There are no particular conditions that cause cutworms to attack some plants rather than others. However, soil that is too poor to host beneficial insects that prey on pest eggs and larvae and the absence of predator birds in and around your yard allows cutworm populations to flourish and cause more extensive damage.
Some cutworms are always present in the soil in most home landscapes, because adult moths are common in these areas. The larvae reside under the turf in lawn areas and in vegetable gardens as well. They often recur in the same areas, especially where there are dense clumps of weeds and long grasses. New young seedlings and grass roots are perfect food for cutworms as they grow to a size to prepare to pupate and become moths.
Cultivate Soil in Spring
Reduce cutworm problems in planting beds where they are a nuisance by intensely cultivating the soil there for 1 or 2 seasons. In early spring remove winter mulch to expose the soil to sun and air so that it dries out and warms a bit. As soon as the soil is dry enough to work without forming sticky clumps, cultivate it thoroughly with a hand cultivator or small power tiller.
Turning the top layer of the soil over exposes any cutworms in the soil so they are easy prey for birds and other predators living in your yard. Early cultivation also eliminates any young weed seedlings which provide the first food for young cutworms in the spring. Once you improve the soil quality in these areas, you will not need to cultivate so vigorously, because natural predators in the soil will attack cutworm eggs there.
Attract Beneficial Insects to the Yard
Birds, spiders, and predator insects prey on cutworms, killing many more than homeowners ever can. Improve your soil by adding organic matter so lots spiders and ants can survive there and eat cutworm eggs. Avoid using broad-spectrum insecticides in your yard for other pest problems so that natural populations of beneficial insects which prey on cutworms and other pests are not inadvertently killed too.
Insects such as braconid and trichogramma wasps, ground beetles, firefly larvae, soldier beetles, stinkbugs, and tachinid flies all prey on cutworms in their various life stages. More of these desirable beneficials will come to live in your yard if you have a variety of flowering plants that provide them nectar and pollen.
Encourage Birds Year Round
Next to beneficial insects, songbirds consume the most pest insects in your yard. These include swallows, blackbirds, bluejays, brown thrashers, meadowlarks, robins, sparrows, and wrens. Chickens like cutworms, too. At nesting time even seed-eating birds such as sparrows and finches hunt for insects to feed their young. A single pair of sparrows that live in your yard may have 3 broods of 3 to 4 young a season. The parents must collect vast numbers of insects in your yard to feed them. To enlist the birds’ help in your fight against pest insects, provide food, water, and shelter for bird families.
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