for resistance at 5 and 10 μg/ml for fludioxonil, cyprodinil, and fluopyram, 10 μg/ml for polyoxin D, and 10 and 50 μg/ml for boscalid. Based on the published discriminatory concentrations for phenotyping resistance, of the 143 isolates, all were considered resistant to boscalid; 32, 69, and 42 were sensitive, low resistant, and resistant to fluopyram, respectively; and all were sensitive to fludioxonil and cyprodinil. In a PCR-restriction fragment length polymorphism method for phenotyping, 60 out of the 143 isolates were classified as resistant to QoIs. Control tests on detached blueberry fruit inoculated with different Alternaria isolates showed that fludioxonil and cyprodinil significantly reduced disease incidence and severity; however, pyraclostrobin, boscalid, fluopyram, and polyoxin D significantly reduced only disease severity. The obtained results will be helpful in making decisions on fungicide programs to control A . alternata isolates with resistance or reduced sensitivities to multiple fungicides.

Alternaria rot caused by Alternaria alternata and A. arborescens is one of the major postharvest diseases on mandarin fruit in California. In this study, natamycin, a newly registered biofungicide, was evaluated for its potential as a postharvest treatment to control Alternaria rot on mandarin fruit. The baseline sensitivities of A. alternata and A. arborescens to natamycin were determined. Effective concentration inhibiting 50% of fungal growth (EC 50 ) values of natamycin for 70 A. alternata isolates ranged from 0.694 to 1.275 µg/ml (mean = 0.921 µg/ml) in a conidial germination assay and from 2.001 to 3.788 µg/ml (mean = 2.797 µg/ml) for 40 A. alternata isolates in a mycelial growth assay. EC 50 values of natamycin for 30 A. arborescens isolates ranged from 0.698 to 1.203 µg/ml (mean = 0.923 µg/ml) in a conidial germination assay and from 2.035 to 3.368 µg/ml (mean = 2.658 µg/ml) for 20 A. arborescens isolates in a mycelial growth assay. Control tests on detached mandarin fruit showed that natamycin at both low (460 µg/ml) and high (920 µg/ml) recommended rates significantly reduced disease incidence and severity on mandarin fruit inoculated with Alternaria isolates, regardless of species. High rate of natamycin significantly reduced disease incidence and severity compared with the nontreated control even when natamycin treatment was delayed for 6, 12, and 18 h after inoculation. Our results suggested that natamycin can be an effective postharvest fungicide for control of Alternaria rot on mandarin fruit.

Postharvest diseases are a limiting factor in the storage of fresh blueberries. Gray mold caused by Botrytis cinerea and Alternaria rot caused by Alternaria spp. are important postharvest diseases in blueberries grown in California. Control of these fungal pathogens is generally dependent on preharvest sprays of synthetic fungicides, but in California multiple fungicide resistance has already developed in those pathogens, leading to the failure of disease control. Therefore, alternatives to synthetic fungicides are needed for the control of postharvest diseases. Peroxyacetic acid (PAA) is a disinfectant agent that poses low risk to human health. In this study, we evaluated the effects of postharvest use of PAA at 24 µl liter -1 and 85 µl liter -1 on fruit decay caused by fungal pathogens and quality of stored blueberry fruit. PAA treatment was applied to four cultivars over three seasons using two methods, dipping or spraying. Dipping blueberries compared with spraying them with PAA and its application at 85 µl liter -1 were the most effective treatments. For example, when applied to 'Snowchaser' blueberries, this combination reduced naturally occurring decay after 4 weeks of storage at 0 to 1°C from 14.3% among water-treated controls to 2.7% in 2018, and from 25.7% among water-treated controls to 8.6% in 2020. In general, PAA did not adversely affect fruit quality or sensory quality of blueberries. Postharvest use of PAA appears to be a promising means to reduce postharvest decay of blueberries. To reliably obtain an acceptable level of disease control, the best use of PAA may be in combination with other practices rather than using it alone.

Alternaria rot caused by Alternaria species is one of the major postharvest diseases of mandarin fruit in California. The aims of this study were to identify these Alternaria species via phylogenetic analyses and morphological characteristics and test their pathogenicity on mandarin. Decayed mandarin fruits exhibiting Alternaria rot symptoms were collected from three citrus fruit packinghouses in the Central Valley of California. In total, 177 Alternaria isolates were obtained from decayed fruit and preliminarily separated into three groups representing three species ( A. alternata , A. tenuissima , and A. arborescens ) based on the colony characterization and sporulation patterns. To further identify these isolates, phylogenetic analysis was conducted based on DNA sequences of the second largest subunit of RNA polymerase II ( RPB2 ), plasma membrane ATPase ( ATPase ), and Calmodulin gene regions in combination with morphological characters. Of the 177 isolates, 124 (70.1%) were identified as A. alternata , and 53 (29.9%) were A. arborescens . The isolates initially identified as A. tenuissima based on the morphological characteristics could not be separated from those of A. alternata in phylogenetic analysis and thus considered A. alternata . Pathogenicity tests showed that both Alternaria species were pathogenic on mandarin fruit at both 5°C and 20°C. Our results indicated that two Alternaria species, A. alternata and A. arborescens , were responsible for Alternaria rot of mandarin fruit in California, with A. arborescens causing fruit rot on mandarin being reported for the first time.

Botrytis cinerea on grapes causes bunch rot at both pre- and postharvest stages, in which losses can reach up to 100%. Chemical control primarily relies on the prophylactic use of site-specific fungicides. Repeated applications of these products raise the risk of fungicide resistance development in B. cinerea populations, which can result in disease control failures. To determine the extent of resistance, B. cinerea isolates were collected from grape clusters in the northwest and southwest grape growing regions of Michigan in 2014 and 2018 ( n = 115 and 125, respectively). These isolates were phenotyped using discriminatory doses of eight fungicides to determine the levels of resistance. Fungicide resistance increased from 2014 to 2018, mostly affecting the active ingredients fenhexamid, fluopyram, and iprodione. B. cinerea isolates resistant to multiple fungicides were detected in 2014 and 2018, with a higher frequency of resistance in 2018. TaqMan real-time PCR has been developed to detect B. cinerea fungicide resistance to fenhexamid and to differentiate the erg27 F412S/I/V alleles. The TaqMan assay was tested for sensitivity, specificity, and reproducibility on purified DNA and infected grape tissue samples. Our data provide essential information to growers about the efficacy for B. cinerea control using the available botryticides. Furthermore, the developed fenhexamid markers will be transferred to diagnostic clinics to assist growers in the management of bunch rot before resistance-related control failures occur.

Gray mold caused by Botrytis cinerea is an emerging postharvest disease of mandarin fruit in California. Management of postharvest diseases of mandarins relies on postharvest fungicides; however, multiple resistance to fungicides of different modes of action is common in B. cinerea populations from mandarin, leading to their failure to control decay. Natamycin is commonly used in the food industry as an additive, and it has been registered as a biofungicide for postharvest use on citrus and some other fruits. Sensitivity to natamycin of 64 isolates of B. cinerea from decayed mandarin fruit with known resistance phenotypes to other citrus postharvest fungicides (azoxystrobin, fludioxonil, pyrimethanil, and thiabendazole) was tested. Effective concentrations of natamycin to cause a 50% reduction relative to the control for conidial germination were from 0.324 to 0.567 µg/ml (mean of 0.444 µg/ml), and those for mycelial growth were 1.021 to 2.007 µg/ml (mean of 1.578 µg/ml). Minimum inhibitory concentrations where no fungal growth was present were 0.7 to 1.0 µg/ml for conidial germination and 5.0 to 10.0 µg/ml for mycelial growth. No cross-resistance between natamycin and other citrus postharvest fungicides was detected. Decay control efficacy tests with natamycin were conducted on mandarin fruit inoculated with B. cinerea isolates exhibiting five different fungicide resistance phenotypes, and natamycin significantly reduced incidence and lesion size of gray mold on fruit, regardless of fungicide resistance phenotypes. Natamycin has the potential to be an effective tool for integration into postharvest fungicide programs to control gray mold and manage B. cinerea isolates resistant to fungicides with other modes of action.

Members of the genera Neofabraea and Phlyctema have been reported to incite canker diseases of apple trees and a postharvest decay of apple fruit referred to as "bull's-eye rot." Neofabraea kienholzii was recently identified as participating in the bull's-eye rot disease complex of apple and other pome fruit. In this study, apple twigs inoculated with N. kienholzii were shown to develop symptoms of a canker disease closely resembling perennial canker of pome fruit trees caused by N. perennans. Cankers resulting from infection by either Neofabraea spp. were more likely to be induced when twig inoculations occurred in October, and to a lesser degree in April, compared with all other inoculation dates evaluated in this study. Although N. kienholzii tended to induce cankers that were smaller in size compared with N. perennans, both pathogens shared similar seasonal trends in the initiation and expansion of tree cankers. N. perennans and N. kienholzii were recovered from inoculated twigs 6 months postinoculation regardless of when inoculations were conducted, indicating that both pathogens can survive on diseased twigs year-round. In addition, acervuli were observed more often on twigs inoculated in September and April compared with those inoculated in other months. Data from this work should help further our understanding of the epidemiology of N. kienholzii. This information also highlights the importance of proper branch pruning, canker removal, and aphid control. Such management activities should be conducted in a manner that helps minimize further spread of the pathogen.

