Laboratory bioassays were performed to evaluate the susceptibility of four species of trichogrammatid egg
parasitoids to the toxicity of five bio-rational insecticides used widely to control tomato leaf miner, (TLM) Tuta
absoluta (Lepidoptera: Gelechiidae). The selected parasitoids were Trichogramma evanescens (West.), T. cacoeciae
(Brun), T. pretiosum (Riley), and Trichogrammatoidea bactrae (Nagaraja). Insecticides tested were coragen 20% SC,
dipel2× 6.4%, match 50% EC, proclaim 5% EC and spintor 24% SC. Susceptibility of parasitoids to field rate of the
tested insecticides were evaluated using three bioassay tests: 1) exposing parasitoid females to TLM eggs treated preexposure,
2) exposing parasitoid females to TLM eggs treated post-exposure, and 3) exposing parasitoid females to dry
insecticide residue on filter paper. Results revealed that the tested insecticides showed various degree of adverse impact
on all tested parasitoid species, including reduction in rates of parasitism and adult emergence when exposing
parasitoids adults to host eggs treated pre or post exposure. Spintor and proclaim were the most toxic to tested
parasitoids, while dipel 2× and match were slightly toxic. T. bactrae was the most tolerant parasitoid species, while T.
pretiosum was the most susceptible one. Data of exposing parasitoid adults to insecticide residues indicated that
proclaim had the highest toxicity against T. pretiosum at 92.5% adults' mortality, followed by spintor against the same
species at 85%. T. evanescens was more susceptible to coragen and spintor at 70 and 62.5% mortality, respectively.
Meanwhile, match caused moderate toxicity, as the mortality ranged from 17.50% in T. evanescens to 37.50% in T.
pretiosum.