FIELD STUDIES ON THE EFFECT OF PESTICIDES ON THE DIAMONDBACK MOTH (LEPIDOPTERA, PLUTELLIDAE) AND PARASITISM BY DIADEGMA-INSULARE (HYMENOPTERA, ICHNEUMONIDAE)
Ab. Idris et E. Grafius, FIELD STUDIES ON THE EFFECT OF PESTICIDES ON THE DIAMONDBACK MOTH (LEPIDOPTERA, PLUTELLIDAE) AND PARASITISM BY DIADEGMA-INSULARE (HYMENOPTERA, ICHNEUMONIDAE), Journal of economic entomology, 86(4), 1993, pp. 1196-1202
The effects of pesticides on the diamondback moth, Plutella xylostella
(L.), and parasitism by Diadegma insulare (Cresson) was studied at th
e Michigan State University Entomology Research Farm during July and A
ugust 1990. The range of diamondback moth parasitism from three differ
ent locations in Michigan was 60.8-83.3%. Pesticides used were Bacillu
s thuringiensis var. Kurstaki (Berliner), thiodicarb, thiodicarb + B.
thuringiensis, chlorpyrifos, permethrin, ICIA 0321 (pyrethroid), and e
sfenvalerate. Diamondback larval moth mortality was not significantly
different among the treated plots but was significantly higher than in
untreated plots 3 d after spraying. The change in number of diamondba
ck moth larvae (0 versus 3 d), and diamondback moth and D. insulare pu
pae (0 versus 6 d) was similar in all treatments. Parasitism by D. ins
ulare in treated plots was not affected 6 d after spraying with any pe
sticide tested. Mean percentage parasitism by D. insulare in guard row
s was also not different. However, the percentage parasitism in cages
3 d after treatment with permethrin, azinphosmethyl, or B. thuringiens
is or untreated was 7.8, 13.3, 81.5, and 79.4%, respectively. Parasiti
sm by D. insulare of the diamondback moth larvae seems to be influence
d by the vegetation or refuge plants present outside the experimental
plots. Diamondback moth parasitism by D. insulare may not be affected
severely if pesticides are judiciously used.