Gray mold caused by Botrytis cinerea is an emerging postharvest disease affecting stored mandarin fruit in California. To develop effective control programs, fungicide sensitivities to four citrus postharvest fungicides were determined. One hundred B. cinerea isolates each in 2015 and 2016 were obtained from decayed fruit collected within packinghouses and tested for resistance to the fungicides. Sensitivity to azoxystrobin was examined based on the point mutation in the cyt b gene using PCR, while resistance to fludioxonil, pyrimethanil, and thiabendazole was examined on fungicide-amended media. For azoxystrobin, 83 and 98% of the isolates were resistant in 2015 and 2016, respectively. For pyrimethanil, 71 and 93% were resistant in 2015 and 2016, respectively. For thiabendazole, 63 and 68% were resistant in 2015 and 2016, respectively. No fludioxonil resistance was detected in both years. Five fungicide-resistant phenotypes were detected, and the most common phenotype was triple resistance to azoxystrobin, pyrimethanil, and thiabendazole, accounting for 59 and 65% in 2015 and 2016, respectively. Of the 200 B. cinerea isolates, 5, 23.5, and 62% were resistant to one, two, or three classes of fungicides, respectively. Inoculation tests were conducted to evaluate if the fungicides at label rates controlled various resistant phenotypes on fruit. Most fungicides failed to control gray mold on mandarin fruit inoculated with the respective fungicide resistant phenotypes. Our results suggest that alternative control methods need to be integrated into existing decay control programs to target this emerging disease on mandarin fruit.

Brown rot is a severe disease affecting stone and pome fruit. This disease was recently confirmed to be caused by the following six closely related species: Monilinia fructicola, M. laxa, M. fructigena, Monilia polystroma, M. mumecola, and M. yunnanensis. Because of differences in geographic distributions, some of these species are important quarantine pathogens in certain countries. In this study, we developed TaqMan real-time polymerase chain reaction (PCR) assays to detect and identify the six species. Primer pairs and probes were designed for Monilinia fructicola, M. fructigena, M. laxa, and Monilia polystroma based on sequence differences in the laccase-2 genes. Additionally, based on sequence differences in the elongation factor genes, primer pairs and probes were designed for Monilia mumecola and M. yunnanensis. The real-time PCR assays were able to specifically identify the target pathogens, with detection limits of 10 to 100 fg of DNA, which is equivalent to one to seven conidia. The assays were also able to detect the target pathogens in a mixed DNA sample comprising all six Monilinia spp. and related species. The real-time PCR assays accurately detected target fungi from infected apple fruit. Furthermore, the identification results were consistent with those of traditional morphological methods.

Bull's-eye rot is a major postharvest disease of apple caused by several fungi belonging to the Neofabraea and Phlyctema genera. Chemical control of these fungi is a crucial component of disease management for apples that are conventionally grown. The efficacy of several preharvest and postharvest applied fungicides were evaluated to identify effective chemistries that can control bull's-eye rot incited by Neofabraea perennans and N. kienholzii on apples. In general, the preharvest fungicide thiophanate-methyl was found to be effective at reducing disease caused by N. perennans and N. kienholzii. Two postharvest fungicides, thiabendazole and pyrimethanil, also provided disease control that was far superior to other chemical compounds evaluated in this study. The efficacy of thiabendazole and pyrimethanil was unaffected by application method (fungicide dip compared with thermofog). Despite providing satisfactory control of bull's-eye rot, integration of these three chemicals into disease management programs should proceed judiciously with consideration of their impact on the development of fungicide resistance and influence on diversity in populations of apple postharvest pathogens.

Bull's-eye rot is a postharvest disease of pome fruit in the U.S. Pacific Northwest. The disease is caused by the fungi Neofabraea kienholzii, N. malicorticis, N. perennans, and N. vagabunda. Fruit infection by these pathogens is initiated in the orchard during the fruit-growing season but remains latent at harvest. For fruit held in postharvest cold storage, bull's-eye rot symptom development is slow to progress, requiring at least 3 months before symptoms are first visible. In order to determine the timing of preharvest fruit infection in relation to bull's-eye rot development in cold storage, 'Red Delicious' and 'Fuji' apple fruit were inoculated with a conidial suspension of N. perennans or N. kienholzii at different inoculation timings throughout the fruit growing seasons of 2012 to 2014. Fruit were harvested and stored at 0°C for up to 10 months, during which time disease incidence was recorded periodically. Results from this study demonstrate that apple fruit infection by either pathogen may occur at any point during the growing season. However, infections occurring over the 8-week period immediately prior to harvest yield a higher incidence of bull's-eye rot in stored fruit compared with infections initiated earlier in the growing season.

Gray mold caused by Botrytis cinerea is a major postharvest disease of blueberry grown in the Central Valley of California and western Washington State. Sensitivities to boscalid, cyprodinil, fenhexamid, fludioxonil, and pyraclostrobin, representing five different fungicide classes, were examined for 249 (California) and 106 (Washington) B. cinerea isolates recovered from decayed blueberry fruit or flowers. In California and Washington, 7 and 17 fungicide-resistant phenotypes, respectively, were detected: 66 and 49% of the isolates were resistant to boscalid, 20 and 29% were moderately resistant to cyprodinil, 29 and 29% were resistant to fenhexamid, and 66 and 55% were resistant to pyraclostrobin. All isolates from California were sensitive to fludioxonil, whereas 70% of the isolates from Washington showed reduced sensitivity to fludioxonil. In California, 26 and 30% of the isolates were resistant to two and three classes of fungicides, respectively. In Washington, 31, 14, 16, and 9% of the isolates were resistant to two, three, four, and five classes of fungicides, respectively. Inherent risk of the development of resistance to quinone outside inhibitor (QoI) fungicides was assessed by detecting the presence of the Bcbi-143/144 intron in gene cytb. The intron was detected in 11.8 and 40% of the isolates in California and Washington, respectively, suggesting that the risk of QoI resistance is higher in California than in Washington. On detached blueberry fruit inoculated with 11 isolates exhibiting different fungicide-resistant phenotypes, most fungicides failed to control gray mold on fruit inoculated with the respective resistant phenotypes but the mixture of cyprodinil and fludioxonil was effective against all fungicide-resistant phenotypes tested. Our findings would be useful in designing and implementing fungicide resistance management spray programs for control of gray mold in blueberry.

In recent years, an emerging, undescribed postharvest disease was observed on mandarin fruit after extended storage in California. We collected decayed mandarin fruit from three citrus packinghouses in the Central Valley of California in 2015 and identified this disease as Mucor rot caused by Mucor spp. Mucor rot occurred in 11 of the 15 grower lots sampled, and the percentage of Mucor rot in the total decayed fruit varied among affected grower lots, ranging from 3.3 to 93.1% with an average of 49.2%. In total, 197 isolates of Mucor spp. were obtained from decayed mandarin fruit and identified based on internal transcribed spacer sequence and morphological characteristics. Of the 197 isolates, 182 (92.4%) were identified as Mucor piriformis, 7 (3.6%) were M. circinelloides (6 M. circinelloides f. lusitanicus and 1 M. circinelloides f. circinelloides), 4 (2%) were M. racemosus f. racemosus, 3 (1.5%) were M. hiemalis, and 1 (0.5%) was M. mucedo. All species grew at 0 and 5°C, except M. circinelloides, which did not grow at 0°C. Mycelial growth was arrested at 27°C for M. piriformis; 35°C for M. racemosus f. racemosus, M. circinelloides f. lusitanicus, M. hiemalis and M. mucedo; and 37°C for M. circinelloides f. circinelloides. Optimal mycelial growth occurred at 20°C for M. piriformis and M. mucedo, 25°C for M. racemosus f. racemosus and M. hiemalis, 27°C for M. circinelloides f. lusitanicus, and 30°C for M. circinelloides f. circinelloides. M. piriformis grew significantly faster than the other four species at 5 and 20°C, and M. mucedo was the slowest in growth among the five species. Sporangiospores of M. piriformis, M. racemosus f. racemosus, and M. hiemalis germinated at both 5 and 20°C. M. circinelloides germinated at 20°C but did not germinate at 5°C after incubation for 48 h. All five Mucor spp. caused decay on mandarin fruit inoculated with the fungi, and the lesion size caused by M. piriformis was significantly larger than that caused by other species at both 5 and 20°C. Our results indicated that Mucor rot in mandarin fruit in California is caused by Mucor spp. consisting of M. piriformis, M. circinelloides, M. racemosus f. racemosus, M. hiemalis, and M. mucedo, with M. piriformis being the dominant and most virulent species. Previously, M. racemosus was reported on citrus. This is the first report of Mucor rot in citrus caused by M. piriformis, M. circinelloides, M. hiemalis, and M. mucedo.

