An aggregation pheromone system for monitoring pea leaf weevil (Coleoptera: Curculionidae) in the Pacific Northwest

A 2-year field study was conducted to determine the effectiveness of an agg regation pheromone for monitoring activity of the pea leaf weevil, Sitona l ineatus (L.), in the Pacific Northwest. Relationships between pheromone tra p catches, damage to pea seedlings, and time of plant emergence were examin ed. Traps with and without pheromone lures were set along the edges of fiel ds before planting of peas and were monitored at 5-7 day intervals in the s pring of each year. Seedling damage was estimated by counting the number of feeding notches on seedlings at the 3-node stage of development. Highest m ean trap catches occurred around 25 April in both years. The aggregation ph eromone also attracted alfalfa weevil, Hypera postica (Gyllenhal), but in m uch lower numbers than pea leaf weevil. Number of pea leaf weevil collected in traps was not related directly to seedling damage at a local or regiona l level. Seedling damage was related to the time of plant emergence; plants emerging before 15 May, closer to the time of high flight activity, sustai ned much more damage than plants emerging later. It is concluded that the p ea leaf weevil aggregation pheromone could be used to time more accurately the planting of spring peas to minimize feeding damage and could be an impo rtant component of integrated pest management programs for the insect.