Classical biological control of the cereal leaf beetle, Oulema melanopus (Coleoptera: Chrysomelidae), in Washington State and role of field insectaries, a review

The cereal leaf beetle (CLB) Oulema melanopus (Coleoptera: Chrysomelidae), was considered a high risk to Washington State's cereal grain production when the pest was found there in 1999. Biological control agents, which had proven successful in the Midwest, were introduced beginning in 2000. The parasitoids were released into field insectaries that were modified for the region and set up at CLB hotspots across the state. The egg parasitoid, Anaphes flavipes (Forster) (Hymenoptera: Mymaridae), failed to establish. The larval parasitoid, Tetrastichus julis (Walker) (Hymenoptera: Eulophidae), established successfully at all insectaries. Assays of commercial grain fields showed the parasitoid dispersing widely beyond the insectaries. A proactive Extension programme enabled farmers to benefit from the biocontrol without applying insecticides to manage the CLB. A modified insectary, consisting of oat strips seeded between commercial fields of winter and spring wheat, demonstrated potential as a way for farmers to increase parasitoid populations on their land. Within 5 years of first overwintering, T. julis had established across the state and was effectively suppressing CLB.