Biological Control of Insect Pests on Greenhouse Marigolds

Abstract

In four trials conducted in 1986 and 1987, inundative releases of the parasitic wasp Diglyphus begini (Ashmead) reduced Liriomyza trifolii (Burgess) populations in greenhouse marigolds grown for seed to approximately zero within 8 wk of the first release, and they remained at that level for the duration of the crop. The parasitoid populations within the greenhouses were a direct result of the releases and subsequent reproduction and not because of migration. Releases of Encarsia formosa Gahan and Chrysoperla carnea Stephens may have been responsible for the maintenance of Trialeurodes vaporariorum Westwood, Aphis gossypii Glover, and Myzus persicae Sulzer at acceptable levels in three of four trials. Spot applications of Bacillus thuringiensis successfully controlled Lepidoptera species. Under successful biological control conditions, the upper foliage of the plants at the end of the trials sustained leafminer damage of 0–1.2 mines per leaf.