Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 9, 1997
Publication Date: N/A
Interpretive Summary: Control of the silverleaf whitefly using their own natural enemies is hampered because insecticides are often sprayed against other pests in the same crops. The sprays kill the delicate tiny parasitic wasps, each of which normally can destroy about 40 whitefly young a day. The results enabled the identification of which insecticides are harmless and which are most toxic to two beneficial species. One insecticide was relatively harmless to parasites still within the larval whiteflies, and other insecticides could be used if sprays were timed to avoid susceptable stages of the parasite wasp. Some insecticides were toxic to all parasite stages and thus their use should be avoided. The results will allow producers to reduce the total amount of pesticides sprayed on vegetable crops while using natural methods to control whiteflies.
The overall objective of this laboratory study was to determine if parasitoids can be conserved or augmented against Bemisia argentifolii in crops where insecticides are also applied for other pests. Lethal and sublethal effects were measured for six insecticides applied to host larvae containing two different developmental stages each of Eretmocerus mundus Mercet from Spain, and a common local Eretmocerus sp. Survival varied according to insecticide, parasitoid species and developmental stage. When applied five days after parasitoid oviposition, the carbamate thiodicarb allowed a high rate of adult emergence by both species and developmental stage. When applied five days after parasitoid oviposition, the carbamate thiodicarb allowed a high rate of adult emergence by both species, while emergence ranged from 5-34% following applications of the halogenated hydrocarbon endosulfan, the organophosphates azinphos-methyl and methyl parathion, and the insect growth regulator buprofezin. The pyrethroid bifenthrin was most toxic to both parasitoids in both developmental stages. When applied just before expected parasitoid emergence, survival ranged from 47.2 to 92.2% with buprofezin, thiodicarb and endosulfan. There were some differential responses between parasitoid species among some insecticides. Some significant differences among treatments in longevity of emerged adults were detected, but females of both parasitoid species that survived the least toxic materials were able to mate and reproduce.