Semiochemical-baited traps to monitor the invasive pea leaf weevil, Sitona lineatus L. during two distinct periods of adult activity

The pea leaf weevil Sitona lineatus L., (Coleoptera: Curculionidae) is an invasive pest of field pea and faba bean in North America.  Pea leaf weevils are univoltine, but have two periods of adult activity.  In the spring, overwintered adults migrate to reproductive host plants and form mating aggregations using host plant volatiles and a male-produced pheromone (4-methyl-3,5-heptanedione) as cues (Blight et al 1984; Blight & Wadhams 1987).  In the fall, newly emerged adults migrate to overwintering sites; it is not currently known if semiochemicals are important cues at this time.  Traps baited with these semiochemicals have been used to trap pea leaf weevils during the spring in their native range (Blight & Wadhams 1987; Nielsen & Jensen 1993).  The objective of this research is to optimize a semiochemical-baited trap system to assess pea leaf weevil activity during both the spring and fall and to monitor range expansion of this pest in North America.  In 2014, pitfall traps baited with aggregation pheromone were attractive to pea leaf weevils in both the spring and fall, but host plant volatiles were only important in the fall.  More males than females were trapped in the spring, but in the fall, sex ratios were even.  In 2015, pheromone lures with and without host plant volatiles were tested to determine which combination of semiochemicals better predicts weevil damage. Response of weevils to semiochemicals during the two periods of adult activity was tested under controlled conditions to further investigate plasticity in response to these semiochemicals.