During surveys for postharvest diseases of apple and pear, an unknown postharvest fruit rot was observed in Washington State. The disease appeared to originate from infection of the stem and calyx tissue of the fruit or wounds on the fruit. An unknown pycnidial fungus was consistently isolated from the decayed fruit. Isolates from apple and pear were characterized and identified by molecular phylogenetic analysis and morphology. Pathogenicity of representative isolates on apple and pear fruit was tested under laboratory or field conditions. A BLAST search in GenBank showed that isolates differed from Phacidium lacerum and its synonym, Ceuthospora pinastri, by only 0 to 4 bp in sequences within part of the combined large ribosomal subunit + internal transcribed spacer + small ribosomal subunit regions. The phylogenetic analysis confirmed the taxonomic placement of the unknown fungus in the genus Phacidium, with the highest match being C. pinastri (formerly anamorphic P. lacerum) and with closely related taxa from GenBank forming congeneric clades. The fungus grew at 0 to 30°C and formed unilocular to multilocular pycnidial conidiomata on artificial media after approximately 5 to 7 days at room temperature. On potato dextrose agar incubated for a 12-h photoperiod, semi-immersed globose to subglobose pycnidial conidiomata were 250 to 1,000 μm in diameter (mean = 350), with 1 to 3 nonpapillate to slightly papillate ostioles and a buff conidial matrix. Conidia produced on phialides were 8 to 13 by 1.5 to 2.5 μm, hyaline, aseptate, cylindrical, with an abruptly tapered, typically slightly protuberant base, 2 to 3 guttules, and sometimes with a mucilaginous, flexuous, unbranched appendage which is attached to the apex of the conidium and disappears with age. Conidiogenous cells were flask shaped and 6 to 15 ×1.5 to 3 μm. Colony characteristics included felt-like aerial white mycelium, gray olivaceous at the center becoming greenish to colorless toward the margin, in concentric rings, with pycnidia forming in 5 to 7 days originating from the center of the plate. Morphological characteristics of the fungus had the greatest conformity with the description for C. pinastri. Based on molecular and morphological data, the fungus is identified as P. lacerum. 'Fuji' apple fruit and 'd'Anjou' pear fruit that were wounded, inoculated with representative isolates, and incubated at 0°C yielded the same symptoms as seen on decayed fruit collected from commercial fruit packinghouses. Stem-end rot, calyx-end rot, and wound-associated rot developed on fruit inoculated in the orchard after 3 months of cold storage. The fungus was reisolated from the diseased fruit. This is the first report of a fruit rot in apple and pear caused by P. lacerum. We propose Phacidium rot as the name of this disease.

During surveys for postharvest diseases of apple conducted in Washington State, an unknown fruit rot was observed on stored apple fruit collected from commercial fruit packinghouses. This disease was present in 66 of the 179 grower lots sampled, accounting for an average 1 to 3% of the total decayed fruit sampled. The disease appeared to originate from infection of wounds on the fruit skin. Lesions were brown and decayed tissues were spongy. A Lambertella sp. was consistently isolated from the decayed fruit. Sequences of the fungus and those of Lambertella corni-maris in GenBank differed by 0 to 4 bp across the combined small ribosomal subunit + internal transcribed spacer + large ribosomal subunit regions with a maximum identity ranging from 99 to 100%. The fungus grew at 0 to 20°C and formed apothecia on artificial media after 8 to 24 weeks. On potato dextrose agar under a 12-h photoperiod, apothecial dimensions were variable, ranging from 1 to 6 mm in diameter with stipes of 1 to 4 by 0.5 mm. Asci were 76 to 125 by 3.5 to 5.5 μm, inoperculate, eight-spored, clavate, and narrowed at the base. Ascospores were aseptate, 7 to 10 by 2.5 to 4.5 μm, uniseriate to biseriate, and orange-brown at maturity in the ascus. Colony characteristics included little or no aerial mycelium, dark-yellow to gray-black mycelium, gray-black pseudosclerotia, and yellow pigmentation in the agar. Morphological characteristics of the fungus overlapped with the description of L. corni-maris. 'Fuji' apple fruit that were wounded, inoculated with representative isolates, and incubated at 0°C yielded the same symptoms as seen in packinghouses, and the fungus was reisolated from the diseased fruit. This is the first report of a fruit rot in stored apple caused by L. corni-maris in the United States. We propose Lambertella rot as the name of this disease.

In recent years, a leaf blight disease, consisting of browned, desiccated leaves occurring mainly in the lower parts of the canopy, has been observed during wet springs on Pacific madrone (Arbutus menziesii) in western Washington and Oregon. In May 2009 and 2011, severe outbreaks occurred and symptomatic leaves from madrones growing in the region were sampled to determine the causal agent. Two symptoms, leaf necrosis or blotching along the edges and tips of the leaves, and leaf spot, were observed. Small segments of diseased tissue were cut from the leaves, surface-disinfected, rinsed, and plated on malt extract agar. Fifty percent of the leaf blotch and 30% of leaf spot samples yielded a fungus that was fast-growing (20 mm diameter in 4 days at 25°C) and produced colonies that were a pale gray with dark gray reverse and a felty texture. On potato dextrose agar (PDA), pycnidia formed and exuded conidia in peach-colored droplets after 2 weeks under room temperature and light conditions. Pycnidia were spherical and 12.5 to 39.8 μm, average 24.2 μm in diameter. Conidia were hyaline, ovoid, and 5.8 to 8.5 × 3.1 to 4.7 μm (average 7.0 × 3.7 μm). The fungus was identified as Phacidiopycnis washingtonensis based on its morphology (1). To confirm the identity, the internal transcribed spacer (ITS) region of the rDNA was amplified with ITS1/ITS4 primers (2) and sequenced (GenBank Accession Nos. JQ743784 to 86). BLAST analysis showed 100% nucleotide identity with those of P. washingtonensis in GenBank (AY608648). The fungus was also isolated from lesions on green shoots and the petiole and leaf blade of dead attached leaves. To test pathogenicity, 3-year-old Pacific madrone seedlings (three for each isolate) were inoculated with five isolates of the fungus and maintained in the greenhouse (25°C); the experiment was conducted twice. Five leaves from each tree were cold injured (-50°C) at a marked 5 × 5 mm 2 area with a commercial aerosol tissue freezing product prior to inoculation and five leaves were not cold injured. A 5-mm-diameter mycelial plug cut from the margin of 6-day-old PDA culture was applied to the marked areas on the upper leaf surface. The inoculated area was covered with moist cheese cloth and wrapped with Parafilm. Leaves treated with blank PDA plugs served as control. Leaves were enclosed in plastic bags to maintain moisture for the first 15 h post inoculation and cheese cloths were removed after 15 days. All cold-injured inoculated leaves showed symptoms of blight starting at 2 weeks after inoculation, and no symptoms appeared on the controls. On non-cold injured inoculated leaves, only one isolate caused symptoms (80% of all leaves). The fungus was re-isolated from diseased leaves. These results suggest that P. washingtonensis is able to cause foliar blight on Pacific madrone when leaves are subjected to cold stress. Increased disease severity on madrone observed in spring 2011 in Washington and Oregon may have been due to predisposition of foliage to extreme cold in November 2010 and February 2011. This fungus has previously been reported to cause a postharvest fruit rot disease on apple fruit and a canker and twig dieback disease of apple and crabapple trees in WA (1). To our knowledge, this is the first report of P. washingtonensis causing a leaf blight disease on Pacific madrone in North America. References: (1) C. L. Xiao et al. Mycologia 97:464, 2005. (2) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.

Botrytis cinerea has previously been shown to consist of two sibling species, referred to as Group I and Group II, that can be differentiated by PCR-RFLP analysis of the Bc-hch gene, a vegetative incompatibility locus (1). Group I has recently been described as a new cryptic species, B. pseudocinerea (4). Gray mold caused by B. cinerea is a major postharvest disease of blueberries in the Central Valley of California. In 2012 and 2013, blueberry fruit were sampled at harvest from various locations in the region and stored at 0 to 1°C for 5 weeks, and fungi were isolated from decayed fruit. In total, 526 isolates of Botrytis spp. were obtained. Genomic DNA was extracted and PCR-RFLP of a fragment of the Bc-hch gene was performed. Four isolates showed the distinctive restriction band pattern associated with Group I (1). The identity of these four isolates was further investigated by sequencing portions of four genes: internal transcribed spacer region, glyceraldehyde-3-phosphate dehydrogenase (G3PDH), heat-shock protein 60 (HSP60), and DNA-dependent RNA polymerase subunit II (RPBII), using the primers described previously (3,4). Sequences were deposited in GenBank (Accession Nos. KJ796643 to 58). BLAST analysis showed that sequences of all four genes for the four isolates were 99.8 to 100% similar to those of B. pseudocinerea. Morphological characteristics of the four blueberry isolates were examined as described previously (4). On potato dextrose agar, colonies were gray; the mycelial growth rate was 26 mm/day at 19°C in the dark. Conidiophores were simple and erect, and conidia were borne in grapelike clusters, one celled, hyaline, elliptical to ovoid, 6.5 to 15.7 × 5.6 to 9.8 μm (average of 7.4 × 10.1 μm). As reported previously, none of the morphological characters was able to differentiate between B. cinerea and B. pseudocinerea (4). To test pathogenicity, freshly harvested organic blueberry fruits were treated with 0.5% sodium hypochlorite for 2 min, rinsed with sterile water, wounded using a sterile needle, and inoculated by placing 1 μl of a conidial suspension (1.0 × 10 5 spores/ml) from each isolate into the wound with a pipette. Inoculated fruit (10 for each isolate) were incubated at 20°C for 5 days in the dark. Experiments were performed twice. All inoculated fruit developed rot, and no decay was observed on the noninoculated controls. All four isolates of B. pseudocinerea were pathogenic, and the fungus was re-isolated from decayed fruit. B. pseudocinerea isolates are known to be naturally insensitive to fenhexamid (1,4). Sensitivity of the four isolates to fenhexamid was examined in vitro as previously described (4). The EC 50 values for fenhexamid for the four isolates ranged from 7.7 to 9.9 μg/ml and isolates were considered resistant to fenhexamid (1,4). Based on the morphological, physiological, and genetic characteristics, the four blueberry isolates were identified as B. pseudocinerea. It appeared that this species was present at very low frequency (0.76%) in blueberry fields in California. Previously, B. pseudocinerea has been reported from French, German, and New Zealand vineyards (1,2,4). To our knowledge, this is the first report of B. pseudocinerea causing gray mold in blueberry in California and in North America. References: (1) E. Fournier et al. Mycologia 95:251, 2003. (2) P. R. Johnston et al. Plant Pathol. 63:888, 2014. (3) M. Staats et al. Mol. Biol. Evol. 22: 333, 2005. (4) A.-S. Walker et al. Phytopathology 101:1433, 2011.

