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Title: APPLICATION OF COMPETITIVE ELISA FOR THE QUANTIFICATION OF IMIDACLOPRID TITERS IN XYLEM SAP EXTRACTED FROM GRAPEVINES

Author
item BYRNE, FRANK - U CA, RIVERSIDE
item Castle, Steven
item BI, J - U CA, RIVERSIDE
item TOSCANO, NICK - U CA, RIVERSIDE

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2004
Publication Date: 2/1/2005
Citation: Byrne, F.J., Castle, S.J., Bi, J.L., Toscano, N.C. 2005. Application of competitive elisa for the quantification of imidacloprid titers in xylem sap extracted from grapevines. Journal of Economic Entomology 98(1): 182-187.

Interpretive Summary: Systemic insecticides such as imidacloprid play an important role in insect pest management. Recently, commercial ELISA kits have become available that enable extremely sensitive detection and quantification of residues of certain insecticides in plants. However, it is important to characterize the performance of the commercial kits that are being used in various applications. In the present study, a commercial kit was used to quantify imidacloprid residues in xylem of grapevines. Potential inhibitory effects of grapevine xylem fluid were identified in order to optimize the performance of the kit and provide the most accurate determination of imidacloprid residues. Information on the concentration and persistence of imidacloprid in grapevines is important to growers concerned with managing glassy-winged sharpshooters, vine mealybugs, and other insect pests common to vineyards

Technical Abstract: A competitive ELISA technique was evaluated for quantifying titers of imidacloprid in xylem sap extracted from grapevines that were treated with systemic applications of Admire by chemigation. Although matrix effects were evident with undiluted sap, these could be effectively eliminated by dilution of extracts in water, resulting in a lower sensitivity of the assay of 4 µg.l-1. In a field trial conducted in a commercial vineyard, there was an excellent correlation between Admire application rates and xylem sap concentrations of the active ingredient. At an application rate of 1.17 liters.ha-1 (16 fl. oz. per acre), uptake of imidacloprid into vines was rapid. The insecticide was consistently detected in the xylem for up to 3 months after application at concentrations known to be effective at managing populations of the glassy-winged sharpshooter, Homalodisca coagulata, an important vector of Pierce's Disease in California vineyards. The ELISA is a sensitive technique that can be exploited to study the behavior of systemic insecticides within crop systems and their impact on pest populations.