Combination of insecticides and entomopathogenic nematodes to control Diabrotica virgifera virgifera
Chemical treatments are the most widely used methods to control Diabrotica virgifera virgifera (EPPO A2 quarantine pest). However, it has been shown that some entomopathogenic nematodes (Steinernema carpocapsae, S. feltiae and Heterorhaditis bacteriophora) can reduce numbers of larvae, adult emergence and damage. Laboratory studies have been carried out in USA to determine whether the combined use of insecticides (terbufos, fonofos, tefluthrin) and entomatopathogenic nematodes (S. carpocapsae) could increase insect mortality. Combinations of insecticides and nematodes were tested at several doses and exposure times, and by using different bioassay methods on larvae of D. virgifera virgifera. Results showed that larval mortality with combinations of terbufos or fonofos and S. carpocapsae was increased (additive effect) in some cases. However, an antagonist effect was obtained in a few cases. Combinations of tefluthrin with S. carpocapsae gave in several cases a synergistic response and an average increase of 24 % (lowest increase 12% - highest 44 %) in expected mortality. This synergy was also observed when tefluthrin was used with another nematode species H. bacteriophora. These results obtained in laboratory conditions open new possibilities of integrated management, but need to be confirmed in the field.
Sources
Nishimatsu, T.; Jackson, J.J. (1998) Interaction of insecticides, entomopathogenic nematodes and larvae of the Western corn rootworm (Coleoptera: Chrysomelidae).
Journal of Economic Entomology, 91(2), 410-418.