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Pest management for the glassy-winged sharpshooter, Homalodisca vitripennis Germar (Hemiptera: Cicadellidae), in Kern County, California relies on the application of insecticides. These treatments have contributed to low H. vitripennis field counts since applications were initiated in 2001. However, densities have been high in recent years despite continued management, prompting efforts to evaluate the susceptibility of current populations to insecticides. H. vitripennis adults were subjected to bioassays with five commonly applied insecticides, and the results were compared to baseline toxicities determined in 2002. Two neonicotinoids, imidacloprid and thiamethoxam, were evaluated using systemic uptake bioassays. Contact toxicities of the neonicotinoid acetamiprid and pyrethroids bifenthrin and fenpropathrin were estimated using leaf dip bioassays. Dose-mortality responses were analyzed by probit analysis. For each compound, there was no significant difference in annual LC50 values determined over 2 yr. Compared to baseline toxicities, acetamiprid and bifenthrin were found to be significantly less toxic to H. vitripennis. The LC50 values of these two compounds increased sevenfold and 152-fold, respectively. Tests with the neonicotinoids revealed a trend of decreasing susceptibility levels within each season followed by reversion back to early season LC50 estimates in the following year. In addition, data showed seasonal and site variation in susceptibility to imidacloprid, possibly due to differential applications in nearby fields. [ABSTRACT FROM AUTHOR]

Field-collected nymphs and adults of Bagrada hilaris (Burmeister) (Hemiptera: Penatatomidae) from three locations were evaluated for susceptibility to insecticides representing 10 classes of insecticide chemistry. Although relative susceptibilities differed between leaf-spray and leaf-dip Petri dish bioassays, consistently low LC50 values were determined for chlorpyrifos, bifenthrin, and lambda-cyhalothrin. Fenpropathrin and methomyl had intermediate values. Susceptibility to dinotefuran varied depending on the bioassay, possibly owing to leaf substrates used in the two bioassays. In soil systemic bioassays, the LC50 value of dinotefuran was significantly greater than that of two other neonicotinoids, imidacloprid and thiamethoxam, and the anthranilic diamide, cyantraniliprole. Mortality and feeding damage of B. hilaris and plant growth on insecticide-treated plants in greenhouse trials were consistent with the laboratory bioassays; the best results were seen with bifenthrin, methomyl, and chlorpyrifos. Mortality to the neonicotinoids was not evident; however, feeding damage and plant growth responses on dinotefuran-treated plants damage were similar to the noninfested control. This highlights the apparent antifeedant properties of dinotefuran that may have prevented adults from injuring broccoli plants after exposure to foliar spray residues. Data presented serve as baseline susceptibilities that can be used to monitor for resistance development in field populations of B. hilaris. [ABSTRACT FROM AUTHOR]

BACKGROUND:Bemisia tabaci biotype B is a resistance-pronepest of protected and open agriculture. Systemic uptake bioassays used in resistance monitoring programs have provided important information on susceptibility to neonicotinoid insecticides, but have remained decoupled from field performance. Simultaneous bioassays conducted in field and laboratory settings were compared and related to concentrations of imidacloprid in plant tissue for clearer interpretation of resistance monitoring data. RESULTS: Mean mortalities of adult whiteflies confined on cantaloupe leaves field-treated with three rates of imidacloprid did not exceed 40% in two trials. In contrast, laboratory bioassays conducted on different subsets of the same whitefly populations yielded concentration-response curves suggestive of susceptibility to imidacloprid in five populations (LC50 values from 1.02 to 6.4) relative to a sixth population (LC50 =13.8). In the field, densities of eggs and nymphs were significantly lower on the imidacloprid-treated cantaloupes compared with the untreated control, but the margin of control was greater in 2006 than in 2007. The potential impact of imidacloprid on whitefly eggs was explored in a greenhouse test that showed egg mortality occurring in both early (one-day-old) and late (three-day-old) eggs on cotton leaves systemically treated with imidacloprid. Quantification of imidacloprid residues in cotton leaves used routinely in systemic uptake bioassays revealed concentrations that greatly exceeded concentrations found in the field-treated cantaloupe leaves, at least at the three highest solution concentrations used for uptake. CONCLUSION: Systemic uptake bioassays have been widely used formonitoring B. tabaci resistance to imidacloprid, but without knowledge of imidacloprid concentrations that occur in test leaves relative to field concentrations. Higher mortality observed in systemic uptake bioassays relative to field-treated cantaloupes in this study suggests that field rates of imidacloprid are only partially effective against B. tabaci adults, in contrast to systemic uptake bioassays that showed susceptibility to imidacloprid. The discrepancy between field- and laboratory-based mortalities is probably due to extraordinarily high concentrations of imidacloprid that can occur in leaves of systemic uptake bioassays, potentially skewing perception of susceptibility to imidacloprid. Published 2013. This article is a U.S. Government work and is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

