Canola Watch: Cabbage seedpod weevil | Sclerotinia spray pre-planning | What’s wrong with my canola?

In this Canola Research Hub video, Dr. Hector Carcamo, research analyst with Agriculture & Agri-Food Canada in Lethbridge, Alberta, discusses common questions and research related to two common pests in canola: lygus bugs and cabbage seedpod weevils.

What is this week’s insect of concern? 

Cabbage seedpod weevil is the biggest concern in many fields, especially in southern and into central Alberta and Saskatchewan where canola is beginning to flower. Do not spray too soon. Damage does not occur until pods are large enough for egg laying, and insects will continue to invade the crop for 7-10 days or more after first flower. Proper insecticide timing is when the crops are at 10-20% flower (70% of plants have 3-10 open flowers), both to best manage yield loss and to minimize damage to pollinators. Spray only if numbers exceed the economic threshold. If an application is necessary, only use insecticides registered for control of cabbage seedpod weevil in canola and always read and follow current product label directions. PMRA’s new label update limits the use of lambda-cyhalothrin. Learn more about the label update, CCC’s advice and alternative products here. (Cabbage seedpod weevil) (Insecticide control options)

“2023 could still easily be the year of the bug, even if it wasn’t the year of the flea beetle in most canola fields,” says CCC agronomy specialist, Keith Gabert. Warm weather through May likely contributed to higher early season insect activity and may result in higher populations of multiple insects through portions of the growing season. Green worms of multiple types, alfalfa loopers, blister beetles, lygus bugs and diamondback moths are all now appearing.
 

What’s wrong with my field? How to get the most from a patchy / variable field?

Lack of moisture, especially in southern and eastern MB, is causing field-wide stress in some areas and patchiness in others. Cutworms, root rots (which are often confused with cutworms), and Group 2 injury are also contributing to poor stands. Mystery syndrome (aka: floral disruption or hormone imbalance syndrome), which may be caused by a combination of stress factors including cold shock at bud formation, is appearing as aborted buds and purple and twisted leaves. Confused about what is causing plant stress or growth challenges in your field, and/or seeing bud abortion? Send photos to your region’s CCC’s agronomy specialist. (Sad or odd looking buds, flowers and pods) (Plant populations: How to count? Why low?)

In fields with variable staging, consider: which parts of the crop offer the highest yield potential? That answer is not always easy. Higher yield may not come from highest number of plants: depending on precipitation timing, heat stress and other factors, later maturing plants – even if fewer in number – may produce more yield if they suffer less stress. 
 

How much risk warrants a sclerotinia spray application? 

Canola’s #1 disease will need to be top of mind in many fields by next week. The sclerotinia spray must occur between 20% and 50% flower, with the decision based on these risk factors leading up to and during that window. Patchy precipitation will likely make this year’s spray decision more challenging. In currently dry fields, ask: if precipitation falls soon and the crop starts flowering, is there enough yield potential to justify a fungicide application? Given the $20-$30/acre cost of application, a fungicide application must preserve at least one to two bu/ac to meet its economic threshold. Typically, yield loss is half the percentage of plants infected in a field (ie: if 10% of plants are infected, expect 5% yield loss). (Top 10 sclerotinia stem rot questions) (Podcast: Sclerotinia spray decision) (Sclerotinia fungicide improves yield but check ROI)

To help growers decide whether a fungicide application is advised to control sclerotinia, the CCC is updating our sclerotinia risk assessment checklist into a validated and interactive tool. The CCC is looking for beta testers to use the tool during early flowering in 2023, and then revisit fields during 30-60% seed colour change to assess sclerotinia disease severity to confirm the recommendation. Testers who complete both steps will be eligible for a gift card. To sign up as a beta tester, email Chris Manchur, CCC Sclerotinia Lead.

How to time a variably staged crop?

Variable staging, whether from inconsistency at emergence or stresses in the growing season, will make top dressing, fungicide, insecticide and weed control timing more difficult… but especially critical. Be vigilant and pre-plan so sprayer passes can occur as soon as economically necessary. Now is the time to closely assess herbicide efficacy. Invest time in scouting. If misses occurred, manage those weeds now – hand pulling while they are small solves what will become a major problem once those weeds set seed. A variably staged field is more likely to require a second herbicide pass, but the window is quickly closing for application. To prevent herbicide injury, stage spray timing based on the most mature canola plants in the field. Always follow the label. Top-dressing nutrients must happen almost immediately if at all. Stabilizers are available if top-dressing into dry conditions. (Second pass herbicide why and when) (Weed control strategies for each HT system) (How to use technology to manage yield)
 

Canola 4R Advantage year two: Applications open on June 26.

The CCC will start accepting applications for year two of Canola 4R Advantage on June 26. The program offers financial support to growers as they initiate or advance 4R Nutrient Stewardship on their farms. The new, user-friendly digital application portal will be available here, and will allow growers to check the status of their participation through all stages of the process, from applying to submitting claims.

To prepare, visit canolacouncil.org/4R-advantage to view the CCC’s recorded webinar covering program changes and updates for year two, as well as a demo video on how to apply.