Effects of conventional pesticides on the preimaginal developmental stagesand on adults of Trichogramma cordubensis (Hymenoptera : Trichogrammatidae)

The effects of seven pesticides sprayed on hosts with parasitoids at differ ent phases of egg to adult development (24, 24-48, 48-72, 72-96, 120-144, 1 92-216 h) of Trichogramma cordubensis (Vargas & Cabello) were studied. The effect of these pesticides on the mortality of adult parasitoids upon conta ct with the hosts immediately or 24 h after the treatments was also tested. One organophosphate insecticide (trichlorfon), one organochlorine insectic ide (endosulfan), two pyrethroids (deltamethrin and lambda-cyhalothrin), a commercial formulation of Bacillus thuringiensis subsp. Kurstaki, and two f ungicides (acetamide + dithiocarbamete and basic copper sulphate) were sele cted for testing. All the tests were carried out with fresh solutions of co mmercial insecticides applied on host eggs at the recommended concentration . The pesticides applied at different development phases did not affect the duration of parasitoid development, except endosulfan, which delayed the p arasitoid preimaginal development for one day. With few exceptions, the num ber of parasitized host eggs that turned black (i.e. with parasitoid prepup ae) did not differ significantly between the pesticide treatments and the c ontrol. The chemical insecticides affected the adult emergence rates signif icantly, while the other products resulted in emergence rates similar to co ntrol values. The longevity of adult progeny was very short when endosulfan or trichlorfon (< 1 and < 2 days, respectively) were applied. Overall, end osulfan was the pesticide most harmful to the preimaginal development stage s of T. cordubensis. Therefore, the use of this product should be avoided w hen this species is part of an integrated pest control programme.