Evaluation of foliar-applied insecticides on abundance of parasitoids of Bemisia argentifolii (Homoptera : Aleyroclidae) in vegetables

The relative abundance of parasitoids of Bemisia argentifolii Bellows & Per ring was studied in insecticide-treated and untreated field plots of cantal oupe, collard, cucumber, and tomato. Treatments were made using foliar-appl ied chlorpyrifos (Lorsban(R), DowElanco, Indianapolis, IN) in 1994, and fol iar-applied imidacloprid (Provado(R), Bayer Corporation, Kansas City, MO) i n 1995 and 1996. Yellow sticky cards were used to monitor parasitoids assoc iated with B. argentifolii in plots untreated or treated weekly in 1994 and bi-weekly in 1995 and 1996 with insecticide over 10 wks. The abundance of parasitoids varied among fields and across years. Five species of parasitoi ds were captured: Eretmocerus sp., Encarsia nigricephala Dozier, E. pergand iella Howard, E. quaintancei Howard, and E. strenua (Silvestri). The first three species comprised approximately 95% of the captured parasitoids. Para sitoids persisted in all field locations and crops whether the vegetables w ere treated or not. Parasitoids were captured in the treated plots througho ut the study, although in fewer numbers than in the untreated plots. Overal l, about 60 to 70% of parasitoids captured were from plots without insectic ide. Whitefly captures on the sticky traps were relatively high in collard compared with the other crops studied. In addition, more E. nigricephala an d E. pergandiella were collected in collard than in the other vegetable cro ps.