Phacidiopycnis washingtonensis is the cause of speck rot, a recently reported postharvest fruit rot disease of apple. The pathogen is believed to incite infections in the field, and disease symptoms become evident only during storage. To determine the timing of apple fruit infection in relation to development of speck rot in storage, 'Red Delicious' and 'Fuji' apple fruit were inoculated in the orchard with P. washingtonensis at different times during the growing season, harvested, and monitored for decay development during storage at 0°C. Fruit inoculated in both field and laboratory also were used to identify the infection courts and mode of apple fruit penetration by P. washingtonensis. In all 3 years, stem-end speck rot and calyx-end speck rot developed during cold storage on fruit inoculated during the growing season, regardless of inoculation time; and the incidence of total speck rot in storage increased as the fruit inoculation time approached harvest. On fruit floral parts, the pathogen colonized sepals at higher rates than stamens. Availability of naturally occurring necrotic tissues favored the colonization of the fungus on sepals. Histological studies indicated that infection occurred through micro-cracks on the surfaces of pedicels and sepals of the fruit, and invasion of these tissues was restricted between the cuticle and epidermis. Findings of this study will assist in the development of effective control strategies for speck rot.

Sphaeropsis pyriputrescens is the cause of Sphaeropsis rot, a recently reported postharvest fruit rot disease of apple. Infection of apple fruit by the fungus is believed to occur in the orchard, and symptoms develop during storage or in the market. S. pyriputrescens also is the cause of a twig dieback and canker disease of apple and crabapple trees. To determine sources of pathogen inoculum in the orchard, twigs with dieback and canker symptoms, dead fruit spurs, dead bark, and fruit mummies on the trees were collected and examined for the presence of pycnidia of S. pyriputrescens. To monitor inoculum availability during the growing season from early May to early November, dead fruit spurs or twigs from Fuji trees, and twigs with dieback from crabapple trees (as a source of pollen for apple production) in a Fuji orchard as well as dead fruit spurs and dead bark from Red Delicious trees in a Red Delicious orchard were sampled periodically and examined for the presence and viability of pycnidia of S. pyriputrescens. To determine seasonal survival and production of pycnidia of the fungus on twigs, apple twigs were inoculated in early December, sampled periodically for up to 12 months after inoculation, examined for the presence of pycnidia, and subjected to isolation of the fungus from diseased tissues to determine its survival. Pycnidia of S. pyriputrescens were observed on diseased twigs, dead fruit spurs and bark, and mummified fruit on both apple and crabapple trees, suggesting that these tissues were the sources of inoculum for fruit infection in the orchard. With the combined observations from two orchards during three growing seasons, viable pycnidia of the fungus were present throughout the year and observed in 50 to 100% of the Fuji trees, >90% of crabapple trees, and 0 to 50% of the Red Delicious trees. S. pyriputrescens was recovered from diseased tissues of inoculated twigs at all sampling times up to 12 months after inoculation. The results suggest that S. pyriputrescens can survive as mycelium in diseased twigs in north-central Washington State and that availability of viable S. pyriputrescens pycnidia is unlikely a limiting factor for infection of apple fruit in the orchard leading to Sphaeropsis rot during storage.

Penicillium expansum is the cause of blue mold in stored apple fruit. In 2010-11, 779 isolates of P. expansum were collected from decayed apple fruit from five packinghouses, tested for resistance to the postharvest fungicide pyrimethanil, and phenotyped based on the level of resistance. In 2010, 85 and 7% of the isolates were resistant to pyrimethanil in packinghouse A and B, respectively, where pyrimethanil had been used for four to five consecutive years. In 2011, pyrimethanil or fludioxonil was used in packinghouse A, and 96% of the isolates from the fruit treated with pyrimethanil were resistant but only 4% of the isolates from the fruit treated with fludioxonil were resistant to pyrimethanil, suggesting that fungicide rotation substantially reduced the frequency of pyrimethanil resistance. No pyrimethanil-resistant isolates were detected in 2010 in the three other packinghouses where the fungicide had been used recently on a small scale. However 1.8% of the isolates from one of the three packinghouses in 2011 were resistant to pyrimethanil. A significantly higher percentage of thiabendazole-resistant than thiabendazole-sensitive isolates were resistant to pyrimethanil. Of the pyrimethanil-resistant isolates, 37 to 52, 4 to 5, and 44 to 58% were phenotyped as having low, moderate, and high resistance to pyrimethanil, respectively. Fludioxonil effectively controlled pyrimethanil-resistant phenotypes on apple fruit but pyrimethanil failed to control phenotypes with moderate or high resistance to pyrimethanil and only partially controlled the low-resistance phenotype.

Speck rot caused by Phacidiopycnis washingtonensis and Sphaeropsis rot caused by Sphaeropsis pyriputrescens are two recently reported postharvest diseases of apple. Infection by these two pathogens occurs in the orchard but remains latent before harvest. Symptoms develop after harvest and are similar to those of gray mold caused by Botrytis cinerea. Accurate diagnosis of these diseases is important during the fruit inspection process, particularly in the instance of fruit destined for export. Early near-harvest detection of latent infections in apple fruit is an important step to implement relevant pre- and postharvest measures for disease control. The aim of this study was to develop polymerase chain reaction (PCR) assays for diagnosis and early detection of latent infections of apple fruit by P. washingtonensis and S. pyriputrescens. Species-specific primers based on the ribosomal DNA internal transcribed spacer region were designed for use in PCR assays. Conventional and real-time PCR assays were developed and validated using fruit inoculated with P. washingtonensis, S. pyriputrescens, or B. cinerea and compared with identifications using traditional isolation-based assays. For wound-inoculated fruit, the PCR assays consistently provided the correct identification of the pathogen used as the inoculant in 6 h of processing time, compared with 5 to 6 days using culture-based methods. Real-time PCR assays effectively detected latent infections in symptomless stem and calyx tissues of fruit that were inoculated with the pathogens in the orchard during the growing season. The PCR assays provide a rapid, accurate method for diagnosis and early detection of these diseases.

In March 2012, decayed 'Empire' apple fruit (Malus × domestica Borkh.) were sampled from apples grown in Albion (Orleans County) in New York State and stored in bins for 6 months under controlled atmosphere at a commercial packinghouse. At the packinghouse following storage prior to be packed, the fruit were completely rotten, spongy to firm, and light brown without pycnidia. All fruit rots originated from either stem-end or calyx-end infections but no wound infections were observed. The incidence of fruit with these symptoms in the total decay was relatively low (0.1%). To isolate the causal agent, small fragments of fruit flesh from 12 decayed fruit were cut and placed on potato dextrose agar (PDA) acidified with 0.1% lactic acid. The plates were incubated at 20°C for 4 days and sub-cultured on PDA to obtain a pure culture. The colonies initially appeared with dense hyaline mycelium and later turned light yellow to yellow, and black pycnidia formed after about 2 weeks of incubation under a 24-h fluorescent light at 20°C. Conidia were light brown to brown, clavate to subglobose to irregular, and 15 × 8 μm on average. The fungus was identified as Sphaeropsis pyriputrescens Xiao & J.D. Rogers based on the morphology of the fungus (3). The identity of a representative isolate was further confirmed by analysis of nucleotide sequences of the internal transcribed spacer (ITS) regions amplified using the primers ITS1/ITS4. A BLAST search in GenBank showed that the sequence had 99% homology to an S. pyriputrescens sequence (Accession No. GQ374241). One representative isolate was tested for pathogenicity on apple fruit. Organic 'Red Delicious' apple fruit were surface-disinfected in 0.6% sodium hypochlorite solution for 5 min, rinsed twice with deionized water, and air-dried. Each fruit was wounded with a sterilized finish-nail head (3 mm in depth and 4 mm in diameter) and inoculated by placing a 4-mm-diameter plug from the leading edge of a 4-day-old PDA culture on the wound. Control fruit were treated with sterile PDA plugs. The inoculation site was covered with two layers of moist cheesecloth to avoid dehydration. There were four 10-fruit replicates for each treatment, and fruit were placed in plastic crispers and stored at 4°C for 4 weeks. The experiments were conducted twice. Sphaeropsis rot developed on all inoculated fruit, while no decays appeared on the control fruit. Koch's postulates were fulfilled by reisolating the fungus from the decayed fruit. Sphaeropsis rot is a recently reported postharvest fruit rot disease of apple and pear (1,3). The disease was first observed on 'd'Anjou' pears, and later more serious economic losses were observed in apples in Washington State (1). The disease has also since been reported in British Columbia, Canada (2). To the best of our knowledge, this is the first report of the occurrence of Sphaeropsis rot caused by S. pyriputrescens on apple in New York or in any region outside of the Pacific Northwest in North America. References: (1) Y. K. Kim and C. L. Xiao. Plant Dis. 92:940, 2008. (2) P. L. Sholberg et al. Plant Dis. 93:843, 2009. (3) C. L. Xiao et al. Plant Dis. 88:223, 2004.

