Issues of the week

July 5, 2012 - Issue 19

Regular rains in June and so far in July suggest an inflated risk for sclerotinia stem rot this year, especially in dense stands with good yield potential. Careful when making disease assumptions based on the low disease incidence last year. Sclerotinia stem rot may have been lower than expected in some regions last year because rains during flower were heavy enough to either wash petals off the plants or saturate the soil leading to reduced apothecia production or spore release, disrupting the infection process. In other regions, such as the eastern prairies, precipitation dropped well below normal in the latter part of the summer, reducing the opportunity for fungal infection and development. Growers may consider the lower split rate of fungicide for sclerotinia management if (1) the risk is only moderate at early flower and growers want the opportunity to spray again if the risk increases as the crop approaches 50% bloom or (2) the crop is uneven and the flowering period could last longer than usual.

Some canola fields are under pressure from more than one insect species. If those species are not at control thresholds on their own, but together exceed thresholds, then a spray may be warranted — as long as both species are feeding on the same part of the plant.

Nutrient top ups just prior to or at early flowering may still provide an economic payback, even though it’s not ideal timing.

Extreme weather in the past week included heavy rains, hail and wind. Heavy winds bent over some canola and caused stems to grow in an “S” shape as plants turned back skyward. Curved stems should not cause any reduction in yield potential, provided they are not kinked or physically damaged (e.g. hail scars) so as to disrupt moisture and nutrient flow. The only consideration may be that pods are closer to the ground at maturity, so you may have to swath lower.

Canola Watch