Submitted to: Australian Journal of Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2010
Publication Date: 1/15/2011
Citation: Davies, A.P., Carr, C.M., Scholz, B.G., Zalucki, M.P. 2011. Using Trichogramma Westwood (Hymenoptera: Trichogrammatidae) for insect pest biological control in cotton crops: an Australian perspective. Australian Journal of Entomology. 50:424-440. Interpretive Summary: A USDA-ARS scientist from the Center for Medical, Agricultural, and Veterinary Entomology, Gainesville, Florida, submitted a review paper with colleagues examining the important contribution of Trichogramma egg parasitoids to biological control of insect pests in cotton crops. The review found the role of Trichogramma in cotton pest control has long been understated, and that the parasites have great potential in tropical areas where they seem to thrive. They are especially important for reducing the possible development of resistance to transgenic cotton varieties in susceptible pests as they attack the egg stage. This is because pest eggs that are parasitized do not hatch, and so, never ingest the transgenic cotton, reducing the number of total pests exposed. Conserving natural populations of these parasitoids has proved more effective than mass releases for pest control in cotton, and there is considerable scope to enhance their potential through habitat manipulation, or the provision of companion crops for food and shelter. The aim is to reduce reliance on conventional insecticides for pest control in cotton production and the potential for insect pest resistance development to new technologies.
Technical Abstract: Trichogramma Westwood egg parasitoids alone generally fail to suppress heliothine pests when released in established cotton growing regions. Factors hindering their success include indiscriminate use of detrimental insecticides, compensation for minimal pest larval hatch due to their activity via reduced larval cannibalism or mortality in general, singly laid heliothine eggs avoiding detection, and asynchronous development benefiting host over parasitoid. Yet, despite these limitations, relatively large Trichogramma pretiosum Riley populations pervade and effectively suppress Helicoverpa (Hardwick) pests in Australian Bt (Bacillus thuringiensis Berliner) -transgenic cotton, Gossypium hirsutum L., crops, especially in the Ord River Irrigation Area (ORIA) of tropical northern Australia, where their impact on the potentially resistant pest species, Helicoverpa armigera (Hübner), is considered integral to the local insect resistance management (IRM) strategy for continued, sustainable Bt-transgenic cotton production. When devoid of conventional insecticides, relatively warm and stable conditions of the early dry season in ‘winter’ grown ORIA Bt-transgenic cotton crops are conducive to Trichogramma proliferation and biological control appears effective. Further, there is considerable scope to improve Trichogramma’s biological control potential, in both the ORIA and established cotton growing regions, via habitat manipulation. We propose Trichogramma may prove equally effective in developing agricultural regions of monsoonal northern Australia, and that environmental constraints on Trichogramma survival, and those of other natural enemies, require due consideration prior to their successful application in biological control programmes.