Toxicity of insecticides to neochrysocharis okazakii, a parasitoid liriomyza leafminers on vegetables

Abstract

Compatible use of biocontrol agents with insecticides is often essential to integrated pest management because the targets of each agent are normally restricted to a single or only a few species of pests and because the agent does not always provide satisfactory pest control. Selective use of chemicals least harmful to biological control agents is then ideal. In the present study, five insecticides, namely imidacloprid, pymetrozine, lufenuron, ethofenprox and clothianidin, were tested to determine their toxicity to Neochrysocharis okazakii (Hymenoptera: Eulophidae), a larval parasitoid of pest Liriomyza leafminers. Individual adult parasitoids were placed in the grass vials whose internal surface was coated with the insecticides. The insecticides tested showed different degrees of toxicity to the parasitoid. The LC50 values were 0.0035, 8.779, 0.0508, 0.0085 and 0.0231mg a.i l-1 for imidacloprid, pymetrozine, lufenuron, ethofenprox and clothianidin, respectively. Based on risk quotient, imidacloprid and enthofenprox are highly toxic. Pymetrozine was harmless to N. okazakii while lufenuron and clothianidin were slightly to moderately to toxic to the parasitoid. Since N. okazakii is an important natural enemy of Liriomyza leafminers, use of imidacloprid or enthofenprox should be avoided. Combination use of augmented N. okazakii with pymetrozine or lufenuron may be counterproductive in a vegetable IPM program.