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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…
Canola Watch Posts
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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… -
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… -
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… -
When sweep netting for lygus, include late instar nymphs — the ones with black dots, as shown above — when doing counts for thresholds. Sclerotinia stem rot risk is still high in most regions. Fungicide labels allow for spray up to 50% flower. Spraying this late may work well if the crop seems to be flowering for a long time…
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Canola plants that lose flowers to heat, insects, etc., can recover without a yield penalty — or not much of one — if conditions improve by early to mid flower. The chart above shows that canola plants produce far more flowers than pods, providing a cushion… -
Include nymphs (shown above) when doing lygus sweep net counts. Bertha risk rising. Zebra caterpillers are usually confined to small areas within a field. (Photo source: Roy Ellis)… -
Fungicide labels allow for spray up to 50% flower (some are up to 30%). Spraying this late may work well if the crop seems to be flowering for a long time, or the crop is at various stages — either scenario leading to an extended time at 50% flower. Extended flowering does extend the vulnerable period for sclerotinia stem rot… -
Keep in mind pre-harvest intervals for fungicides and insecticides now that many early seeded crops are less than a month from swathing. Pre-harvest intervals vary widely from product to product…