Between 2006 and 2008, 20 populations ofPlanococcusficus (Signoret), from Coachella and San Joaquin Valleys of California were measured in the laboratory for susceptibility to buprofezin, chlorpyrifos, dimethoate, methomyl, and imidacloprid. Toxicity was assessed using a petri dish bioassay technique for contact insecticides and by a systemic uptake technique for imidacloprid. Mixed life stages were tested for susceptibility to all insecticides except for buprofezin, which was measured against early and late instars (first, second, and third). Dose-response regression lines from the mortality data established LC50 and LC99 values by both techniques. Responses of populations from the two geographical locations to all five insecticides varied, in some cases significantly. Variations in susceptibility to each insecticide among sample sites showed a sevenfold difference for buprofezin, 11-old to chlorpyrifos, ninefold to dimethoate, 24-fold to methomyl, and 8.5-fold to imidacloprid. In spite of susceptibility differences between populations, baseline toxicity data revealed that all five insecticides were quite effective based on low LC50s. Chlorpyrifos was the most toxic compound to Planococcusficus populations as shown by lowest LC50Buprofezin was toxic to all immature stages but was more potent to first instars. The highest LC99 estimated by probit analysis of the bioassay data of all 20 populations for each compound was selected as a candidate discriminating dose for use in future resistance monitoring efforts. Establishment of baseline data and development of resistance monitoring tools such as bioassay methods and discriminating doses are essential elements of a sustainable management program for Planococcus riots. [ABSTRACT FROM AUTHOR]

ELISA techniques were used to detect imidacloprid in guttation fluid of young cantaloupe plants in Arizona. Imidacloprid was detected at up to 4.1 µg/ml (ppm) in a coincidental guttation collection 3 d after a top label rate soil application and at 37 µg/ml one d after a separate top label rate soil application study. These imidacloprid titers exceed reported median oral toxicities for several insect species by factors of 10 or more. Pesticides in guttation fluid are a relatively unexplored route of exposure for both pest and beneficial insects, and could represent an important risk for both of these groups in guttation-prone environments. [ABSTRACT FROM AUTHOR]

Two systemic neonicotinoids, imidacloprid and thiamethoxam, are widely used for residual control of several insect pests in cotton (Gossypium spp. ),vegetables, and citrus (Citrus spp.). We evaluated their impact on six species of beneficial arthropods, including four parasitoid species—Aphytis melinus Debach, Gonatocerus ashmeadi Girault, Eretmocerus eremicus Rose & Zolnerowich, and Encarsia formosa Gahan—and two generalist predators—Geocoris punctipes (Say) and Onus insidiosus (Say)—in the laboratory by using a systemic uptake bioassay. Exposure to systemically treated leaves of both neonicotinoids had negative effects on adult survival in all four parasitoids, with higher potency against A. nwlinus as indicated by a low LC50. Mortality was also high for C. ashmeadi, E. eremicus, and E. formosa after exposure to both compounds but only after 48 h posttreatment. The two predators C. punctipes and O. insidiosus were variably susceptible to imidacloprid and thiamethoxam after 96-h exposure. However, toxicity to these predators may be related to their feeding on foliage and not just contact with surface residues. Our laboratory results contradict suggestions of little impact of these systemic neonicotinoids on parasitoids or predators but field studies will be needed to better quantify the levels of such impacts under natural conditions. [ABSTRACT FROM AUTHOR]

