Quantification of imidacloprid toxicity to avocado thrips, Scirtothrips perseae Nakahara (Thysanoptera: Thripidae), using a combined bioassay and ELISA approach.
A competitive ELISA (enzyme-linked immunosorbent assay) technique was evaluated for quantifying titres of imidacloprid in homogenates of leaf discs sampled from avocado plants treated with systemic applications of imidacloprid 240 g litre(-1) SC (Admire). Matrix effects were evident with undiluted leaf tissue homogenates, but these were effectively eliminated by dilution of homogenates in water. In a field trial conducted in a commercial nursery, there was an excellent correlation between imidacloprid residues within leaves and avocado thrips (Scirtothrips perseae Nakahara) mortality. However, with subsequent sampling over a 2-month period, the relationship between mortality and apparent imidacloprid concentration became less robust, suggesting that the material was being degraded within the plant to non-toxic metabolites. Nevertheless, assessments of thrips mortality on leaves that had been recently treated with imidacloprid established a lower threshold of activity for imidacloprid residues of 6 ng cm(-2) leaf. Limitations on the use of ELISA to quantify the impact of systemic insecticides on pest populations are discussed.
Byrne
Frank J
FJ
Department of Entomology, University of California, Riverside, CA 92521, USA. Frank.byrne@ucr.edu
Toscano
Nick C
NC
Urena
Anthony A
AA
Morse
Joseph G
JG
D000818:Animals; D001681:Biological Assay / Q000379:methods; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D007093:Imidazoles / Q000378:metabolism; D007313:Insecta; D007306:Insecticides / Q000378:metabolism; D000073943:Neonicotinoids; D009574:Nitro Compounds; D027421:Persea / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism
D007093:Imidazoles; D007306:Insecticides; D000073943:Neonicotinoids; D009574:Nitro Compounds; C082359:imidacloprid