Cutting failure and damage characterization in Pacific Northwest hybrid poplars

Hybrid poplars in the inland Pacific Northwest are an irrigated woody crop grown to meet today′s fiber demands.  Harvest generally occurs during winter when most pests are dormant.  In spring, growers replant the recently harvested areas with cuttings. Due to the small leaf area, fragile roots and limited reserves, cuttings are vulnerable to common above and below ground pests during this first growing season.  Cuttings represent a long-term investment and it is imperative for the grower to know which pests are causing economic injury and where it is occurring.  Cutting mortality within planting blocks was recorded, characterized and then visualized using Spatial Analysis and Decision Assistance (SADA). This technique allowed for the recognition of species-specific mortality patterns within a planting block. Our findings indicate that even though the location of cutting mortality occurs haphazardly within a block, species-specific mortality patterns are discernable across multiple blocks.  It is our understanding that these patterns are linked to a pest′s mobility, with highly mobile pest showing a broad distribution and sessile pests causing localized pockets of mortality.  Even though our project has brought new light to this system through the identification of the major cutting pests and characterized their damage and mortality patterns, we are unable to predict where these insect-caused mortalities will occur within a newly planted block.  During this project we developed novel control techniques, such as a prophylactic dip to protect cuttings from subterranean pests and propagation techniques.  These techniques include the planting of poles in place of sticks, which dramatically reduces mortality in the first year of planting.