Response of two lacewing species to biorational and broad-spectrum insecticides

Green lacewings, including Chrysoperia rufilabris (Burmeister) and Ceraeoch rysa cubana (Hagen), are predators of small, soft-bodied insects including whiteflies. The silverleaf whitefly, Bemisia argentifolii Bellows & Perring [formerly B, tabaci (Gennadius) strain B], is an important pest of agronom ic, vegetable and ornamental crops. Practical use of these lacewings as bio logical control agents would be facilitated by better understanding of thei r responses to both biorational (selective) and broad-spectrum insecticides . The topical and residual toxicity of azadirachtin (Azatin-EC(TM)), insect icidal soap (M-Pede(TM)), paraffinic oil (Sunspray Ultra-Fine Spray Oil(TM) ) and the pyrethroid bifenthrin (Brigade(TM)) to eggs, larvae and adults of the lacewings were studied in the laboratory. Larvae of C. cubana were muc h more tolerant to residues of bifenthrin than was C. rufilabris and were s omewhat more tolerant to topically applied soap. At normal field concentrat ions, azadirachtin (0.005%, by wt a.i.), paraffinic oil (1.0% by volume) an d soap (1.0% by volume) were not toxic to larvae or adults of either specie s either topically or residually. Oil was toxic topically to eggs but azadi rachtin and soap were not. Bifenthrin was toxic topically and residually to larvae and adults but was not so toxic to eggs as was oil. Thus, selectivi ty of all materials tested was relative to lacewing species and lifestage. The relative tolerance to insecticide residues exhibited by C. cubana larva e may be related to its trash-carrying habit, suggesting that use of trash- carrying chrysopids in place of non-trash carriers for augmentative biologi cal control would increase options for non-disruptive chemical intervention when necessary.