July 4, 2013 – Issue 14

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  • Issues of the week

    July 3 high

    It’s looking like a hot week across the Prairies. The map above shows the highs for July 3, with many regions with highs of 30C+. (Click on the map for a bigger version.) Canola doesn’t like heat, especially at flowering. Heat can cause bud and flower blasting, resulting in blank pods and lower yield. But heat isn’t the only possible cause, as you’ll read in the article below.

    Hot and dry temperatures can also reduce the sclerotinia stem rot risk, but heat alone does not lower the risk substantially if fields had average to above average moisture before, and if the canopy continues to have morning dew and high humidity.

    Sclerotinia stem rot management begins as canola comes into flower. Canola with average to above average yield potential and good soil moisture are at higher risk, and could see an economic return from fungicide.

    Cabbage seedpod weevils seem to be moving north and east in Saskatchewan this year, with canola fields near Moose Jaw and just south of Outlook having the insect at higher numbers. The time to spray, if thresholds are at 2+ weevils per sweep across the field, is around 20% bloom.

    Follow @CanolaWatch on Twitter. Here’s our pick for Tweet of the Week:

    Tweet of the week July4


  • Quiz

    Quiz July 4

    Why are the two halves of this field so different?


  • Diamondback moth scouting tips

    Diamondback moth larvae feeding on pods.

    The most accurate method to estimate diamondback moth population density in canola is to count larvae in several locations throughout the field, and determine the average population per unit area.


  • Heat alone will not eliminate sclerotinia stem rot risk

    Moisture has a much larger influence than temperature when it comes to sclerotinia risk. 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. Dew and high humidity can provide enough moisture for sclerotinia stem rot. If your pants get wet walking canola fields in the morning, there’s enough moisture for the sclerotinia infection cycle.


  • Heat blast and 6 other causes for missing pods

    Heat injury to pods.

    As canola starts to move from flowering and into pod formation, growers will often notice blanks up the raceme where pods did not form. Here are 7 possible reasons.


  • Cabbage seedpod weevil: Spray decision tips

    Orange and red areas are where cabbage seedpod weevil are at higher risk for canola yield loss. This area may be moving north and east slightly this year. Source: Owen Olfert, AAFC

    Cabbage seedpod weevil numbers are high in some regions of southern Alberta and southwestern Saskatchewan. The map shows CSPW reach for 2012. Growers and agronomists are encouraged to scout canola fields, and follow these management decision-making guidelines:


  • Weevils and lygus feeding together. Threshold?

    Cabbage seedpod weevil

    Many canola fields have a combination of insects feeding on the crop. An “additive” effect is possible when more than one species are feeding on key yield-producing areas — flowers, buds or pods — at the same time. For example, lygus and cabbage seedpod weevil have been found in the same fields in the southern Prairies this week. Preliminary results from an AAFC study suggests some basis for recommending control when you have moderate levels of the two pests. A nominal threshold of 15 weevils per 10 sweeps and 15 lygus per 10 sweeps has been suggested when both are present and feeding. (The threshold for cabbage seedpod weevil alone at early flowering is 20 per 10 sweeps.)


  • Leafhoppers building

    The aster leafhopper (species Macrosteles quadrilineatus) has 4 distinct black lines on its head. You can see these lines with a magnifying glass.

    Leafhopper populations are building, which could increase the risk for aster yellows. Even so, there is not really a good case for spraying for leafhoppers in canola. Why not?


  • Top-dressing at early flower

    Pale flower colour can hint at sulphur deficiency. This photo shows sulphur deficient flowers on the right, normal on the left.

    The ideal time for a sulphur top up is any time before flowering, but a top up at early flowering may pay off if plants are showing signs of sulphur deficiency.

    The ideal time for a nitrogen top up is before the 5-leaf stage of canola, but AAFC research out of Indian Head, Saskatchewan, shows that nitrogen top dress as late as 5-10% flower can still provide a yield benefit.


  • Top 10 reasons to manage for sclerotinia stem rot this year

    Rainfall from June 21-27 was average to above average for a lot of the Prairies. This means a lot of apothecia will be germinated and ready to release spores into canola crops flowering this week.

    Three of the top 10 have to do with moisture, the key risk factor for sclerotinia stem rot.


Canola Watch