Sphaeropsis rot caused by Sphaeropsis pyriputrescens is a recently reported postharvest fruit rot disease of apple grown in Washington State. The objective of this study was to develop chemical-based mitigation measures for Sphaeropsis rot in stored apple fruit. To determine in vitro sensitivity of S. pyriputrescens to the three registered postharvest fungicides thiabendazole, fludioxonil, and pyrimethanil, 30 isolates of S. pyriputrescens obtained from various sources were tested for mycelial growth and conidial germination on fungicide-amended media. Golden Delicious apple fruit were inoculated with the pathogen in the orchard at 2 or 5 weeks before harvest. After harvest, fruit were either nontreated or dipped in thiabendazole, fludioxonil, or pyrimethanil solutions, stored at 0°C, and monitored for decay development for up to 9 months after harvest. The mean effective concentration of a fungicide that inhibits mycelial growth or spore germination by 50% relative to the nonamended control (EC 50 ) values of thiabendazole, fludioxonil, and pyrimethanil on mycelial growth were 0.791, 0.0005, and 2.829 μg/ml, respectively. Fludioxonil and pyrimethanil also were effective in inhibiting conidial germination of the fungus with EC 50 values of 0.02 μg/ml for fludioxonil and 5.626 μg/ml for pyrimethanil. All three postharvest fungicides applied at label rates immediately after harvest were equally effective in controlling Sphaeropsis rot in stored apple fruit, reducing disease incidence by 92 to 100% compared with the nontreated control. The results indicated that Sphaeropsis rot may be effectively controlled by the currently registered postharvest fungicides thiabendazole, fludioxonil, and pyrimethanil.

Blue mold caused by Penicillium expansum is a major postharvest fruit rot disease of apples (Malus domestica) worldwide. Pyrimethanil was registered in late 2004 in the United States for postharvest use on apples. Since then, pyrimethanil has been increasingly used in Washington State as a postharvest drench treatment for control of blue mold and other postharvest diseases in apples. Baseline sensitivity to pyrimethanil in P. expansum populations from apples in Washington State has been established and all isolates in the baseline population were sensitive to pyrimethanil (1). To monitor resistance to pyrimethanil in P. expansum populations, blue mold-like decayed apple fruit were sampled from May to August 2009 from the fruit that had been drenched with pyrimethanil prior to storage from fruit packinghouses. Isolation of Penicillium species from decayed fruit was attempted. Isolates of Penicillium species were identified to species according to the descriptions by Pitt (2). In total, 186 P. expansum isolates were collected and tested for resistance to pyrimethanil in a conidial germination assay on an agar medium amended with pyrimethanil at the discriminatory concentration of 0.5 μg ml -1 (1). Isolates that were able to germinate were considered resistant to pyrimethanil. Of the 186 isolates tested, one was resistant to pyrimethanil. EC 50 (the effective concentration that inhibits fungal growth by 50% relative to the control) of pyrimethanil for the resistant isolate was determined according to a method described previously (1) and the test was done twice. EC 50 values of pyrimethanil on mycelial growth and conidial germination for the resistant isolate were 9.9 and 3.1 μg/ml, respectively, which were 7.4-fold and 16.5-fold higher than the means of the baseline population (1). To evaluate whether pyrimethanil at label rate is still able to control this resistant isolate, 'Fuji' apples were wounded, inoculated with conidial suspensions (1 × 10 4 conidia ml -1 ) of either the resistant isolate or a pyrimethanil-sensitive isolate, treated with either pyrimethanil or sterile water as controls, and stored at 20°C for 10 days following a method described previously (1). There were four 20-fruit replicates for each treatment. The experiment was performed twice. All inoculated fruit in the nontreated controls were decayed. Pyrimethanil applied at label rate completely controlled blue mold incited by a pyrimethanil-sensitive isolate, but 75% of the fruit that were inoculated with the resistant isolate and treated with pyrimethanil developed blue mold. To our knowledge, this is the first report of pyrimethanil resistance in P. expansum from decayed apple fruit collected from commercial packing houses. The pyrimethanil-resistant isolate was obtained from a packing house in which pyrimethanil had been used as a postharvest drench treatment in each of four consecutive years, suggesting that pyrimethanil-resistant individuals are emerging in P. expansum populations in Washington State after repeated use of pyrimethanil. Our results also indicate that pyrimethanil resistance in P. expansum reported in this study can result in failure of blue mold control in apples with pyrimethanil. References: (1) H. X. Li and C. L. Xiao. Postharvest Biol. Technol. 47:239, 2008. (2) J. I. Pitt. A Laboratory Guide to Common Penicillium species. Food Science Australia, North Ryde NSW, Australia, 2002.

Gray mold caused by Botrytis cinerea is a major postharvest disease of apple. Pristine, a formulated mixture of pyraclostrobin and boscalid, was recently registered for use on apple. Pristine applied within 2 weeks before harvest is effective in controlling gray mold in stored apple fruit. To determine the baseline sensitivity of B. cinerea populations to these fungicides, 40 isolates from organic and 80 from conventional apple orchards where Pristine had not been used were tested for mycelial growth or conidial germination on fungicide-amended media. To monitor fungicide resistance, gray-mold-decayed apple fruit originating from orchards in which Pristine had been used were sampled from a fruit packinghouse. Isolates of B. cinerea recovered from the fruit were tested for resistance to the two fungicides. In the in vivo study in the orchards, Pristine was applied to fruit 1 day before harvest. Fruit were then harvested, wounded, and inoculated with isolates exhibiting different fungicide-resistance phenotypes. Fruit were stored at 0°C for 8 weeks for decay development. The effective concentration that inhibits mycelial growth by 50% relative to the control (EC 50 ) values for sensitive isolates ranged from 0.008 to 0.132 μg/ml (mean = 0.043, n = 116) for pyraclostrobin and from 0.003 to 0.183 μg/ml (mean = 0.075, n = 117) for Pristine in a mycelial growth assay on potato dextrose agar. The EC 50 values of boscalid for sensitive isolates ranged from 0.065 to 1.538 μg/ml (mean = 0.631, n = 29) in a conidial germination assay on water agar. Four isolates were resistant to pyraclostrobin, with resistance factors (RFs) ranging from 12 to 4,193. Of the four pyraclostrobin-resistant isolates, one also was resistant to boscalid (RF = 14) and Pristine (RF = 373), and two exhibited reduced sensitivity to Pristine (RF = 16 and 17). The minimum inhibitory concentration for conidial germination (for boscalid) or mycelial growth (for pyraclostrobin and Pristine) of sensitive isolates was 5 μg/ml, which is thus recommended as a discriminatory concentration for phenotyping isolates for resistance to these fungicides. Of the 56 isolates obtained from decayed apple fruit that had been exposed to Pristine, 11 (approximately 20%) were resistant to both pyraclostrobin and boscalid and 1 was resistant only to pyraclostrobin. Of the additional 43 isolates obtained from decayed apple fruit originating from an organic orchard, 3 were resistant only to pyraclostrobin, 2 were resistant only to boscalid, and 2 were resistant to both fungicides. It appeared that there was no cross resistance between pyraclostrobin and boscalid because of the existence of isolates resistant only to either pyraclostrobin or boscalid. Pristine applied at label rate in the orchard failed to control gray mold on apple fruit inoculated with the Pristine-resistant isolates. This is the first report of multiple resistance to pyraclostrobin, boscalid, and Pristine in field populations of B. cinerea. Our results suggest that the development of dual resistance to pyraclostrobin and boscalid in B. cinerea populations could result in the failure to control gray mold with Pristine.

Phacidiopycnis rot, caused by Potebniamyces pyri, is a recently recognized postharvest fruit rot disease of 'd'Anjou' pear (Pyrus communis) in the United States. To determine the timing of fruit infection in the orchard in relation to incidence of Phacidiopycnis rot during storage, fruit were inoculated in the orchard at different times during the growing season, harvested, and monitored for decay development during storage at 0°C. Fruit inoculated in the field and laboratory were also used to determine the infection courts and the importance of necrotic tissues to infection of sepals that may lead to calyx-end Phacidiopycnis rot. Phacidiopycnis rot was observed during cold storage on the fruit inoculated any time after bloom till near harvest but not on the fruit inoculated during bloom. Phacidiopycnis rot symptoms only developed at the stem and calyx end of the fruit during storage. Relatively more calyx-end rot was observed than stem-end rot on the fruit inoculated before August. Incidence of stem-end rot increased significantly on the fruit inoculated near harvest. Incidence of total Phacidiopycnis rot increased as the timing of fruit infection in the orchard approached harvest. Potebniamyces pyri was recovered more frequently from sepals than from styles and stamens of the fruit. Most infections on sepals were associated with the necrotic tissues. Naturally occurring necrotic tissues occurred on more than 85% and all sepals in the early fruit-growing and late growing seasons, respectively. Such necrotic tissues on sepals could serve as potential infection sites for P. pyri. The results may suggest that chemical control of Phacidiopycnis rot should focus on protecting the pedicel (stem) and floral parts of fruit and that fungicides applied near harvest are likely most important in controlling latent infections of pear fruit by P. pyri leading to Phacidiopycnis rot during storage.