Abstract: The glassy-winged sharpshooter, Homalodisca vitripennis (Germar), is a serious pest of grapes and other crop and ornamental plants mainly through its role as a vector of the bacterium Xylella fastidiosa Wells. Citrus harbors large populations of this insect throughout much of the year in areas where the pest is problematic and improved understanding of the population dynamics and management of H. vitripennis on citrus may be key to its management in the broader agricultural landscape. In turn, the study of population dynamics and the development of management strategies require effective and efficient sampling methods. Within-tree sampling distribution studies revealed that adults and nymphs were more abundant and less variable in the upper strata of citrus trees (>1.5 m). They occurred in greater numbers on the southern quadrants of trees but relative variability did not differ due to cardinal direction. We developed and validated several fixed-precision sequential sampling plans for estimating the density of nymphs and adults of H. vitripennis using a pole bucket sampling method. Based on validation from resampling of independent data sets, Green’s sequential sampling model, based on the Taylor’s power law, provided the best overall performance in terms of providing mean density estimates with levels of precision equal to or better than the desired precision over a range of possible insect densities. Average sampling costs varied from about 21 to 189 min for a desired precision of 0.25 depending on insect density and whether the goal is to sample nymphs, adults or both stages combined. Further, the sampling plans developed on orange trees were robust, being equally effective on orange and lemon trees and on trees treated or not with insecticides. [Copyright &y& Elsevier]

A study on the compatibility of the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin (Ascomycota: Hypocreales) with neem was conducted against sweetpotato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), on eggplant. Initially, three concentrations of B. bassiana (106, 107, and 108 conidia ml−1) and three concentrations of neem (0.25, 0.5, and 1.0%) were used as individual treatments against B. tabaci. The highest concentration of B. bassiana yielded the highest B. tabaci egg (25.2%) and nymph mortalities (73.0%), but this was not significantly different from the mortalities caused by the 107 conidia ml−1 suspension. Similarly, the highest concentration of neem yielded the highest egg (27.3%) and nymph mortalities (75.5%), which was also not significantly different from the 0.5% suspension. Therefore, 0.5% neem was used along with 107 B. bassiana conidia ml−1 suspension as an integrated pest management program against B. tabaci. The combination of B. bassiana and neem yielded the highest B. tabaci egg (29.5%) and nymph mortalities (97.2%), and the lowest LT50 (2.08 day) value. Moreover, an integrated combination of B. bassiana with neem caused 27.6 and 20.5% more nymphal mortality than individual treatments of B. bassiana and neem, respectively, 7 days post-application. Thus, a combined application of an entomopathogenic fungus and a botanical insecticide may benefit from both, and it has proven effective for the control of B. tabaci on eggplant. [ABSTRACT FROM AUTHOR]

Integrated pest management (IPM) has the goal of combining several control methods that reduce populations of pest insects and their damage to tolerable levels and thereby reduce the use of costly pesticides that may harm the environment. Insect populations can be monitored during the season to determine when the densities exceed an economic threshold that requires treatment, often as an insecticide application. We developed a simulation model where insect populations varied in exponential growth in fields and dispersed to adjacent fields each day of a season. The first model monitored populations of individual fields in a grid of fields and treated any field with insecticide if it exceeded a threshold population (asynchronous model) as done in traditional IPM. The second model treated the entire grid of fields with insecticide when the average population of all fields exceeded the threshold (synchronous model). We found that the synchronous model at all growth and dispersal rates tested had average field populations during a season that were significantly lower and required fewer treatments than the asynchronous method. Parameters such as percentage of fallow fields, number of fields, and treatment threshold had little affect on relative differences between the two models. The simulations indicate that cooperation among growers in areawide monitoring of fields to obtain an average population estimate for use in treatment thresholds would result in significantly less insect damage and fewer insecticide treatments. The synchronous method is more efficient because population refugia are precluded from which dispersal could reintroduce insects. [ABSTRACT FROM AUTHOR]

Titers of two systemic neonicotinoid insecticides in citrus trees were measured in conjunction with conventional evaluations of their impact on glassy-winged sharpshooter (Homalodisca coagulata (Say); GWSS) populations. Xylem fluid samples were collected at regular intervals and from multiple locations within field-grown citrus trees to determine imidacloprid and thiamethoxam concentrations using commercial ELISA kits. Uptake profiles varied considerably with peak mean titers of imidacloprid occurring 6-8 weeks after application compared with 2 weeks for thiamethoxam. The persistence of each compound also varied as near-peak levels of imidacloprid were sustained for another 6-10 weeks before gradually declining. In contrast, thiamethoxam titers declined more rapidly after the initial peak, possibly reflecting an application rate only one-quarter of that used for imidacloprid. Within-tree distributions were more similar for the two compounds, with no significant effect due to height of the sample (upper or lower half) or to the quadrant location within the tree, with the exception of one quadrant in the thiamethoxam-treated trees. Substantial reductions in GWSS nymphs and adults were observed in imidacloprid-treated trees during the 2001 trial and were sustained for 4-5 months after treatment. Treatment effects on nymphs were not as well pronounced in the 2002 trial, when overall GWSS infestations were much reduced from the previous year. However, consistently lower adult infestations were still observed in 2002 for both treatments compared with untreated trees. Information on the spatial and temporal profiles in citrus trees was obtained for both compounds to complement field impact data and improve understanding of their pest management potential. [ABSTRACT FROM AUTHOR]

