July 25, 2012 – Issue 22

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  • Issues of the week

    Bertha armyworm larvae have started to feed in some locations, and the second generation of lygus has arrived in the southern Prairie. Watch pods and upper foliage for signs of feeding, and scout all fields. While scouting, also look for signs of blackleg, clubroot and foot rot (shown above). Late season foot rot has shown up in some fields, with stems pinched off at the soil surface.


  • Photo quiz of the week

    What caused these misshapen pods?


  • Insect update: Lygus, bertha

    Second generation lygus have arrived. Young nymphs will reach late instar and adult stages in 5 to 14 days. When scouting to see if lygus numbers are near thresholds, include later instars — the ones with black dots on their back — as well as adults in the count. Bertha armyworm larvae are starting to feed in some locations.


  • Lots of green worms. What are they?

    Some fields may have a variety of green worms feeding, including bertha armyworm, diamondback moth larvae, imported cabbageworm and alfalfa looper. Here’s how to tell them apart.


  • Combining thresholds for multiple insects

    We don’t have scientific evidence to combine thresholds, but where an “additive” effect of multiple species can make sense is when more than one species are feeding on key yield-producing areas — flowers, buds or pods — at the same time.


  • Beneficials to look for while scouting

    Lygus, bertha armyworm and diamondback moth have a number of natural enemies that will keep populations in check. These beneficial insects may not control an immediate insect threat — growers will still have to spray if economic thresholds are reached — but beneficials can keep a lid on populations. The key to preserving beneficial insects is to follow thresholds and spray only when necessary. Here are some beneficials to watch for while scouting:


  • Swede midge identified

    Swede midge larvae have been found in misshapen canola flowers from fields in the northeast region of Saskatchewan. Symptoms included aborted flowers or flowers with petals apparently fused or glued together, and misshapen, stunted or sometimes missing pods. Racemes appeared normal except that some flowers had fused petals that did not open, suggesting a later infestation that should limit any impact on yield.


  • Disease update: Blackleg, sclerotinia, foot rot, clubroot

    Sclerotinia could be bad this year but the window to apply fungicide has closed for most crops. Rhizoctonia foot rot, shown above, may explain some toppling plants. The weeks leading up to harvest are a good time to scout for blackleg and clubroot.


  • Lots of aster yellows

    Fields all across the Prairies are reporting aster yellows. The phytoplasma infection causes misshapen pods and flower buds. Most fields don’t go above 1% infected plants, however, some fields are reported this year with rates at 5% to 8% of plants infected. A 10% infection rate results in 3% to 7% misshapen seeds or no seeds at all.


Canola Watch