Blue mold caused by Penicillium expansum is a major postharvest disease of apples (Malus × domestica). Residual activity of fludioxonil and pyrimethanil in apple fruit against P. expansum was investigated during 2005 to 2008. Fruit of the cultivar Delicious harvested from commercial orchards where fungicides were not used were either not treated or drenched with fludioxonil, pyrimethanil, or thiabendazole prior to storage and then stored in controlled atmosphere at 0°C for 5 or 7 months, after which time the fruit were removed from storage and subjected to washing and brushing, practices that are done at the time of packing. Fruit were then wounded and inoculated with conidial suspensions of P. expansum. Inoculated fruit were treated with either sterile water or fungicides. Fruit were stored at 0°C for 8 weeks and at room temperature for one additional week after cold storage. To determine distribution of fungicide residues in the fruit flesh, fruit were cut horizontally at the equator, sprayed with the conidial suspension of P. expansum, incubated at room temperature, and examined for inhibition of blue mold on the cut fruit 4 days after inoculation. Fungicide residues on/in the fruit were analyzed using a gas chromatograph. Zero to 26% blue mold incidence was observed on fludioxonil-drenched fruit that were inoculated and not treated with fungicides at packing. No decay or <4% blue mold incidence was observed on pyrimethanil-drenched fruit that were inoculated and not treated with fungicides at packing, whereas 65 to 99% blue mold incidence was observed on thiabendazole-drenched fruit that were not treated with fungicides at packing. An average of >32 mm inhibition zone and approximately 5 mm inhibition zone measured from the fruit peel toward the fruit core were observed on pyrimethanil-drenched and fludioxonil-drenched fruit, respectively. Washing and brushing at the time of packing 5 and 7 months after harvest did not remove or only partially removed residues of fludioxonil and pyrimethanil from apple fruit. The results suggest that residues of fludioxonil and pyrimethanil on/in apple fruit are persistent and that residual protection of apple fruit by the two fungicides can last for at least 7 months under apple-storage conditions.

After harvest, apples (Malus × domestica) may be kept in cold storage for up to 12 months prior to packing. Gray mold caused by Botrytis cinerea and blue mold caused by Penicillium expansum are common postharvest fruit rot diseases affecting apples and are controlled commonly by applications of fungicides after harvest. To search for an alternative strategy, Pristine (a premixed formulation of boscalid and pyraclostrobin) as a preharvest treatment was evaluated for control of postharvest gray mold and blue mold in cultivars Fuji and Red Delicious apples during 2004 to 2006. Pristine (0.36 g per liter of water) was applied 1, 7, or 14 days before harvest. For comparison, thiram (2.04 g per liter of water) was applied 7 days before harvest and ziram (2.4 g per liter of water) was applied 14 days before harvest, to Fuji and Red Delicious, respectively. Fruit were harvested at commercial maturity, wounded with a finishing nail head, inoculated with conidial suspensions of either B. cinerea or P. expansum, stored in air at 0°C, and evaluated for decay after 8 or 12 weeks. In 2004 and 2005, Pristine was equally effective when applied to Fuji 1 or 7 days before harvest, reducing gray mold incidence by 93 to 99% and blue mold incidence by 78 to 94% compared with the nontreated control. Thiram reduced gray mold incidence by 38 to 85%. Thiram reduced blue mold incidence by 22% in 2004 but not in 2005. On Red Delicious, Pristine was equally effective when applied 7 or 14 days before harvest and reduced gray mold incidence by 69 to 85% and blue mold incidence by 41 to 70%. Ziram applied 2 weeks before harvest reduced gray mold incidence by 97 and 94% in 2005 and 2006, respectively, but it did not reduce blue mold incidence. The results indicate that Pristine applied within 2 weeks before harvest may be an effective alternative to postharvest fungicides for control of postharvest gray mold and blue mold in Fuji and Red Delicious apples.

Sphaeropsis rot, caused by Sphaeropsis pyriputrescens, is a recently recognized postharvest disease of apple in Washington State. To determine the distribution and incidence of this disease as well as other postharvest diseases, decayed fruit were sampled during packing or pre-sizing operations in commercial fruit packinghouses from 26, 72, and 81 grower lots in 2003, 2004, and 2005, respectively. Fungi associated with decayed fruit were isolated and identified. The most common postharvest diseases of apple in the region were blue mold caused by Penicillium spp., primarily P. expansum, gray mold caused by Botrytis cinerea, and Sphaeropsis rot, accounting for 32, 28, and 17% of the decayed fruit, respectively. Percentages of these diseases in the total decayed fruit varied from lot to lot. Bull's eye rot caused by Neofabraea spp. was responsible for 13.4% of the total decay and was most prevalent on Golden Delicious. Other minor diseases included speck rot caused by Phacidiopycnis washingtonensis, Alternaria rot caused by Alternaria spp., Mucor rot caused by Mucor piriformis, and core rot caused by a group of fungi, primarily Alternaria spp. Sphaeropsis stem-end rot was more common than calyx-end rot on Golden Delicious, whereas Sphaeropsis calyx-end rot was more common than stem-end rot on Fuji. On Red Delicious, both stem-end rot and calyx-end rot were common. Sphaeropsis rot resulting from infections through the fruit peel was more commonly seen on Golden Delicious and Fuji than on Red Delicious. The percentage of gray mold was higher on nondrenched fruit than on fruit drenched with thiabendazole (TBZ), whereas blue mold was more prevalent on TBZ-drenched fruit. Our results indicate that Sphaeropsis rot is an important component of storage rots of apples in Washington State.

During a survey of postharvest diseases in Red Delicious apples (Malus domestica) conducted in 2003, a previously undescribed postharvest fruit rot was discovered in Washington State. The causal agent has been described as a new species, Phacidiopycnis washingtonensis. In this study, we described the symptomatology of this disease, determined its occurrence and prevalence in Washington State, tested pathogenicity, and determined infection courts on fruit of three apple varieties. Decayed fruit were sampled from 26, 72, and 81 grower lots during March to August in 2003, 2004, and 2005, respectively, during packing operations from commercial packinghouses. Symptoms of decayed fruit were recorded and isolations were made from decayed fruit to correlate causal agents with the disease symptoms observed. Fruit of Red Delicious, Golden Delicious, and Fuji apples were inoculated in the orchards with conidial suspensions of the fungus at 1 and 2 weeks before harvest. All fruit were harvested and stored at 0°C, and decay development on the fruit was monitored monthly for up to 9 months. The symptoms were primarily stem-end rot and calyx-end rot. Infection also occurred at lenticels on fruit skin, particularly on Golden Delicious. The decayed area was spongy to firm and appeared light brown to brown. On Red Delicious, brown to black specks at lenticels often appeared at the decayed area as the disease advanced. This disease occurred in 23, 26, and 17% of the total grower lots, accounting for approximately 1, 4, and 3% of the total decay in 2003, 2004, and 2005, respectively. In 2004 and 2005, severe losses of fruit were observed in three grower lots of Red Delicious, and their losses were as high as 24%. After 9 months in storage, 48, 48, and 24% of Red Delicious, Golden Delicious, and Fuji that were inoculated in the orchards, respectively, developed symptoms of this disease, and the fungus was reisolated from decayed fruit. Stem-end rot was common on Red Delicious and Golden Delicious, whereas calyx-end rot was common on Fuji. We propose "speck rot" as the name of this disease.

Crabapple (Malus sylvestris) is commonly used as a source of pollen in apple production. During September and October 2003, a canker and twig dieback disease of 'Manchurian' crabapple trees was observed in some commercial apple (Malus × domestica Borkh.) orchards (7- to 10-years-old) in north-central Washington State. A fungus was consistently isolated from 40 to 77% of sampled crabapple trees. During May 2004, the same symptoms and fungal association were observed in an 8-year-old 'Fuji' apple orchard in which all crabapple pollenizers and 43% of the Fuji trees were diseased. Canker and dieback appeared to originate from infection of dying or dead fruit spurs or pruning wounds. Cankered areas were slightly sunken, brown and the margin of diseased area often developed cracks in the cortical tissue. Pycnidia were often present in older areas of the lesion. Pycnidia were black, 0.3 to 0.6 mm in diameter, separate to aggregated in small numbers, and partially immersed to nearly superficial in the diseased tissue. To isolate the fungus, outer bark tissues of diseased twigs were scraped and small tissue segments were cut from the canker margin. Tissue segments were surface disinfested for 5 min in 0.5% sodium hypochlorite solution, rinsed three times with sterile water, cut into small pieces, and placed on acidified potato-dextrose agar (APDA, 4.0 ml of a 25% solution of lactic acid per liter of medium). Isolation plates were incubated at 20°C in the dark. Colonies of the fungus first appeared as dense colorless mycelium that later turned light yellow to yellow. The fungus was identified as Sphaeropsis pyriputrescens Xiao & J. D. Rogers (1). To complete Koch's postulates, two isolates (one each from apple and crabapple) were used in pathogenicity tests on 'Fuji' apple and 'Manchurian' crabapple trees. In the orchard, selected 2-year-old twigs were sprayed with 70% ethanol and allowed to dry. Twigs were wounded to a depth of 1 to 2 mm with a sterile 5-mm-diameter cork borer; a 5-mm mycelial plug from 4-day-old PDA cultures of S. pyriputrescens was placed into each wound. Twigs wounded and treated with sterile APDA plugs were used as controls. Inoculation sites were covered with moist cheesecloth and sealed with Parafilm that was removed 3 weeks after inoculation. Four twigs per isolate on each of four trees were inoculated. The experiment was conducted twice (April and November 2004 for apple; two different locations in March 2004 for crabapple). At 2 and 6 months after inoculation, two apple twigs per treatment were removed from each tree. All crabapple twigs were removed 2 months after inoculation. Canker sizes were measured and reisolation of the fungus was attempted as described above. Both isolates caused cankers on apple and crabapple twigs. Mean canker sizes at 6 months after inoculation were 11 and 32 mm on apple twigs inoculated in April and November 2004, respectively and 7 to 8 mm on crabapple twigs at 2 months after inoculation. No cankers developed on control twigs. S. pyriputrescens was reisolated from all inoculated twigs and was not recovered from noninoculated controls. S. pyriputrescens is the cause of Sphaeropsis rot, a recently reported postharvest fruit rot disease of apple and pear (1,2). To our knowledge, this is the first report of this fungus causing cankers and twig dieback on apple and crabapple trees. Reference: (1) C. L. Xiao and J. D. Rogers. Plant Dis. 88:114, 2004. (2) C. L. Xiao et al. Plant Dis. 88:223, 2004.

