Questions of the Week

Will it pay to spray for sclerotinia?

With precipitation spotty in many areas and canola now entering or partially through bloom, many growers are struggling with whether or not to spray for sclerotinia. The sclerotinia spray decision should be an ongoing process of reassessment; not a ‘once and done’ decision. Base assessment on these risk factors. (Risk assessment tools: Precipitation forecasting / Prairie soil moisture maps / Alberta sclerotinia risk map / Manitoba Agriculture’s Canola sclerotinia treatment decision calculator)

Given fungicide’s $25-$30/acre cost of application, a spray pass must preserve 1-2bu/acre or more to offer return on investment. It is difficult to evaluate yield near the end of the season, let alone at bloom. The best way to predict yield potential is to consider inputs: how much precipitation has fallen? How much fertility exists in the soil? Low plant counts can still deliver yields above 40 bu/ac and therefore may still warrant fungicide protection when disease risk is high. A variably staged crop may benefit from a split fungicide application. (Sclerotinia fungicide improves yield but check ROI) (Managing sclerotinia in oilseed and pulse crops) (Sclerotinia stem rot)

How, when and whether to tackle grasshoppers?

While some pests are easy to overlook, grasshoppers – which burst off plants and ping off vehicles – are nearly impossible to ignore. Still, the decision of whether to spray for grasshoppers should be based on the same best management practices that govern all insect spraying: careful identification and a threshold. Many grasshopper species prefer specific host plants, so identify species and assess crop damage first. If damage is present, the action threshold for grasshoppers in canola is is 8-12/m2. This number is under review as Dan Johnson, the ‘Grasshopper Guru’ suggests it could be as low as 5/m2 (unpublished). The Prairie Pest Monitoring Network recommends this grasshopper monitoring protocol. Because it is very difficult to accurately count grasshoppers, estimating numbers may be necessary. Scouting when grasshoppers are immature is easier, as grasshoppers whose wings only partially cover their abdomens hop rather than fly. Rain typically helps keep grasshoppers at bay; high heat will help nymphs mature more quickly. (Prairie Pest Monitoring Network grasshopper historical risk maps) (Label update for lambda-cyhalothrin)

Is there any way to reduce heat stress / flower blasting?

Canola does not do well when high environmental temperatures occur leading up to or during flowering. When the mercury exceeds 28 to 30°C (especially if warm nights above 16°C don’t allow opportunity for recovery), canola undergoes stress that causes a breakdown in communication between the plant’s various reproductive parts. This breakdown leads to flower blasting and aborted pods. Heat stress that impacts seed formation can occur in a plant’s early reproductive stages, well before flowers are actually visible, and/or at any point during flowering. While heat stress up until the end of flowering impacts the overall number of seeds, heat (and other stresses) later in the season impact size of each seed and overall quality. Unfortunately, research to date shows no evidence that any products promoted as heat stress aids or ‘cures’ are effective. If you choose to trial a product in hopes it will reduce heat stress, leave a check strip to calculate ROI. There are many reasons for missing pods other than heat stress.

What would you like to learn this tour season?

The CCC, various grower associations, research facilities and others will be hosting a wide variety of field tours and learning opportunities throughout the summer. These events are an excellent chance to build agronomic knowledge, learn about new opportunities, get questions answered, and make connections to others in the industry. Our weekly Community Connections, summarized in our newsletter and offered in full detail on our website, provides a listing of almost all canola and canola industry related events prairie-wide. Check it out here.