Pea leaf weevils are on the prowl

As crops are beginning to pop up – so is the pea leaf weevil (Sitona lineatus). Adults emerge in the spring and feed on legumes, such as field peas, faba beans, alfalfa, beans and lentils (causing characteristic “notching” or “scalloping” on the edges of leaves) before laying their eggs in field peas and faba beans. Each adult female can lay over 300 eggs in one summer! The eggs hatch in the soil near developing plants and larvae move to feed on nitrogen-fixing nodules. This results in partial or complete inhibition of nitrogen fixation by the plant, causing poor plant growth. Feeding by adults on the foliage and by larvae on the root nodules contributes to yield losses in field pea and faba bean crops.

Adult pea leaf weevil and a ‘u’-shaped notch resulting from feeding by the adult weevil. Photo credit: Jonathon Williams, AAFC-Saskatoon.

The pea leaf weevil is a slender greyish-brown beetle measuring approximately 5 mm in length. These insects can be distinguished by three light-coloured stripes extending length-wise down the thorax and the abdomen.  All species of Sitona, including the pea leaf weevil, have a short or ‘broad’ snout unlike species like the cabbage seedpod weevil that have a long, curved snout. Mature larvae grow up to 3.5-5.5 mm long. The larvae are legless and c-shaped with a brown head. 

An adult pea leaf weevil, missing some scales, but showing the stripes extending onto the pronotum/thorax. Photo credit: Jonathon Williams, AAFC-Saskatoon.

Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta and in the PPMN monitoring protocol.  Also access the Pea leaf weevil page from the Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Management field guide. (en français : Guide d’identification des ravageurs des grandes cultures et des cultures fourragères et de leurs ennemis naturels et mesures de lutte applicables à l’Ouest canadien).