Tag: field pea

Week 4: Pea Leaf Weevil

The pea leaf weevil is now present in Alberta, Saskatchewan, and Manitoba. Learn more about the biology of the pea leaf weevil here and about its distribution across western Canada here.

An adult pea leaf weevil, Sitona lineatus, feeding along the margin of a field pea plant, leaving behind a ‘u’-shaped feeding notch. Picture by Jon Williams, AAFC.

This insect causes damage to field pea and faba bean crops during the adult stage and during larval development. Adult pea leaf weevil eat the foliage of their host plants, leaving ‘u’-shaped notches along the edge of the leaves.

A field pea plant with pea leaf weevil feeding damage. Picture by Meghan Vankosky, AAFC.

Adult pea leaf weevil will also feed on a variety of other legume and pulse crops, including alfalfa, chickpea, and soybean. Most adult feeding on these hosts takes place in early spring before pea and faba seedlings emerge, and again after peas and fabas have been harvested in summer and early fall.

Faba bean plants with adult pea leaf weevil feeding damage. Picture by Meghan Vankosky, AAFC.

Pea leaf weevil larvae damage the nitrogen-fixing root nodules on field pea and faba bean plants.

A root nodule from a field pea plant with damage caused by pea leaf weevil larvae. Areas with damage appear a dark pink colour. Picture by Meghan Vankosky, AAFC.

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). 

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).