Steady rain and cooler temperatures help the Michigan canola crop along

Madelyn Celovsky<celovsk2@msu.edu> and Christine Charles<charl122@msu.edu>, Michigan State University Extension - June 06, 2025

Updates from the field on canola crop progress, insect pests and crop disease.

Canola crop on the left finishing the flowering stage. Canola crop on the right has reached its final size and is beginning to fill. — The canola crop is finishing flowering (left) and entering seed development where pods reach their final size and begin to fill (right). Left photo by Christine Charles, MSU Extension. Right photo by Jason Stegink, Wide Angle Agriculture

Though canola acres in Michigan are limited, this time of year they attract quite a bit of attention because of the flashy yellow flowers. Crop scouts from across Michigan’s winter canola growing region reported how the canola crop is progressing.

Crop progress

Moving through flowering, the canola is now in seed development stage as pods reach their final size. At this point, plants are using energy reserves stored in the stem. Canola tends to be quite resilient through flowering stages. Though canola growing areas experienced one instance of light frost conditions earlier this month, scouts in Michigan did not report frost damage. Agriculture and Agrifood Canada reports at flowering, temperatures need to be above 85 degrees Fahrenheit to reduce yield.

Once the crop gets to seed development, canola becomes more sensitive to stressful conditions. Environmental or biotic stressors like extreme heat or extensive pest feeding can cause the crop to abort pods. Canola water use reaches its peak at seed development. This year, temperatures have remained relatively cool throughout flowering and the beginning of seed development and canola growing areas have generally received sufficient rain.

Insect pests

At seed development, few management interventions make economic sense. However, this is a good time to scout for insect pod feeding by cabbage seed pod weevil larvae and lygus bugs. Earlier in the season, scouts in the Hickory Corners and Jackson, Michigan, areas found adult cabbage seed pod weevils and lygus bugs below action threshold. Scouts did not report any pod feeding at this time.

Weeds

Early in the season, weeds compete with canola plants for water, nutrients and sun. At this point in the growing season, escaped weeds may impact crop quality. White campion (Silene latifolia) can compete with canola throughout the season and, if allowed to go to seed, can cause crop quality issues. Scouts in Jackson report some weed pressure from white campion and volunteer wheat. Herbicide applications are not advised at this point in the season. However, knowing what weeds are present and producing seed this year can help guide future weed management decisions.

White campion growing through canola. White campion seeds compete with canola and can cause crop quality issues when it goes to seed before canola harvest. Photo by Madelyn Celovsky, MSU Extension.

Disease

White mold or stem rot (Sclerotina sclerotorium) can impact canola. The main management tool for white mold in winter canola is a fungicide application at flowering. Scouts report fungicide applications progressed through flowering, despite spotty rains. White mold is particularly a concern when winter canola is planted following soybeans. Check out the Sclerotinia Stem Rot of Canola fact sheet from Oklahoma State University for more information.

Powdery mildew (Erysiphe cruciferarum) can also be present. Scouts in Jackson found signs of powdery mildew. Powdery mildew has not been reported to impact canola yields in Michigan in previous seasons.

Though scouts did not report catching any aster leafhoppers, one scout did report some symptoms of aster yellows, a phytoplasma spread by the leafhopper. When infected, flowers and pods are replaced by sterile, vegetative growth. Aster yellows has not been reported at levels high enough to impact canola yield in Michigan, and no leafhoppers carrying the phytoplasma have been blown in from the south early in the season.

Vegetative growth in place of flowers (circled in red) on a canola plant. — Aster yellows infection, a phytoplasma spread by aster leafhoppers, can cause vegetative growth in place of flowers (circled in red). Photo by Madelyn Celovsky, MSU Extension.

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).