July 11, 2012 – Issue 20

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  • Issues of the week

    More aster leafhoppers are carrying phytoplasm this year, so that could mean a jump in aster yellows. Sclerotinia stem rot risk may still be there even if it hasn’t rained. When spraying in high temperatures (> 25 C), check product labels or consult retailers or fungicide companies about results in hot weather. Late flower and podding stages are when lygus feeding causes the most damage…. Missing pods are a sign of lygus damage, but missing pods can have many causes, including other insects, heat, excess moisture, and herbicide damage.


  • Photo quiz of the week

    What caused these droplets to form?


  • Heat alone will not eliminate sclerotinia stem rot risk

    When it comes to the sclerotinia stem rot risk, moisture has a much larger influence than temperatures. Infection can be high in hot weather as long as the moisture is there. Moisture can come from rain, relative humidity in the high 80s, or morning dew.


  • Rescue treatments for heat, hail

    Heat — Foliar boron applied at flowering has been tested on canola in Ontario to as a way to prevent blossom blast during summer heat waves. Four years of grower field studies from 2008-11 found inconclusive results. Hail — Nutrient and fungicide top dress treatments have also been promoted to help heal and restart canola after hail. We don’t have published studies on using these treatments for this purpose in Western Canada, so it’s buyer beware.


  • Insects: Canola can handle some lygus feeding

    Our current economic threshold tables for lygus in canola may be too low when applied to current canola production systems across the Prairies. If a canola stand is healthy and growing fast, growers are reportedly doubling or tripling thresholds. Say the threshold is 10 per 10 sweeps, some growers are doubling that to 20 per 10 sweeps as the action threshold. Interestingly, a small amount of lygus feeding may actually encourage the plant to produce more buds.


  • Insects: Leafhoppers, berthas, blister beetles, cutworms

    Leafhoppers are more plentiful and carrying more aster yellows phytoplasm this year, but spraying is rarely effective. Bertha counts are starting to spike in some locations. Cutworms are still feeding in some locations, but the threat should be over for most regions.


  • Missing pods can have many causes

    Any stress can inhibit proper fertilization of the flowers. Common stresses included heat, drought, excess moisture, insects, herbicide damage, and nutrient deficiency. In many cases the cause may seem obvious, but it is often a good idea to investigate further to ensure there are no other contributing factors.


  • Blackleg heavy in parts of Manitoba

    Growers are encouraged to check maturing crop for blackleg infection. It’s too late for fungicide to provide any benefit, but checking now can help plan for next year. Try to figure out why blackleg is worse than usual. It could be tight rotation. It could be use of a less resistant variety. Take steps to avoid that situation next time.


  • Coming events

    Read more for events, including Canola Galla, Wednesday, July 25 in Brooks-Bassano. This hands-on field event is for agronomists, growers and all others interested in learning more about canola.


Canola Watch