Relative Susceptibility of Citrus Thrips Nymphs and Adults to Insecticides

Agri-Mek, Assail, Baythroid, Carzol, and Success were all evaluated for their activity towards citrus thrips nymphs relative to adults. Based on leaf dip bioassays, Dimethoate was approximately 3 times more toxic to the adults than to the nymphs. However with leaf dip bioassays, a 3-fold difference, although statistically significant, is usually inconsequential. Success was the only insecticide that demonstrated a noteworthy difference in toxicity to nymphs compared to adults in the bioassay; it was 45 times more toxic to the nymphs than to the adults. Based on X2 contingency tables, lemon trees treated with Carzol, Success, or Baythroid all had significantly lower percentages of nymphs relative to the untreated control. Based on these data, when the citrus thrips population is composed primarily of nymphs, citrus growers and pest control advisors might consider using Carzol, Success, or Baythroid since they appear to impact the nymph population more than the adult population.Arizona Citrus Research Counci