Augmentation Biological Control Using the Entomopathogenic Nematode Steinernema Feltiae against the South American Leafminer Liriomyza Huidobrensis

Routine measures used to control the larval stages of non-statutory leafminer species in the United Kingdom rely largely on either the use of the braconid parasitoid Dacnusa sibirica Telenga and the eulophid wasp Diglyphus isaea Walker as, for example, in tomato crops, or on chemical insecticides for control in leafy salad and ornamental plants (Garthwaite and Thomas, 2001). The availability of effective chemical insecticides for use against leafminers is severely limited, and the introduction of parasitoids alone to control leafminer populations requires repetitive releases of large numbers (Sher et al., 2000), which would be prohibitively expensive. Therefore to reliably achieve eradication a new approach was required. A non-chemical control method using the entomopathogenic nematode Steinernema feltiae (Filipjev) as a foliar treatment against larval instars was developed (Williams and Macdonald, 1994; Williams and Walters, 1995, 2000). However, before nematodes could be integrated into pest management programs, information on their compatibility with chemical insecticides was required. Earlier studies addressed the consequences of direct exposure to solutions of insecticides on the behavior and infectivity of selected entomopathogenic nematode species; however, combinations of insecticides and nematode species available for use in the United Kingdom were not included. Additionally, the effect of dry pesticide residue on subsequent nematode applications had not previously been investigated.