Cabbage Seedpod Weevil Management in Canola

Cabbage Seedpod Weevil Management in Canola

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Dale Whaley, Douglas County Extension, Washington State University, Frank Young, Crop and Soil Sciences, Washington State University, Karen Sowers, Crop and Soil Sciences, Washington State University, Dennis Roe, Crop and Soil Sciences, Washington State University
As winter canola acreage increases in Washington State, the cabbage seedpod weevil is becoming a problem. In addition to canola, this tiny weevil can also feed on flixweed, tansy mustard, and whitetop. If left unmanaged, the pest can damage ripening canola seeds enough to impact overall yields by as much as 50%. This publication describes the cabbage seedpod weevil, its lifecycle, and damage it incurs. It also outlines how to determine if the pest is a problem in your fields and recommendations for management.
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Winter canola acreage in central and eastern Washington continues to increase as more producers learn about the rotational benefits and potential profitability of canola in predominantly cereal-based rotations. With more acres in production, insect pests common in other canola-growing regions of the US and Canada are now being observed in the Pacific Northwest (PNW). While many of the pests are not at thresholds to warrant control measures, the cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham), is becoming a problem in some areas of Washington State.

The cabbage seedpod weevil (CSPW) is an introduced insect pest from Europe and causes damage to members of the Brassicaceae or mustard family, including cultivated crops such as canola and brown mustard. This tiny weevil can also utilize flixweed (Descurainia Sophia L. Webb ex Prantl), tansy mustard (Descurainia spp.), and hoary cress or whitetop (Cardaria draba L. Desv.) as food hosts (Dosdall et al. 2014).

These two common weed species are abundant throughout eastern Washington. When left unmanaged, the CSPW can cause significant damage to ripening canola seeds and impact overall yields by as much as 50%.

CSPW at a Glance

Host plants: Canola (including volunteer canola), brown mustard, flixweed, and hoary cress (i.e., whitetop).

Where to look for CSPW:

  • Adults: newly developing floral buds through pod development.
  • Larvae: inside the pods.

Pest thresholds: 20 adults from 10 sweeps at 10–20% bloom (Canola Council of Canada 2014), control measures needed to prevent from reaching damage levels equal to the cost of control (i.e., the economic injury level).

Pesticide treatment: Registered in-crop product examples: Besiege (chlorantraniliprole + lambda-cyhalothrin), Declare (gamma-cyhalothrin), Warrior II (lambda-cyhalothrin), and Mustang Maxx (zeta-cypermethrin). Seed treatment: Gaucho 600F and Gaucho 480 (imidacloprid).

  • Note: The above listed products are highly toxic to bees. Please pay particular attention to the information on Bee Precautions listed in the Chemical section of this publication. Refer to the online version of the Pacific Northwest Insect Management Handbook for up-to-date information on application rates and products. The entire pesticide label for each product is available at the Crop Data Management Systems website.

Description and Lifecycle

Like many weevil species, adults have a prominent, curved snout with elbowed antennae. The insects measure 3 to 4 mm long and are ash-grey in color (Figure 1). CSPW adults emerge in the spring from their overwintering sites (i.e., leaf litter or roadside ditches) where they have remained burrowed in the soil protected from freezing temperatures (Brodeur et al. 2001). Once emerged, they will begin to seek out favorable plant hosts (Figure 2).

CSPW adults can be found concentrated on newly developing flower buds of winter canola. Mating occurs in the spring until early pod development. When the small pods begin to develop (1–2 cm), the females chew a small hole into the pod wall and



Copyright 2016 Washington State University

Published August, 2016

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