Evaluating host plant preference and pheromone attract and kill as strategies to manage pea leaf weevil Sitona lineatus (L.) (Coleoptera: Curculionidae) in Montana

Abstract

Pea leaf weevil (Sitona lineatus) is the most common insect pest of field peas grown in Montana. Montana is the number one producer of field pea in the US. Currently, Montana producers spray insecticides at least once or twice during the spring growing season to avoid leaf damage inflicted by pea leaf weevil adults and larvae. Complete reliance on insecticides may, however, raise the risk of pea leaf weevil populations developing genetic resistance. Therefore, this project focuses on development of alternative pulse insect pest management strategies such as pheromone-based attract and kill and host plant preference. For the attract and kill strategy 6 different treatments compared combinations of aggregate pheromone (4-methyal-3,5- heptanedione) alone in two different forms; septa and pellet, pheromone with granular insecticide (Deltamethrin). To determine the effect of host variety on adult feeding preference, 10 field pea, 2 faba bean, 2 lentil and 2 chickpea varieties were assessed for feeding damage. Crescent shaped notches were counted on 10 individual plants per replicate plot. The average number of larvae within the nitrogen fixing root nodules of each variety was also recorded on 5 randomly selected individual plants per plot. Faba bean was the most preferred host while lentil and chickpea suffered almost no feeding damage. 'Delta' and 'Lifter' field pea varieties appeared to be preferred over 'DS Admiral' and 'AC Agassiz' varieties. Given the significant level of feeding on all pea and faba bean cultivars further evaluation of low-cost pheromone traps are essential to establishing an IPM control approach.