Pea leaf weevil biology & life cycle
The pea leaf weevil (Sitona lineatus) is an invasive pest that is an increasing threat to pulse production in Western Canada. Adult weevils typically feed on leaf margins and on growing points of seedlings. They create a characteristic notched effect on the leaf edges. The more damaging stage of the life cycle are the larvae which feed on the nodules, restricting or inhibiting nitrogen fixation by the plant.
Under ideal conditions the pea leaf weevil produces one generation per year. The adults overwinter in alfalfa or other perennial legumes. In spring when temperatures rise they either fly or walk to where they want to lay eggs which is typically in the soil near to developing plants. Beginning in mid-May to mid-June they lay between 1000 and 1500 eggs. Once hatched, larvae move to nodules to feed. They go through 5 instars, burrow into the soil and pupate. The new flush of adults emerge in mid-July to August, find pulse crops to feed on and prepare to overwinter.
Spring weather conditions have a significant
effect on the timing and severity of pea leaf
weevil damage.1,2
Temperature: Pea leaf weevils will arrive in fields early if
warm conditions (> 20°C) persist for more
than a few days in late-April or early-May,
which corresponds to higher yield loss.
In years when cool weather persists, the
arrival of pea leaf weevils can be much
later, and the yield impact less serious. Open, warmer winters can also result in higher, more widespread pea leaf weevil populations.
Moisture: Dry years make plants more susceptible
to the pea leaf weevil. In wetter years there
is more nitrogen available to the plant,
making it less susceptible to the pest.
Sources:
1.“Pea Leaf Weevil,” Agri-Facts, Alberta Agriculture, 2014
2.“Pea Leaf Weevil,” Grainews, May 17, 2016
