Canola and Mustard Chapter XVI

Cabbage Seedpod Weevil

Sue Blodgett & Greg Johnson

Weevil adult, left; larva, right.

Cabbage seedpod weevil was first detected in Montana in 1999 and has been in southern Alberta since 1996.  It has been an important pest of canola in the northwestern US. 

Identification (and Life cycle/seasonal history)

The adult CSW is a small, 2.5 – 3 mm, gray or black beetle with a strongly curved beak. Adults overwinter in protected sites or just below soil surface becoming active in the spring.  After emerging from overwintering site adults feed on early growing weedy mustard family plants.  Females move into and lay eggs on canola pods.  Eggs begin hatching within 5 days.  Larvae burrow into the pod where they feed on developing seed, consuming between 5-7 seeds.  When feeding is completed the larva chews a round exit hole at the base of the pod and drops to the ground to pupate.  New adults emerge within 2-4 weeks and may feed lightly on canola plants before seeking out a protected site to overwinter. 

Plant Response and Damage

CSW was found to be the major late season pest of rapeseed in Idaho in 1992.  In 1993, the major late season pests were aphids and diamondback moth.  An estimate of the combined insect damage in those years was 37% yield reduction.  Unsprayed fields where CSW is common generally suffer 15-35% yield loss (Univ. Idaho).

Polish, Argentine and brown mustard (Brassica juncea) are susceptible to CSW while yellow/white mustard (Sinapis alba) is resistant.

Sampling

Sampling adult CSW should occur between bud stage and the end of flowering.  Each sample consists of 25, 180o sweeps.  Sampling should be conducted at weekly intervals until pods have formed and flowering is completed.  CSW can be more abundant on the field edge so samples taken at least 200ft or more from edge will be more representative of the whole field.  

 

Management Strategies

When 3-6 adult weevils per 180-degree sweep are detected or when 2 or more insects can be found per plant on young pods treatment is warranted. 

 

Product List for Cabbage Seedpod Weevil:

Pesticide

Product/Acre

Preharvest Interval, Remarks

 

Capture 2ECR,1

2.1 – 2.6 fl oz

 

35 days. 12 hr REI.  Do not apply more than 5.12 oz /A /season. Do not make applications less than 14 days apart.  See label for minimum gallonage.

 

Gaucho 600 3

15.36 – 25.6 fl oz/cwt

 

 

Lambda-cyhaolthrinR,1,2

1.92-3.84 oz (Warrior with Zeon)

1.92-3.84 (Lambda T)

7 days, 24 hr REI. Avoid application when bees actively foraging by applying early morning or evening. Do not apply more than 0.72 pt/A /yr. See seasonal use rates for gamma and lambda cyhalothrin.

 

ProaxisR,1,2

1.92 - 3.84 oz

7 days, 24 hr REI. Do not apply more than 0.72pt/A/season. See seasonal use rates for gamma and lambda cyhalothrin.

 

1 Label allows chemigation,
2 Generic active ingredient, several formulations available, see labels for rates
R Restricted use pesticide

 

 
The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.

 

Categories: Canola, Mustard, Insects, Cabbage seedpod weevil

Date: 06/06/2006