Lygus hotspots: Lygus numbers are high in some regions, with reports of 70+ per 10 sweeps in some fields in central and northern Alberta. Some fields will warrant a spray, but seeing the plane next door does not mean all canola in the area should get sprayed. Assess each field. Bertha armyworm hotspots: Berthas are a very low numbers in…
Insects
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Threshold tables for lygus suggest, for example, that if canola is $12 per bushel and spray costs $8 per acre, the threshold at the early pod stage is 5 lygus adults or late instar nymphs per 10 sweeps. Current thinking is that 5 lygus per 10 sweeps (0.5 per sweep) is too few to warrant a spray, and that the…
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Thresholds are 100-150 larvae per square metre in immature to flowering plants and 200-300 larvae per square metre (20-30 per square foot) in plants with flowers and pods. While these nominal thresholds are based on dense stands of 150-200 plants per square metre, plant population is not a major factor. Fewer plants will have more branching and more pods, so…
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When strange patterns of damage in canola fields line up perfectly with the sprayer boom width or follow typical drift patterns, phone calls and finger pointing begin. Explanations can be simple: The wrong product was added to the tank, or the right product was applied but on the wrong field. But situations are often much more complicated — and made…
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While insects are not a major threat in most fields at this point in 2014, diamondback moth larvae are around, cabbage seedpod weevil are still laying eggs, and bertha armyworm larvae have been found in some locations — although at very low levels for the most part. (See the Map of the Week.) Here is a review of thresholds for…
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The goal when spraying cabbage seedpod weevil (CSPW) is to stop adults from laying eggs in newly formed pods. CSPW don’t do their damage until pods are at least 1” long — so aim to spray just prior to that stage, at about 20% bloom. By late July, adults have been around for two months and are coming to the…
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Beneficials. 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 pest threat that has already exceeded thresholds — growers will still have to spray in that case — but beneficials can keep a lid on populations. The key to preserving beneficial insects is…