Winter pears (Pyrus communis) in the United States are produced primarily in the Pacific Northwest. Potebniamyces pyri (anamorph Phacidiopycnis piri) is the causal agent of Phacidiopycnis rot, a recently reported postharvest disease on pears in the United States. Infection of fruit by P. pyri occurs in the orchard, and symptoms develop during storage. P. pyri was observed to be associated with cankers, dead bark, and twig dieback of pear trees. P. pyri was isolated from 40 to 50% of the twig samples exhibiting dieback symptoms from three commercial d'Anjou pear orchards, and 35% of dying bark samples from one orchard. However, little information is available regarding pathogenicity of P. pyri on pear trees. To determine the distribution of P. pyri, dying and dead bark samples were collected from pear orchards in various pear-producing areas in Oregon and Washington, and examined for presence of fruiting bodies (pycnidia or apothecia) of P. pyri. In the orchard, 2-year-old twigs were wounded using a sterile cork borer with or without spraying with a commercial aerosol tissue-freezing product at the wound sites. Wounds were then inoculated with either mycelial plugs from an agar medium or conidial suspensions of P. pyri. In a separate experiment, freshly made pruning wounds were inoculated with conidial suspensions of P. pyri. Canker development was monitored approximately monthly for up to 6 months after inoculation, at which time reisolation of P. pyri was attempted. P. pyri was found to be widespread in the Pacific Northwest. Incidence of trees infected by P. pyri based on presence of viable pycnidia in pear orchards ranged from 0 to 100%. Monthly tree inoculations in the orchard indicated that P. pyri in general did not cause cankers on non-cold-injured, wound-inoculated twigs, but apparently became established on cold-injured, wound-inoculated twigs and caused small cankers. Minor dieback developed on twigs inoculated at pruning wounds. At 6 months after inoculation, P. pyri was recovered from the majority of inoculated twigs. Thus, P. pyri appears to be a weak canker-causing pathogen on pear trees.

Phacidiopycnis rot, caused by Phacidiopycnis piri, is a newly recognized postharvest disease in pear fruit (Pyrus communis cv. d'Anjou) in the United States. To determine the prevalence and incidence of this disease, decayed fruit were sampled during packing and repacking operations from four packinghouses in 2001 and 2002. During March to May (repacking) in 2001, Phacidiopycnis rot was found in packed fruit that were stored in cardboard boxes from 22 of 26 grower lots (orchards), and accounted for 5 to 71% of the total decay. Phacidiopycnis rot, gray mold caused by Botrytis cinerea, and blue mold caused by Penicillium spp. accounted for an average of 34.1, 10.3, and 33.6% of decayed fruit from conventional orchards, respectively; and 22.8, 35.7, and 23.5% of decayed fruit from organic orchards, respectively. During November 2001 to January 2002 (packing), Phacidiopycnis rot was observed in fruit that were stored in field bins before packing from 30 of 33 grower lots, accounting for 18.4% of decayed fruit sampled. During March to May in 2002, Phacidiopycnis rot was responsible for 2 to 68% of decayed fruit sampled from 36 of 39 grower lots. Phacidiopycnis rot, gray mold, and blue mold accounted for an average of 19.6, 26.8, and 37.4% of decayed fruit from conventional orchards, respectively; and 42.2, 25.7, and 8.2% of decayed fruit from organic orchards, respectively. Most Phacidiopycnis rot that occurred in field bins before packing appeared to originate from wound infections; whereas after packing, approximately 60 and 30% of Phacidiopycnis rot originated from stem and calyx infections, respectively. This study indicates that Phacidiopycnis rot should be considered one of the targets for control of postharvest diseases in d'Anjou pears in the region.

During a survey of postharvest diseases in stored pears conducted in the 2001-02 storage season, a new postharvest fruit rot in d'Anjou pears was discovered in Washington State. Symptoms of this disease were stem-end rot, calyx-end rot, and wound-associated rot, which presumably originated from infections of stem, calyx, and wounds on the fruit surfaces, respectively. The decayed area on the fruit was firm or spongy and appeared brown. During the late storage period from March to May 2002, this disease was observed in 19 of 39 lots and accounted for 2 to 21% of all decayed fruit. The causal agent, Sphaeropsis sp., was consistently recovered from decayed fruit with the symptoms described above. Two isolates of the fungus were used for pathogenicity tests on pear fruit. Decay symptoms developed on fruit inoculated with spore suspensions of the fungus on the stem, calyx, and wounds on the fruit surface. The fungus was reisolated from these decayed fruit. The fungus, Sphaeropsis pyriputrescens sp. nov., was characterized and described. On potato dextrose agar (PDA), oatmeal agar, and pear juice agar at 20°C, the fungus grew at mean rates of 21, 15, and 24 mm day -1 in colony diameter, respectively. On PDA, the fungus formed a circular colony with dense, hyaline hyphae and a few or some aerial mycelia. Colonies appeared light yellow to yellow on 2-week-old PDA cultures. The fungus grew at temperatures from 0 to 25°C, with optimum growth between 15 and 20°C, little or no growth at 30°C, and no growth at 35°C. This is a low-temperature species.

During March to July 2003, a postharvest fruit rot was observed on 'Golden Delicious', 'Granny Smith', and 'Red Delicious' apples (Malus × domestica Borkh.) sampled from commercial packinghouses in Washington State. Losses as high as 24% in storage bins were observed in July on 'Red Delicious'. The disease started at the stem bowl area or the calyx end of the fruit. Decayed fruit was apparently not wounded. Decayed areas were brown and firm. Internal decayed flesh appeared yellowish brown. On 'Red Delicious' apples, decayed fruit was apparently discolored from red to brown. As the disease advanced, pycnidia of a fungus might form on the stem, sepals, or the surface of decayed fruit. Pycnidia were 0.3 to 0.7 mm in diameter, black, and partially immersed in decayed tissues. To isolate the causal agent, decayed fruit was lightly sprayed with 70% ethanol and air dried. Fragments of diseased tissue were removed from the margin of diseased and healthy tissue and plated on acidified potato dextrose agar (PDA). A fungus was consistently isolated from decayed fruit with the symptoms described above. On PDA, the colonies of the fungus first appeared with dense hyaline mycelium and later turned light yellow to yellow. Black pycnidia of the fungus formed on 2- to 3-week-old oatmeal agar cultures at 20°C under 12-h alternating cycles of fluorescent light and dark. The fungus was identified as Sphaeropsis pyriputrescens Xiao & J. D. Rogers, based on the description of the fungus (1). Voucher specimens were deposited at the WSU Mycological Herbarium. Two isolates of the fungus recovered from decayed apples were tested for pathogenicity on apple. Fruit of 'Golden Delicious' and 'Gala' were surface-disinfested for 5 min in 0.5% NaOCl, rinsed, and air dried. Fruit was wounded with a sterile 4-mm-diameter nail head. A 4-mm-diameter plug from the leading edge of a 3-day-old PDA culture or plain PDA (control) was placed in the wound of each of 10 replicate fruit for each isolate or control. Fruit was tray packed with polyethylene liners and stored in cardboard boxes in air at 3°C, and decay was evaluated 2 weeks after inoculation. Five decayed fruits from each treatment were selected for reisolation of the causal agent. The experiment was conducted twice. In a separate pathogenicity test, two isolates (one each from apple and pear) were included in the test. Fruit of 'Red Delicious' apple was prepared and inoculated as the same manner described above, but fruit was stored in air at 0°C. The experiment was conducted twice. All fruit that were inoculated with the fungus developed decay symptoms. No decay developed on fruit in the controls. The same fungus was reisolated from decayed fruit. This indicates that isolates from apple and pear were pathogenic to apple. S. pyriputrescens is the causal agent of a newly reported postharvest disease on 'd'Anjou' pears (1). To our knowledge, this is the first report of this fungus causing postharvest fruit rot on apple. We propose 'Sphaeropsis rot' as the name of this new disease on apple and pear. Preliminary evidence suggests that infection of fruit by this fungus occurred in the orchard prior to storage. Reference: (1) C. L. Xiao and J. D. Rogers. Plant Dis. 88:114, 2004.

