Cutworms Winding Down?

Reports of cutworms continue in parts of Saskatchewan and Alberta. Reports of cutworms are most common in fields that were cultivated last summer (summer fallow or pasture and hay land that was renovated) and had loose soil (usually with some green growth present, including weeds, that attracted the moths to lay their eggs near a food source for the larvae when they hatched, either in the fall for some species (e.g. dingy cutworm) or in the spring for other species (e.g. red-backed cutworm). Cutworms should be nearing the end of their larval stages. Scott Hartley, Saskatchewan Ministry of Agriculture, advises that foliar feeding cutworms (e.g. dingy cutworms) should be beginning to pupate and no longer be feeding. Foliar feeding cutworms are usually a threat until about the third week of June so even with the cool spring should be pupating by now. Pale western and red-backed cutworms feed beneath the soil surface (clip plant stems) and are usually a threat until the end of June but with the cool spring conditions may remain a threat for another week to 10 days. In some areas though, the larvae may be at an advanced stage of development and close to pupation. Younger larvae pose the greatest potential for damage as they still need to feed and grow, with the greatest consumption in the late instars when they are larger with greater appetites. However, larvae are near pupating when they are 30 – 35 mm long and when cut open their gullet lacks green material. If no food is found, chemical control will be less effective as this is another indication that feeding is slowing and they are nearing pupation. Although some control may be achieved when treated plant material is ingested, control of the cutworms is usually a result of their movement to the surface to feed where they come in contract with the insecticide applied to the soil surface.

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