Varigated cutworm feeding on hosta
leaf. Note the yellow spots on the back.
hiding at base of hosta leaf on a cloudy day.
|Description and Biology:
The most distinguishing characteristic of the
variegated cutworm is the 4 to 7 pale yellow, circular spots on the back
of the larva. Its general body color is variable, but usually brown. The
underside of the caterpillar is cream colored. There is a narrow,
orange-brown stripe along the side. The adult moths have grayish brown
forewings and have a pale oval marking near the wing edge, adjacent to a
darker kidney-shaped marking.
The variegated cutworm overwinters in states to the
south of North Dakota. Moths migrate to the region during the spring and
summer months. There are multiple generations of this cutworm, numbering
two to three, depending on environmental conditions.
The variegated cutworm has a wide range of host plants
which includes field, forage, vegetable and ornamental plants. The
variegated cutworm is one of the most important cutworms on vegetables,
damaging potato and tomato.
Nearly all fruits, vegetables and ornamental plants
can be damaged by variegated cutworms. Damage is especially common on
hosta, petunia and other low growing, "fleshy_leafed" plants.
Feeding on hosta foliage causes large irregular holes at the leaf
margins or oblong holes within the leaf bounded by veins. Destruction of
emerging leaves at the center of the crown can be nearly complete.
Variegated cutworms large enough to cause noticeable
damage are usually at least 1/2 to 3/4 inch long. They ultimately grow
to be 1 1/2 inch. Like other cutworms, variegated cutworms are nocturnal
and feeding takes place at night or on very cloudy days, meaning few
people have seen the cutworms though many are familiar with the large
irregular holes noticed later.
Vegetable gardeners, homeowners with hostas, and
others are having a difficult time in eastern North Dakota due to a
large migration of variegated cutworm moths into the region this spring.
The variegated cutworm is found in sites as varied as alfalfa fields to
home gardens. This cutworm is referred to as a "climbing"
cutworm because of its habit of climbing plants at night to feed on
foliage, flowers, buds and fruits. Variegated cutworms do not damage
plants by clipping at ground level as is typical of many cutworms.
Control can be as simple as raking around the base of
damaged plants with your fingers until you find the culprit. The brown
cutworms blend well with the color of mulch and soil and careful
searching will be necessary. Searching for cutworms at night and
discarding all that are found feeding on plant foliage is another
possible mechanical control.
Larger problems with variegated cutworms can be
controlled by treating the soil around damaged plants with Sevin,
permethrin, cyfluthrin, bifenthrin, or diazinon. If treating vegetable
crops, select only insecticides approved for application to those edible