Short communication. Toxicity of abamectin, acetamiprid, imidacloprid, mineral oil and an industrial detergent with respect to Encarsia formosa (Gahan) parasitizing Trialeurodes vaporariorum Westwood nymphs

Abstract

The control of Trialeurodes vaporariorum on tomato with Encarsia formosa is influenced by the use of insecticides. Nine days after allowing E. formosa adults to lay their eggs in T. vaporariorum nymphs on tomato plants, insecticide solutions (abamectin, mineral oil, acetamiprid, an industrial detergent and imadacloprid) were applied at the highest recommended dosages to tomato leaflets in Petri dishes using a Potter tower (four replicates, each involving 20 parasitized nymphs). Adult parasitoids began to emerge on day 7 post-application; this lasted 3-4 days, peaking on day 9 post-application. All the tested products killed the E. formosa pupae (an effect significantly different (P= 0.05) to that achieved with the water control). The products with the greatest toxicity were the detergent (62.99% mortality) and mineral oil (49.55% mortality; no significant difference). The effect of abamectin, the third most toxic agent (33.05% mortality), was not statistically different to that of the mineral oil. Imidacloprid (20.17% mortality) and acetamiprid (20.71% mortality) were the least toxic treatments and could be used (along with abamectin to a lesser extent) in integrated whitefly management programmes involving E. formosa pupae. At the concentrations used, the mineral oil and industrial detergent are not recommended for use in such programmes given their high toxicity to E. formosa pupae.