Effect of pesticides on parasitoid complex of serpentine leafminer Liriomyza trifolii (BURGESS) in Shizuoka Prefecture

Liriomyza trifolii and its hymenopterous parasitoids emerging from collected leaves of vegetables and ornamental crops in Shizuoka Prefecture, Japan, were examined. The parasitoid complex was abundant both in open fields and greenhouses. However, few or no parasitoids emerged from crops treated with some pesticides some time before the survey. The parasitoid complex was composed of 16 species: three braconids, nine eulophids, two pteromalids, one eucoilid and one aphelinid. Four eulophid species, Hemiptarsenus varicornis, Chrysocharis pentheus, Neochrysocaris okazakii and N. formosa, were predominant. H. varicornis seemed to be the most important parasitoid species in greenhouses. In a greenhouse, applications of the selective pesticides, buprofezin, pyridaben, dicofol, fenyroximate, fenbutatin oxide and flufenoxuron, conserved the parasitoid complex and the leafminer population was suppressed subsequently. Applications of the nonselective pesticides, permethrin, methomyl, ethophenprox and prothiofos, destroyed the parasitoid complex and an outbreak of the leafminer followed. One month or more was needed for recovery of high parasitism by the parasitoids after application of nonselective pesticides.