Behaviour of Pine Sawflies in Relation to Pheromone-Based Pest Management

Abstract: Pine sawflies (Hymenoptera: Diprionidae) are severe pine defoliators. This thesis investigated sawfly behaviour related to the use of pheromones in integrated pest management, including monitoring with pheromone traps and mating disruption. Neodiprion sertiferr females were placed on pine twigs in the field and 11–30 % of the females that remained on their twig after the first mating re-mated. Only 0–2.5 % of the females in a pheromone-treated area mated, whereas 30 % of them mated in the control area. Significantly more females dispersed from the treated area compared with the control. N. sertifer males were studied downwind from pheromone traps and responded to synthetic pheromone from 200 m. They increased their grooming frequency and took off faster than in pheromone-free controls. Sampling range of pheromone traps for N. sertifer was determined, using two different approaches to 400 m and 670 m after 24 hr. The males lived on average 12 days in the field, and the seasonal sampling range was determined to 1040 m. The effective sampling area, that area from which all males originate if the trap catches everything within this area and nothing outside of it, was determined to 4.9 ha. This corresponds to a circular area with a radius of 125 m. Two new concepts describing the origin of insects caught in an attractive trap were defined: cumulative proportional catch (CPC) and catch concentration (CC). CC was obtained by dividing the radius of the effective area with the seasonal sampling range, and thus CC=125/1040 m = 0.12. By using CPC it was estimated that 50 % of the catch originated beyond 450 m from the trap, and the trap is better at reflecting the density of pine sawflies over a larger area (>5 ha) than in smaller stands. During days with no precipitation, wind speed is an important climatic factor for N. sertifer males flying to a pheromone trap.