A plant yield and disease incidence uniformity trial was conducted to provide information concerning the efficiency and precision of field trials used to evaluate Botrytis fruit rot control methods on strawberry. Fruit yield and Botrytis fruit rot incidence were recorded for individual strawberry plants of cultivars Sweet Charlie and Camarosa grown in an annual production system over two growing seasons. A nested analysis of variance model was used to measure plot edge effects and to obtain variance components to describe the relationship between plot size and plot variance. Mean seasonal yield for Sweet Charlie was 599 g/plant and for Camarosa 972 g/plant. Mean seasonal fruit rot incidence was 10.3% for Sweet Charlie and 3.0% for Camarosa. Plants growing on the edge of plots next to aisles had higher yields (637 versus 577 g/plant for Sweet Charlie and 1047 versus 923 g/plant for Camarosa), but there was no edge effect for disease incidence. Smith's equation was used to determine the relationship between plot size and plot variance within mulched beds. Smith's index was relatively high for yield (0.92 and 0.95) and Botrytis fruit rot incidence (0.91 and 0.69) for Sweet Charlie and Camarosa, respectively. This suggests a relatively uniform distribution of seasonal yield and disease incidence among plants within beds. Using plot variances estimated from Smith's equation, the power of hypothesis tests to discriminate hypothetical treatment effects of different magnitudes was examined for each cultivar. Power analysis suggests that treatment effects ranging from 11.3 to 21.3% of the mean seasonal yield observed for Sweet Charlie and 8.6 to 16.5% of the mean seasonal yield observed for Camarosa can be detected with a power of 0.80 using four replicates of each treatment group and plot sizes ranging from 32 to eight plants/plot. For Botrytis fruit rot incidence, a power of 0.80 is achieved with treatment differences ranging from 24.9 to 44.1% of mean seasonal Botrytis fruit rot incidence for Sweet Charlie and from 44.1 to 64.9% of the mean observed for Camarosa using plot sizes ranging from 32 to 8 plants/plot. Before planting, the crown diameter and leaf number of transplants were recorded. There was no consistent significant correlation between any of these growth traits and seasonal yields or Botrytis fruit rot incidence. However, there was a consistent positive correlation for both cultivars between yield and crown diameter and also yield and leaf number during the months of December and January in the early part of the season (0.1513 ≤ r ≤ 0.314 for crown diameter and 0.106 ≤ r ≤ 0.264 for leaf number).

Epidemics of Botrytis fruit rot (Botrytis cinerea) and powdery mildew (Sphaerotheca macularis f. sp. fragariae) in annual strawberry were compared in large plastic tunnel and field production systems during the 1998-99 and 1999-2000 seasons. Treatments were factorial combinations of two main plots (field and tunnel) and four subplots, including combinations of two cultivars (Camarosa and Sweet Charlie) and two captan schedules arranged in a split-plot design with three replications. The mean incidence of Botrytis fruit rot was 88 to 94% lower in tunnels than in the field. The incidence of Botrytis fruit rot for the untreated control in tunnels was less than 2%, which was 89% lower than that of the 7-day captan schedule in the field. This indicates that Botrytis fruit rot can be controlled effectively without fungicides in a tunnel cultural system. Powdery mildew was severe on susceptible cultivar Camarosa in tunnels. Early season yields of cultivar Sweet Charlie were significantly higher in tunnels than in the field. Shorter periods of leaf wetness and higher temperatures in tunnels may have contributed to a lower incidence of Botrytis fruit rot and a higher incidence of powdery mildew on fruit in tunnels compared with open field plots.

The control of postharvest Botrytis fruit rot was evaluated during 1997-98 and 1998-99. Weekly applications of captan and thiram were examined at two or three different rates, respectively. Iprodione applications were combined with the captan and thiram treatments and also applied alone for two peak bloom periods. Strawberry fruit were harvested and graded twice weekly for marketable yield and preharvest incidence of Botrytis fruit rot. For postharvest evaluations, fruit from four harvests were selected and stored at 4°C, and Botrytis fruit rot incidence was recorded over 14 days of storage. Fungicide treatments reduced the incidence of preharvest Botrytis fruit rot and increased marketable yield. The incidence of postharvest Botrytis fruit rot was significantly affected by harvest date, length of time in storage, and fungicide treatment. The highest rate captan and thiram treatments had the least Botrytis fruit rot and the longest storage life. Reduced-rate captan and thiram treatments generally did not provide the same control as their respective high-rate treatments. Iprodione added to either the captan or thiram treatments did not consistently reduce the preharvest or postharvest incidence of Botrytis fruit rot or increase yield. Regular, full-rate fungicide treatments appear to be necessary to control Botrytis fruit rot in Florida and to provide the storage life necessary to reach distant markets.

The management of Botrytis fruit rot on annual strawberry by fungicides was evaluated in Florida during the 1995-96, 1996-97, and 1997-98 seasons. Weekly applications of captan or thiram, bloom applications of iprodione applied twice during each of two peak flowering periods, and weekly applications of captan combined with iprodione bloom applications were evaluated. Significant treatment effects (P ≤ 0.05) on the incidence of Botrytis fruit rot were detected for the early, late, and whole-season periods each season. Weekly applications of captan or thiram controlled Botrytis fruit rot, reducing disease incidence by more than 41% compared to the untreated control. These treatments also affected marketable yield during two seasons, with a 42 to 127% increase in yield compared to the control. Weekly fungicide applications did not reduce the incidence of Botrytis fruit rot until at least the fourth week of harvest, 9 to 10 weeks after applications began. Bloom applications of iprodione alone reduced the incidence of Botrytis fruit rot during the second peak bloom period, and the reductions in incidence occurred 1 to 3 weeks after the start of bloom applications. This suggests that iprodione applications control infections at flowering or early stages of fruit development. However, early-season bloom applications did not reduce the incidence of Botrytis fruit rot. The control of Botrytis fruit rot by weekly captan applications was not improved by the addition of iprodione bloom applications. These data suggest that early-season fungicide applications for the control of Botrytis fruit rot in annual winter strawberry are of limited efficacy, and that bloom applications of Botryticides such as iprodione should be focused on the second peak bloom period.

To determine the effects of sanitation on yield and incidence of Botrytis fruit rot (Botrytis cinerea) in annual strawberry, replicated experiments were conducted during the 1995-96, 1996-97, and 1998-99 seasons. Leaf sanitation (removal of senescent and necrotic leaves) and fruit sanitation (removal of unmarketable fruit from alleys between beds) were compared to a standard fungicide control program (weekly applications of captan plus four bloom applications of iprodione) and combined sanitation and fungicide treatments. Leaf sanitation reduced Botrytis fruit rot incidence from 12.6 to 8.2% over the entire 1996-97 season, and from 17.6 to 11.8% during the latter half of the 1998-99 season, compared to untreated controls. However, sanitation did not increase marketable yield. Supplementing fungicides with leaf sanitation or leaf and fruit sanitation did not improve disease control and frequently reduced yield. Fruit sanitation had no significant effect on Botrytis incidence or yield. Losses to Botrytis fruit rot in the sanitation treatments were significantly higher (P ≤ 0.05) than in the fungicide treatments each season; marketable yields were significantly lower in 1996-97 and 1998-99. Under Florida conditions, fungicides control Botrytis fruit more effectively and economically than does sanitation.

Evaluating fungicide efficacy in annual strawberry production systems can be labor intensive due to continuous harvesting over a relatively long season. The effect of reduced harvest number on the accuracy of least significant difference (LSD) separations for Botrytis fruit rot (Botrytis cinerea) incidence and marketable yield in fungicide efficacy studies was evaluated over three seasons. Fruit were harvested and graded twice a week for a total of 23 to 32 harvests each season. Data from each season were divided into different sample sets. Data from three different harvest periods (early, late, and whole season) and different harvesting frequencies (twice weekly, once weekly, every second, third, or fourth week) were compared with the complete data set (twice weekly for the whole season). Spearman's rank correlation and Pearson's product moment correlation coefficients were used to evaluate the correlation of the complete data sets with data sets from other sampling plans. Harvesting once a week for either the late- or whole-season periods accurately estimated LSD groupings for Botrytis fruit rot incidence among fungicide treatments. The precision of marketable yield estimates using once-a-week harvesting for the late or whole-season periods were relatively lower than for the incidence of Botrytis.

The effects of within-row plant spacing and cultivar on the incidence of Botrytis fruit rot (Botrytis cinerea) and marketable yield of annual strawberry were evaluated during the 1997-98 and 1998-99 seasons. Three cultivars (Camarosa, Rosa Linda, and Sweet Charlie) and four plant spacings (23, 30, 38, and 46 cm) were evaluated. Marketable yield and the incidence of Botrytis fruit rot were determined twice weekly. Cultivar and spacing effects were analyzed for three periods each season (early, late, and whole season). In 1997-98, spacing effects were observed on weekly incidence of Botrytis rot for the late period (P = 0.0925) and on cumulative incidence for the whole season period (P = 0.0795). Further analysis of the late and whole season periods revealed a spacing effect for Camarosa (P = 0.0102). Spacing also had a dramatic effect on cumulative and weekly Botrytis incidence for the late and whole season periods during the 1998-99 season (P ≤ 0.0014), when narrower spacings had higher incidence of Botrytis than wider spacings. Marketable yields were higher at narrower spacings during the early period for both seasons. Whole season marketable yields were also higher at the narrower spacings despite higher incidence of Botrytis. There were significant differences in susceptibility among cultivars.