Biological control in an agro-forest of hybrid poplars

Gluphisia septentrionis defoliated several thousand acres of hybrid poplars in June 2009. Normally there are two generations of this pest each year. However, 25% of the larvae of the first generation were parasitized by Eulophus orgyiae and 85% of the eggs of the second generation were parasitized by Trichogramma spp. thus the poplar trees were not defoliated a second time in 2009. Trichogramma populations were detected in early May 2010, attacking eggs of another defoliator the Speckled Green Fruitworm, Orthosia hibisci. Both Trichogramma and E. orgyiae can host switch from attacking O. hibisci in May to attacking the first generation of G. septentrionis in June, thereby allowing a build-up of beneficial insects to attack the second generation of Gluphisia in late August. Other parasitoids (Diptera:Tachinidae) and predators (Hemiptera: Pentatomidae) contribute toward controlling defoliating pests of hybrid poplars in the Pacific Northwest.