Thursday, 2 June 2016

Weekly Update (June 1, 2016; Wk 05) - Pea leaf weevil

Pea leaf weevil (Sitona lineatus) - Be aware that higher densities of pea leaf weevil and higher levels of feeding damage have been observed in 2016 compared to 2015.  The 2015 pea leaf weevil risk map, based on damage observed on peas, is below as reference.

Review the updates provided by Carcamo for southern Alberta and Hartley related to southwest Saskatchewan posted last week.  

Reminder - 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 (Figure 1).
Figure 1. The pea leaf weevil, Sitona lineatus, measures ~5mm long (Photo: H. Goulet).

The pea leaf weevil resembles the sweet clover weevil (Sitona cylindricollis) yet the former is distinguished by three light-coloured stripes extending length-wise down thorax and sometimes the abdomen (Link here for the Pea leaf weevil monitoring protocol with photos of related weevils).  All species of Sitona, including the pea leaf weevil, have a short snout. 

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 (Figure 2).  Females lay 1000 to 1500 eggs in the soil either near or on developing pea or faba bean plants from May to June.

Figure 2. Feeding notches on clam leaf of pea plant resulting from pea leaf weevil (Photo: L. Dosdall).