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Apple bitter rot is caused by Colletotrichum nymphaeaeand other Colletotrichumspecies and management relies primarily on synthetic pesticides. Very few fungicides are effective against the disease and resistance has further limited their usefulness. A recent study indicated a range of EC50values (the concentration required to inhibit 50% of mycelial growth in vitro) of C. nymphaeaeisolates from Brazilian apples to fluazinam and tebuconazole, two fungicides that are not routinely used for bitter rot control. Isolates on opposite sides of the sensitivity range were designated sensitive (low EC50values) and reduced-sensitive (high EC50values). The objective of this research was to confirm stability of EC50values after storage, assess fluazinam and tebuconazole efficacy against reduced-sensitive isolates for apple bitter rot management in detached fruit studies, and to sequence the fungicide’s putative target genes. Our research confirmed stability of EC50values after 8 months of cold storage. Detached fruit studies revealed that protective treatment of cv. Gala apple fruit with fluazinam and tebuconazole controlled both sensitive and reduced-sensitive phenotypes but if used curatively (after infection) reduced-sensitive isolates were controlled less effectively. The complete OS-1, CYP51A, and CYP51Bgenes from C. nymphaeaeisolates sensitive or reduced-sensitive to fluazinam (potential target OS-1) and tebuconazole (CYP51Aand CYP51B) were sequenced. This study underscores the potential usefulness of fluazinam and tebuconazole for bitter rot control of apple but also indicates weaknesses when products were to be applied post infection.

Previous studies have demonstrated the efficacy of calcium (Ca) spray applications derived from Ca chloride for reducing botrytis (Botrytis cinerea) infection severity on petunia (Petunia ×hybrida) flowers. This study examines the effects of six Ca sources for their efficacy in reducing Botrytis blight on petunia flowers and their potential to cause spray damage or phytotoxicity. In the first experiment, the six Ca sources evaluated were laboratory-grade and commercialgrade Ca chloride, Ca nitrate, Ca ethylenediaminetetraacetic acid chelate, Ca amino acid chelate, and Ca silicate. In the second experiment, petunia flowers that were 0, 1, 3, 5, or 7 days old at the time of the Ca spray applications were evaluated for spray damage severity. For both experiments, treatments were applied to flowering plants. For the evaluation of Botrytis blight efficacy, flowers were excised and inoculated with botrytis spores 24 hours after the Ca spray application, and were evaluated every 12 hours for 72 hours. Laboratory-grade and commercial-grade Ca chloride at 1250 mg.L-1 Ca were the most effective Ca sources evaluated for decreasing Botrytis blight severity while not causing spray damage at any flower age. Spray damage to the flowers from the Ca chloride application increased when Ca concentrations increased to 2000 mgL.-1, but no additional benefit was observed for reducing Botrytis blight severity compared with the 1250-mg.L-1 Ca application. The results demonstrate that several Ca sources reduce Botrytis blight severity significantly; however, selection of the Ca source is important for minimizing the risk of spray damage. [ABSTRACT FROM AUTHOR]

Anthracnose fruit rot is one of the main diseases affecting strawberries especially in warm and humid climates. In commercial settings, producers are relying on fungicides to control the disease. One of the most potent chemical classes of fungicides for anthracnose control are the quinone outside inhibitors (QoIs), but resistance in field isolates due to a point mutation in the target gene cytbhas recently been reported in multiple states of the USA. During a routine screening, two Colletotrichum nymphaeaeisolates (OH_S1 and OH_S2) obtained from strawberry plants of a commercial field in Marietta-Ohio were found to be resistant to QoI fungicide azoxystrobin. The EC50values determined in poison agar tests were greater than 100 μg/L. Both isolates were not controlled on detached strawberry fruit treated with label rates of Abound fungicide (a.i. azoxystrobin) and revealed disease severity of 86% and 96% on detached fruit. A baseline isolate (Cn_ebel2) of the same species revealed an EC50value of 1.2 μg/L and no disease developed on Abound-treated fruit. In contrast to other reports, sequencing of the cytbgene from all three isolates used in this study revealed no amino acid changes in cytb, indicating the existence of a different and still unknown resistance mechanism.

Blackberry fruits symptomatic for gray mold were collected from three commercial blackberry fields in northwestern South Carolina. Single-spore isolates were generated and two distinct phenotypes were discovered in each location; one sporulated on PDA and one did not. One isolate of each phenotype and location (six isolates total) were selected for in depth molecular and morphological characterization. Glyceraldehyde-3-phosphate dehydrogenase (G3PDH), heat-shock protein 60 (HSP60) and DNA-dependent RNA polymerase subunit II (RPB2) coding sequence alignment revealed Botrytis cinereaas the sporulating phenotype and a new yet undescribed species as the non-sporulating phenotype. The new Botrytissp., described herein as Botrytis caroliniana, was most closely related genetically to B. fabiopsisand B. galanthina, the causal agents of gray mold disease of broad bean and snowdrop, respectively. It produces smaller conidia than either B. fabiopsisor B. galanthina, and sequence analysis of genes encoding necrosis and ethylene-inducing proteins (NEPs) also indicated that the Botrytisisolates represent a separate and distinct species. The new species is pathogenic on blackberry fruits and broad bean leaves, which distinguishes it further from B. galanthina. The new species formed white to pale gray colonies with short, tufted aerial mycelium and produced black sclerotia on PDA at 20 C. To our knowledge this is only the third Botrytisspecies discovered to cause disease on blackberry in the United States.

The article presents the findings of a study on daylily plants infected by a disease known as Armillaria root rot (ARR). Armillaria species are almost always associated with the colonization of wood, and are most often found on trees and shrubs such as fir, oak, pine, rhododendron, lilac and dogwood. Research indicates that it is impossible to completely eradicate Armillaria, although cultural methods, including the removal of infected plants and as much of the diseased root systems and removal of hardwood stumps, could reduce the damage caused by ARR.