Evaluation of Semiochemical-Baited Traps for Monitoring the Pea Leaf Weevil, Sitona lineatus (Coleoptera: Curculionidae) in Field Pea Crops

The pea leaf weevil (PLW), Sitona lineatus L., is a pest of field pea (Pisum sativum L.) and faba bean (Vicia faba L.) that recently invaded the Canadian Prairie Provinces. Although most damage is done by larvae that feed on root nodules, adults are easier to monitor than larvae. Both male and female weevils respond to a male-produced aggregation pheromone and to volatiles released by host plants. The current study tests the attractiveness of synthetic aggregation pheromone, 4-methyl-3,5-heptanedione, and host plant volatiles linalool, (Z)-3-hexenol, and (Z)-3-hexenyl acetate to PLWs in spring when weevils are reproductively active and in fall when weevils seek overwintering sites. Different combinations of semiochemical lures at various doses, released from a variety of devices were tested in pitfall traps. Semiochemical-baited traps captured both male and female weevils in both seasons but the sex ratio varied with season. Weevils did not respond in a dose-dependent manner to pheromone, as all pheromone lures were equally attractive. Pheromone release rate was determined by the release device and not the pheromone dose in the lure. The addition of plant volatiles sometimes increased weevil captures but plant volatiles alone were not attractive to PLW adults. An additional study tested the effect of trap type on weevil capture. Of the 12 different trap types tested, pheromone-baited pitfall traps were most successful in attracting and retaining weevils. Bycatch of other Sitona species was limited to a few specimens of the sweet clover weevil, Sitona cylindricollis Fahraeus.