Problem type: Insect
Name of problem: Cutworms
Plant name(s): Field
crops, vegetables, lawn, home garden plants
Symptoms / Characteristics:
Cutworms feed on the base of plants, cutting off the stems
near the ground. Damage on grass plants may appear like sunken pocket
marks and seedlings or other herbaceous plants may show signs of wilting.
Short stems may be left or they may be cut off below the soil line. Holes
and notches may be chewed in leaves, as some cutworms will climb the plant.
Their life cycle consists of an egg, larva, pupa and adult stage. Generally
there is one generation per year. Adult moths can lay hundreds of eggs
on host plants. They can overwinter in any stage but eggs are most commonly
laid in late summer and overwinter in this stage. The eggs then begin
to hatch around May and larval feeding begins by June. This spring generation
of larvae is the most damaging as plants are just starting to grow. Larvae
feed for a couple of months growing from 3-5 cm long. Cutworm larvae usually
have a variegated appearance being dull in color with reddish, brown or
pale stripes along the entire length of the body. Cutworms are nocturnal,
feeding at night and hiding during the day making them hard to detect.
Cutworm larvae are known for their C-shaped, curled position, especially
when disturbed. Larvae tunnel in the soil to pupate, and emerge shortly
as adult moths in August.
On the prairies, strawberry cutworms
may be of particular concern. The larvae of strawberry cutworms are whitish-yellow
with a pair of thick, brownish-purple stripes running lengthwise along
the back. They can reach a mature length of approximately 30 mm. Immature
larvae begin feeding on leaf and fruit stems. Once mature, they begin
boring into the crown of the plant. This activity typically results in
plant death. Wilting symptoms associated with strawberry cutworm feeding
are often confused with winterkill. Damage is most severe in older, more
mature plantings where larger populations of cutworms have become established.
Control / Preventions:
Inspect plants starting in May through to July. Look for
the larvae just below the soil line, down to about 2 inches. Look for
signs of feeding on stems, petioles and leaves. Plants may appear wilted
and will pull out of the ground quite easily. Adult moths are nocturnal
and attracted to light. Light traps can be used to reduce adult populations.
Small populations of larvae can be controlled by digging them up and removing
them from the soil. A single larvae can destroy many seedlings in one
night, so only a few cutworms per square meter can destroy thousands of
seedlings in a week. In instances of high population levels, insecticides
are available. An application of a commercially available cutworm dust
can be applied. Spraying with insecticides are most effective against
young larvae. These should be applied in the late day or evening when
cutworms are most active. Spot applications should be made where damage
is confined to one area.
Proper cultural practices can help to prevent cutworm infestations. Removing
weeds and mowing grass low in the fall can prevent egg-laying sites for
the adult females. Cutworms can feed on vegetables and fruit, so keeping
branches from touching the ground and keeping the ground mowed under the
plant will reduce the chance of invasion. Remove all debris, mulch and
till the soil 4 inches deep in the fall and spring as they overwinter
in the soil. To protect individual plants, placing containers into the
soil about 2 inches deep around the base of the plant can prevent larval
feeding. Inspecting plants early and catching cutworm larvae while they
are young and few will provide the most effective control.
Relevant web sites: