Effects of Pesticides on Diglyphus isaea (Walker) and Dacnusa sibirica Telenga, Parasitoids of Liriomyza trifolii (Burgess)

Abstract

The effects of 28 insecticides, 8 acaricides and 18 fungicides on Diglyphus isaea (Walker) and Dacnusa sibirica Telenga, parasitoids of Liriomyza trifolii (Burgess), were evaluated by laboratory experiments to determine their toxicity to the adults and larvae of these parasitoids, and their action on parasitism. All tested organophosphate, synthetic pyrethroid, nereistoxin analog and carbamate insecticides were harmful to the adults and mature larvae of D. isaea and the adults of D. sibirica, and also prevented their parasitism of larvae of L. trifolii. The period of residual contact toxicity of granules of acephate and fosthiazate applied in soil to adults of D. isaea and D. sibirica was more than 6 weeks. Tested chloronicotinyl insecticides were moderately harmful to the adults of the parasitoids, and imidacloprid prevented parasitism by D. isaea. Granules of imidacloprid applied in soil did not show contact toxicity, and prevention of parasitism by D. isaea was slight. Bromopropylate, dicofol and fenbutatin oxide acaricides were slightly harmful to the adult parasitoids, but fenbutatin oxide was safe to larvae and parasitism by D. isaea. Hexythiazox, Bacillus thuringiensis and sodium oleate were safe for adults and larvae of D. isaea, and parasitism by the two species of parasitoids. Growth regulator insecticides, buprofezin, flufenoxuron, pyriproxyfen and teflubenzuron, were safe for the adults, parasitism by the two species of parasitoids and development of progeny oviposited by adult D. isaea dipped in them. Except pyriproxyfen, these IGR insecticides were safe for larvae of D. isaea. Pymetrozine was safe for adults of the two parasitoids, the larvae of D. isaea and parasitism by D. sibirica, while it was slightly harmful to parasitism by D. isaea. Most tested fungicides were safe. Captan was moderately harmful to adults of the two parasitoids, but was safe for larvae and parasitism by the parasitoids. Thus, it is suggested that IGRs (buprofezin, flufenoxuron, pyriproxyfen and teflubenzuron), Bacillus thuringiensis, sodium oleate, pymetrozine, some acaricides and most fungicides can be combined with D. isaea and D. sibirica in L. trifolii IPM programs.