Pea leaf weevil – Survey and maps

Overview
Survey and maps

This is not a forecast. It is a summary of the pea leaf weevil situation in Alberta in spring 2023.

Methodology

The annual pea leaf weevil (Sitona lineatus L.) survey was completed in late May and early June 2023. It is based on damage ratings in 215 fields from 56 municipalities.

In each field, the total number of feeding notches per plant are counted on 10 plants in 5 locations near the field edge for a total of 50 plants. 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.

Survey findings

2023 Pea Leaf Weevil Survey Map

The highest damage ratings were found from Sedgewick to Athabasca and east to the Saskatchewan border. We do know that pea leaf weevil is in the Peace region, but the 2023 survey could find very little feeding damage in any of the fields surveyed.

This survey has been done in the Peace region of the province since 2017. In 2022, for the first time, surveyors reported fields with damage levels of an average of 3 to 9 notches per plant. These fields were on the eastern edge of the region. In 2023, surveyors will return to the area these fields were found in to survey and to try to collect weevils.

There were a few hot spots in southern Alberta, but nothing like we have seen in previous years.

Producers should use the information generated from this survey, along with their own experience to plan control strategies such as seed treatment for the 2024 crop year. Research has shown that seed treatment is much more effective in reducing losses from pea leaf weevil than foliar treatments.

Spring weather conditions

Spring weather conditions have a very large impact on the timing and severity of pea leaf weevil damage. When warm conditions (greater than 20 °C) persist for more than a few days in late April or early May, the weevils arrive in fields early. Early arrival corresponds to the potential for higher yield losses. In years where cool weather persists, PLW’s arrival can be much later and the resulting yield impact is lower especially when the crop advances past the six-node stage before weevils arrive. In every case, control decisions should be made on a field-by-field basis.

Find out more about the pea leaf weevil life cycle.

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..

Acknowledgements

Thank you to Adriana Van Tryp and Lee Stellar for your contribution to the survey. This survey was completed by Agriculture and Irrigation, Plant and Bee Health Surveillance Section. Thank you to Jon Williams, AAFC-Saskatoon for the building of this map.

Survey maps

Resources

Pea leaf weevil – Overview

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