Pea Leaf Weevils: A pest to watch out for Back »

Figure 1. Notched field pea leaves.
Courtesy: Patrick Beauzay, NDSU Extension


Written collaboratively by Adam Varenhorst, Ruth Beck, Christopher Graham, Patrick Wagner, and Amanda Bachmann.

Pea Leaf Weevils

The pea leaf weevil was introduced into the United States in the 1920’s on both the East and West coast. Although not yet reported in South Dakota, the pea leaf weevil is getting closer. In 2016, researchers at North Dakota State University documented fields that had pea leaf weevil infestations. In 2017, the same researchers at NDSU determined that the area of infestation expanded from Golden Valley County (2016, 2017) to Stark (2017) and Mountrail (2017) Counties. Prior to its discovery in North Dakota, the pea leaf weevil was previously established in Washington, Idaho, and Western Montana. Over the last ten years, the pea leaf weevil range has expanded in relation to the increased amount of acreage planted to field peas.

Damage to Crops
Pea leaf weevils cause economic damage to both field peas and fava beans. The adults may also be found in clover and alfalfa even though the larvae will not develop on these crops. The adult pea leaf weevils cause distinct half-circle notches on the edges of leaves (Figure 1). However, it is the larvae that cause the economic injury to the plant. Larvae of the pea leaf weevil feed on root nodules, which is believed to reduce the plant’s ability to fix nitrogen (Figure 2).


Figure 2. Pea leaf weevil larva feeding on root nodules of a field pea plant. Courtesy: Patrick Beauzay, NDSU Extension
 

Identification

Adults
Adult pea leaf weevils are light brown-gray with a long broad snout. The beetles have a slender body and are slightly less than a quarter of an inch long. Adult pea leaf weevils have parallel black lines on their bodies (Figure 3). These weevils are very similar to others that can be found in alfalfa; however, their presence is most easily identified based on the leaf feeding generally observed on lower leaves.


Figure 3. Pea leaf weevil adult.
Courtesy: Natasha Wright, Cook’s Pest Control, Bugwood.org
 

Larvae
The larvae of pea leaf weevils are small and white with a dark brown head capsule. When disturbed, the larvae will curl up in a C-shape. They are very similar in appearance to grubs, but will be a fraction of the size and legless (Figure 4).


Figure 4. Pea leaf weevil larva.
Courtesy: Patrick Beauzay, NDSU Extension
 

Reporting Infestations

If you believe you have pea leaf weevils feeding in your field, please notify an SDSU Extension entomologist or agronomist. Otherwise, please keep a look out for this pest and notify us should you observe anything in the future.

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