Adult and larval pea leaf weevil - Photos by: H. Goulet (L)and L. Dosdall (R)

By Dori Modney with files from Alberta Agriculture

Pea leaf weevil – latest Alberta survey and map available

Feb 14, 2022 | 4:08 PM

LETHBRIDGE, AB. — Initial findings from the 2021 pea leaf weevil (PWL) survey maps for Alberta are out and showing lower numbers than what has been seen in previous years. This could be due to the dryer growing conditions, especially in Southern Alberta.

The survey, completed in late May and early June of 2021, was based on damage ratings in 225 fields within 58 municipalities.

In each field, the total number of feeding notches per plant are counted on 10 plants in 5 locations near the field margin. The damage rating for a particular field is the average number of notches per plant.

Although this survey concentrates on damage done by the adult, yield losses are caused by the larval damage to the nitrogen fixing root nodules.

Pea leaf Weevil map – Alberta Agriculture

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Producers should use the information generated from this survey, along with their own experience to plan control strategies such as seed treatment for the 2022 crop year. Research has shown that seed treatment is much more effective in reducing losses from pea leaf weevil than foliar treatments.

The first record of pea leaf weevil attacking field peas in Alberta was in 2000 near Lethbridge. Since then, the PLW’s range has expanded to north of Edmonton (2020). In Alberta, the pest occurs commonly in pea fields south of Highway-1, with density of the insect and resulting damage increasing towards Lethbridge.

Since 2001, crop insect surveyors carry out annual pea leaf weevil surveys that help predict PLW range and levels of damage. Surveyors visit pea fields from Warner in the south to Peace River in the north-west.

Since 2014, significant pea leaf weevil damage has been seen on faba beans in a much larger area than shown in this survey that is conducted on field peas. This insect causes as much or more damage on faba beans. The true economic damage of pea leaf weevil on both peas and faba beans on the higher organic matter soils of central Alberta is not well understood, but research has been initiated to work out these relationships.

More information can be found on the Alberta Agriculture website.