Field pea producers should be on the lookout for a new pest. The pea leaf weevil, a serious pest of pea and other legumes in the United States and Europe, has been found in Southern Alberta this year and authorities are trying to determine the extent of the infestation.
The weevil was discovered last spring when Alberta provincial crop specialist Rob Dunn and entomologists Bob Byers and Kevin Floate at the Lethbridge Research Centre responded to reports of pea seedling damage. Weevils found feeding on pea seedlings were collected and identified as the pea leaf weevil (Sitona lineatus) by weevil expert Don Bright of Agriculture and Agri-Food Canada in Ottawa.
Although the pea leaf weevil likely has only recently come into Alberta, we don't know how long it has been in the province, says Floate. "In previous years when producers had problems with weevils in their pea crops, they may have thought it was just sweet clover weevil because the two weevils look similar and cause the same type of damage in the same crops. If producers don't know what to look for, it would be easy to make that mistake."
The adult pea leaf weevil emerges from overwintering sites in the spring and chews notches in the leaves of legume seedlings including peas, beans, sweet peas, alfalfa and clover. Seedlings are very susceptible to injury and may be killed if the growing tip is damaged. Damage may also occur later in the season by larvae feeding on the roots of plants, particularly on root nodules. However, older plants - six or more expanded leaves with growing tips intact - are much less likely to suffer significant injury.
Adult weevils are slender, grayish brown, about 5 mm in length, and have a short beak. Larvae are light milky white in color with a dark brown head, are legless, cylindrical, soft and fleshy. Pea leaf weevils reproduce only once per year.
Detection can be difficult because the pea leaf weevil looks very similar to the sweet clover weevil, says Floate. Sweet clover weevil may appear at the same time and be mistaken for the pea leaf weevil. One difference, he says, is that the pea leaf weevil has three light-colored, inconspicuous stripes that extend lengthwise down the thorax and often onto the wing covers. Sweet clover weevils do not have these stripes.
Information from the United States suggests that economic damage can occur at densities as low as 3 adult weevils per 10 seedling plants, says Floate, depending upon environmental conditions.
Currently, there are no insecticides registered for control of the pea leaf weevil.
To report pea leaf weevils, or for more information about the pest, producers should contact Alberta Agriculture, Food and Rural Development entomologist Mike Clawson, (403) 381-5237; email, michael.clawson@gov.ab.ca or Dr. Kevin Floate at the Lethbridge Research Centre, (403) 327-4561.
|
