Irrigated Inland Northwest poplars represent a unique agroforestry ecosystem as a short-rotation woody crop on a 15-year rotation.  This multi-use crop is grown in Oregon and Washington under the stringent guidelines of the Forest Stewardship Council (FSC).  The emphasis FSC places on environmental quality and the limitation of evaluating management decisions only after several years puts a premium on understanding the hybrid poplar ecosystem, specifically the insect community. This seven-year project investigated the arboreal and terrestrial insect community through deployment of light, pheromone-baited and pitfall traps and sweep netting.  Knowledge of the insect community and the presence of both pests and beneficials were used to develop natural history studies and techniques to reduce pest damage with minimal environmental impact.  Short- and long-term strategies have been developed within this agroforest ecosystem ranging from the utilization of mating disruption and the harboring of natural enemies to guiding resistant stock selection and planting methodology.  

Results/Conclusions

Surveys have indicated that the insect communities varied with poplar stand age, and that pestiferous and beneficial insects were present in all stands.  Further, these findings suggest that insect diversity is higher in younger (H’=2.44±0.28) than older stands (H’=0.82±0.23).  Natural histories of the common pests, Parathene robiniae (Lepidoptera: Sesiidae), Prionoxystus robiniae (Lepidoptera:  Cossidae), Cryptorhynchus lapathi (Coleoptera: Curculionidae) were investigated and described.  Management techniques were then advanced for major pests that met FSC criteria.  Short-term measures include the testing and implementation of mating disruption for Pa. robiniae and Pr. robiniae and investigating the presence of natural enemies.  Eulophus orgyia (Hymenoptera: Eulophidae) was recently noted in the hybrid poplars and has provided adequate suppression of two pests:  Orthosia hibisci (Lepidoptera: Noctuidae) and Gluphisia septentrionis (Lepidoptera: Notodontidae).  Long-term techniques have been developed with the greater understanding of the local insect community.  These insect surveys have shown links between poplar varieties and the associated pest susceptibility, leading to the planting of more resistant varieties.  Novel planting techniques are being explored in response to the understanding of the natural history of several pests.  We have shown that environmentally friendly protection can be successfully implemented in this agroecosystem.  By utilizing our knowledge of the insect community associated with hybrid poplars, pesticide use within this system has been reduced.  Finally, techniques developed herein could offer protection to ecologically sensitive natural systems from invasive pests such as Lymantria dispar (Lepidoptera: Lymantriidae) and Anoplophora glabripennis (Coleoptera: Cerambycidae).