Insect update

,Cabbage seedpod weevil

Adults have arrived and are feeding on volunteer canola at the bloom stage in southern Alberta and southwest Saskatchewan. Weevils move to canola fields at the bud to early flower stages. Growers should start scouting.

The proper way to scout for cabbage seedpod weevil adults is with a sweep net. Begin sampling when the crop first enters the bud stage and continue through the flowering period. Select 10 locations within each field and at each location, count the number of weevils from ten 180° sweeps. Sample both the perimeter and interior of the field to obtain an accurate estimate of weevil numbers throughout the field. Click here for more detailed information on proper sampling techniques.

The economic threshold for the weevil is 20 to 30 in 10 sweeps, depending on crop price.

It is important not to spray too soon, as the weevil will typically continue to invade for at least a week to 10 days after the first flowers open. The optimum time to spray for cabbage seedpod weevil is early flowering (10% flower if possible). Spraying at 10% flower will allow the weevils more time to move into the field, while at the same time it is still early enough to keep them from laying any significant number of eggs in the newly forming pods. Spraying after 10% flower when populations are at or above threshold may not only result in yield loss, but will also impact beneficial insects including pollinators who have moved into the field. It is important to keep in mind canola’s ability to compensate for weevil feeding on buds and stems where moisture is not limiting. Where moisture constraints are present, the ability to compensate may be reduced, and using the lower end of the threshold range may be appropriate. The Prairie Pest Monitoring Network provides identification and more monitoring tips: 2010_CSPW protocol

Scott Meers of Alberta Agriculture & Rural Development is recruiting scouts and crop consultants to enter cabbage seedpod weevil data into an online survey. This data will populate a google map that will show weevil hotspots in real time. Call 310-2777 (only in Alberta) and provide name, sample date, location (LLD or GPS), total number of sweeps,  and total number of weevils in those sweeps.

Bertha armyworm

Adults showing up in traps across the Prairies. Numbers are on the rise, so start watching fields for larvae as fields are coming out of flower.

Diamondback moth

Eastern Manitoba has high counts of adult moths and numbers are on the rise in other locations. Now is the time to start scouting and watching your fields on a regular basis so you can watch for economic thresholds of larva if required.

Root maggot

High counts are reported in some parts of western Saskatchewan and the sandier land in Manitoba. If you see sick-looking canola plants starting to wilt, pull up a few and look at the root. Look for tunneling along the root. There is nothing that can be done to control maggots now, but canola on canola can increase the risk. Fields with high maggot populations may benefit from an extended break from canola. Higher seeding rates should be considered to reduce the overall feeding damage on a per root basis.