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Flea beetles, cutworm numbers cause for concern

Manitoba Insect & Disease Update for June 6, 2018

Diseases: No disease incidents reported this week.

Insects: Flea beetles and cutworms continue to be the main insect concerns. Flea beetles are a concern in many canola fields and foliar insecticide applications are occurring in many areas. There has also been some reseeding of canola because of flea beetle feeding.

Now that cutworms are getting larger and their feeding more prominent, some economic populations have been detected.

Flea Beetles

Foliar insecticide applications to control flea beetles on canola have been occurring in all agricultural regions, and there are reports of some second insecticide applications for flea beetles.  There are also more reports of reseeding of canola because of feeding by flea beetles, particularly in the Southwest and Central regions.

How long does canola remain susceptible to flea beetles? A general guideline is that once the canola has 3 or 4 true leaves expanded, it can usually compensate well for feeding by flea beetles. Research in Manitoba found that yield was reduced most when plants were damaged during the seedling to second true leaf stage, but was not reduced  when they were damaged after reaching the third to fourth true leaf stage.

Cutworms

Cutworm feeding has intensified over the past week as cutworms get larger and their feeding more noticeable. There are reports of insecticide use for cutworm in oats, wheat, canola, corn, sunflowers and dry beans. Some of the heaviest feeding seems to be in the Central region and southwest. There are a couple of reports of patches in oat fields in the Central region being reseeded because of cutworm feeding. Redbacked cutworm seems to be the dominant species in some of these fields, although some dingy cutworms are being found as well.

How long will cutworms feed: If there are still a lot of cutworms under an inch long, then there is still ample time for higher populations to do economic damage. As a general guideline, once they get over an inch long they will be pupating soon and applying controls may be more expensive then the damage you are preventing.

Click here to read the full report on the Manitoba Agriculture website. Visit the Insects page on the Manitoba Agriculture website for more information and identification.

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