Friday, 26 May 2017

Weekly Update (May 25, 2017; Wk 04) - Pea leaf weevil

Pea Leaf Weevil (Sitona lineatus– The pea leaf weevil simulation model will be used to monitor weevil development across the prairies. Weekly temperature data collected across the prairies is incorporated into the simulation model which calculates estimates of weevil development stages based on biological parameters for Sitona lineatus.

The PLW model was run for Lethbridge AB and Saskatoon SK. Meteorological data (April 1 – May 15, 2017) and climate data (May 16- June 30) were used to predict PLW phenology.  Output indicates that PLW oviposition in Lethbridge is approximately one week earlier than Saskatoon.  Reminder - Access last week's PLW model output predictions here.

Pea leaf weevils emerge in the spring primarily by flying (at temperatures above 17ºC) or they may walk short distances. Pea leaf weevil movement into peas and faba beans is achieved primarily through flight.  Adults are slender, greyish-brown measuring approximately 5 mm in length (Fig. 1, Left).  

The pea leaf weevil resembles the sweet clover weevil (Sitona cylindricollis) but the former is distinguished by three light-coloured stripes extending length-wise down thorax and sometimes the abdomen.  All species of Sitona, including the pea leaf weevil, have a short snout.  

Figure 3.  Comparison images and descriptions of four Sitona species adults including pea leaf weevil (Left).

Adults will feed upon the leaf margins and growing points of legume seedlings (alfalfa, clover, dry beans, faba beans, peas) and produce a characteristic, scalloped (notched) edge.  Females lay 1000 to 1500 eggs in the soil either near or on developing pea or faba bean plants from May to June.

Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta.  Also refer to the pea leaf weevil page within the "Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide" - both English-enhanced or French-enhanced versions are available.  A review of this insect was published in 2011 in Prairie Soils and Crops by Carcamo and Vankosky.