Monday, December 11, 2006

Single-species vs. multiple-species natural enemy field release for alfalfa snout beetle, Otiorhynchus ligustici L. (Coleoptera: Curculionidae), biological control using entomopathogenic nematodes

Gabor Neumann, and Elson J. Shields, Cornell University, Entomology, 4142 Comstock Hall, Ithaca, NY

Single- vs. multi-species natural enemy approach in biological control was studied in the alfalfa snout beetle, Otiorhynchus ligustici L., in alfalfa system using entomopathogenic nematodes with different dispersal and foraging behaviors. Steinernema carpocapsae Weiser, strain NY001 (ambusher nematode), Heterorhabditis bacteriophora Poinar, Oswego strain (cruiser nematode) and S. feltiae Filipjev, strain Valko (intermediate nematode) were applied in single-species, two-species combinations, and one three-species combination treatments at 2.5 billion infective juveniles per hectare. All nematodes persisted for a full year (357 days). S. carpocapsae NY001 alone protected the plants from root feeding damage early in the season but allowed for higher alfalfa snout beetle larval survival than all other nematode treatments. H. bacteriophora Oswego allowed for root damage not significantly different from control plots but controlled alfalfa snout beetle larvae late in the season better than S. carpocapsae NY001. S. feltiae Valko protected the plants and controlled host larvae. Evidence was found for better biological control and plant protection when using a nematode combination instead of a single species: S. carpocapsae NY001 and H. bacteriophora Oswego applied together protected the plants better than when H. bacteriophora Oswego acted alone and also allowed for lower host larvae survival than when S. carpocapsae NY001 acted alone. The combination S. feltiae Valko and H. bacteriophora Oswego showed very promising results although the performance of this combination could not be statistically separated from the performance of S. feltiae Valko applied alone.

Species 1: Coleoptera Curculionidae Otiorhynchus ligustici (alfalfa snout beetle)
Species 2: Rhabditida Heterorhabditidae Heterorhabditis
Species 3: Rhabditida Steinernematidae Steinernema