Examines the inter-regional differences in baseline toxicity of Bemisia argentifolii Bellows & Perring populations in California and Arizona. Materials and methods; Results of the study; Discussion of findings.

Cotton whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is one of the most important insect pests worldwide. It is known as a species complex consisting of at least 40 cryptic species. Although there are substantial data regarding species composition, parasitoids and endosymbionts of B. tabaci , data on relationship between the pest, parasitoids and endosymbionts are very restricted. Therefore, in this study, secondary endosymbionts in populations of B. tabaci and their parasitoids collected from Turkey and the USA were determined by PCR-based DNA analysis. Whitefly populations in Turkey represented both Mediterranean (MED) and Middle East-Asia Minor1 (MEAM1) genotypes from single or mixed populations of both genotypes. Arsenophonus, Rickettsia and Wolbachia were found in MED, while Hamiltonella and Rickettsia in MEAM1. Whitefly populations collected from Arizona were all MEAM1 and dually infected with Hamiltonella and Rickettsia. The aphelinid parasitoids Encarsia lutea and Eretmocerus mundus predominated in all Turkish populations. While almost all En. lutea populations were infected with Wolbachia, no endosymbionts were detected in any Er. mundus. Parasitoid species and the pattern of secondary endosymbiont infection in Arizona populations were different with Rickettsia detected only from Encarsia sophia while both Rickettsia and Wolbachia were found in Eretmocerus species. As a result, four secondary endosymbionts, namely, Rickettsia, Hamiltonella, Arsenophonus and Wolbachia, were detected from B.tabaci and its parasitoids. Among them only Wolbachia and Rickettsia were found in both the pest and parasitoids. It is conclude that further studies should be pursued to determine effect of these endosymbionts on biology of the parasitoids and success in biological control of B. tabaci. • MED and MEAM1 contains a specific endosymbiont combination. • Wolbachia and Rickettsia were found in both the pest and parasitoids. • En carsia lutea populations served as hosts to Wolbachia. • Parasitoid species and endosymbiont compositions are different in Turkey and Arizona. [ABSTRACT FROM AUTHOR]

Abstract: The effect of dietary supplements on the longevity of male and female Gonatocerus ashmeadi, G. triguttatus and G. fasciatus (Hymenoptera: Mymaridae), was determined in the laboratory. Treatments included: water only, 3:1 honey–water solution, floral and extra-floral nectars from five different plants (excised stems from Fagopyrum esculentum, Lobularia maritima, Phacelia tanacetifolia, Anethum graveolens and Vicia faba), honeydew from Coccus hesperidum and Homalodisca vitripennis (formally H. coagulata), a commercially available food supplement (Eliminade) and citrus foliage. Additionally, the sugar composition of each food resource was determined using HPLC and whole flower extracts. Honey–water and F. esculentum nectar significantly increased longevity of male and female G. ashmeadi, G. triguttatus, and G. fasciatus up to 1860%, 1323% and 1459%, respectively, when compared with water. For both sexes and all three parasitoid species, survival on citrus foliage, H. vitripennis excrement, and P. tanacetifolia flowers was equivalent to that on water only. The longevity of G. ashmeadi and G. triguttatus was up to 539% higher on Eliminade compared with water only, however there was no significant effect of Eliminade on survival of G. fasciatus. Coccus hesperidum honeydew increased survival times up to 665% for all mymarid species compared with citrus foliage alone. HPLC analysis indicated that food resources most beneficial to Gonatocerus parasitoids possessed a high proportion of glucose (up to 44%) and fructose (up to 53%), suggesting that sucrose may not be as important for parasitoid survival. Citrus and P. tanacetifolia flowers contained favorable proportions of glucose and fructose, but the inability of Gonatocerus spp. to benefit from this may be related to flower morphology which could prevent access to nectar. [Copyright &y& Elsevier]