Castle S. J., Byrne, F. J., Bi, J. L., and Toscano, N. C. Spatial and temporal distribution of imidacloprid and thiamethoxam in citrus and impact on Homalodisca coagulate populations. Pest Manag. Sci.

University of California, Riverside, Riverside, California, United States
Pest Management Science (Impact Factor: 2.74). 01/2005; 61(1):75-84. DOI: 10.1002/ps.949
Source: PubMed

ABSTRACT 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.

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    • "Although resistance has been documented, little is known about how this widespread adoption may have had unanticipated effects on the biology and ecology of pests over time. To date, numerous studies have previously reported declining neonicotinoid concentrations over time in both annual and perennial cropping systems, often focusing on season-long population dynamics of pest species with high reproductive capacity and multiple generations per growing season (Byrne et al. 2005a,b, 2007, 2010; Castle et al. 2005). In cultivated potato, variable concentrations of systemic neonicotinoids in plant tissue after at-plant applications may be one additional factor contributing to the development of Colorado potato beetle resistance (Olson et al. 2004). "
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    ABSTRACT: Emergence phenology and fitness attributes of several Colorado potato beetle, Leptinotarsa decemlineata (Say), populations were measured under field and greenhouse conditions. Anecdotal observations by producers and pest managers in many locations of the upper Midwest increasingly suggested that select populations of Colorado potato beetle were emerging over a longer period in the spring and were less sensitive to systemic neonicotinoids in cultivated potato. These changes in emergence phenology may be related to changes in systemic insecticide concentration over time. Specifically, a prolonged period of adult emergence in the spring increases the potential of low-dose chronic exposure to systemic neonicotinoid insecticides in potato. In 2010 and 2011, our objectives were twofold: 1) establish a common garden experiment to compare the emergence phenology of Colorado potato beetle populations uniquely managed with variable insecticide inputs, and 2) measure postdormancy fitness of emerged adult beetles from among these selected populations. Cumulative adult emergence was modeled with logistic regression. Results from this study found no clear evidence for direct relationships between phenology and management history or resistance. Differences in reproductive capacity, sex ratio, and body size were apparent in some instances. However, these results did not uniformly correspond to one specific form of potato pest management tested here. In this study, long-term reliance on systemic insecticides for Colorado potato beetle control did not serve as a strong predictor for variable life history for selected populations in Wisconsin.
    Journal of Economic Entomology 12/2013; 106(6):2491-505. DOI:10.1603/EC13277 · 1.61 Impact Factor
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    • "The intraplant variability in imidacloprid titers was over 100-fold, but this type of variability has been observed in xylem ßuid after soil applied applications to citrus (Castle et al. 2005) and across leaf ages in sugar beets (Westwood et al. 1998). "
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    ABSTRACT: ELISA techniques were used to detect imidacloprid in guttation fluid of young cantaloupe plants in Arizona. Imidacloprid was detected at up to 4.1 microg/ml (ppm) in a coincidental guttation collection 3 d after a top label rate soil application and at 37 microg/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.
    Journal of Economic Entomology 02/2012; 105(1):67-71. DOI:10.1603/EC11251 · 1.61 Impact Factor
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    • "• Volume 58, Number 4 threat to the wine industry in Southern to Central California (Castle et al. 2005). Indeed, since the first identification of GWSS in the California vineyards, programs aimed at controlling the dissemination of this insect as a strategy to prevent PD outbreaks have involved more than $160 million of direct investments ( phpps/pdcp/). "
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    ABSTRACT: Pests and diseases of plants are cosmopolitan, and have been from the beginning of agriculture. Domestication of plants and breeding for increased yields allowed civilizations to develop, but often created new problems associated with monocultures and displaced native flora and fauna. In the modern era, inorganic fertilizer in some cases has eliminated crop rotation and led to pollution of rivers and aquifers. The following descriptions of several international collaborators’ attempts to manage pests and diseases represent the beginnings of a practical international entomology, and are a form of science diplomacy. A common theme in each of the examples is the urgent need for new tools in pest and disease management.
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