Manitoba Agriculture, Food and Rural Initiatives
Strawberry Cutworm II
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Biology
Cutworms are the immature forms of certain moths. All cutworm larvae have a round, dark head; six small, jointed legs just behind the head; and ten fleshy legs toward the rear. Strawberry cutworm larvae are cream-coloured with two prominent brownish-purple bands along the length of their upper surface. They reach about 3 cm in length at maturity.
Symptoms of Damage
The young larvae feed on the strawberry fruit stalks or leaf stems. Later, the larger larvae bore into the crown, killing the plant. They feed from late-May to mid-July. Pin point infestations by looking for patches of damaged plants. The symptoms include leaf feeding, cut-off plant stems, and wilting plants.
Monitoring
Remember that cutworms are nocturnal. Hiding in the soil and litter by day, cutworms climb the stems of strawberries at night and feed on buds, leaves, and fruit. Because most sampling occurs during the day, check around the bases of damaged strawberry plants for cutworm larvae. Look for the larvae just under the soil surface where the plant enters the soil. You may see recent feeding at the bases of some plants.
Pay particular attention to strawberry plants in older fields where cutworm damage will be most apparent. Populations tend to build up over the years, as a planting ages.
Economic Thresholds
No economic thresholds have been established for cutworms in Manitoba strawberry fields. Spot treatments may be made if larvae are found.
Comments
Because their populations are slow to become established, note that treatments made one year will likely reduce damage for several consecutive years. Although good crop management will produce healthy plants that are able to resist some cutworm damage, no specific methods will prevent damage. Fall renovation tillage, after the female moths lay their eggs in August, may kill some eggs that are hidden in the soil and loose trash. Completely ploughing under of an old planting that is heavily infested may knock out an infestation. Planting new fields next to infested fields should be avoided.
For further information, contact your GO representative.
