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University
of Rhode Island GreenShare Factsheets
Cutworms Lepidoptera:
Noctuidae
The
larvae or caterpillars of some moths are called cutworms (Agrotis,
Amathes, Peridroma, Prodenia spp.) because
of the manner in which they cut down young plants as they feed.
The adults are night-flying moths which feed on nectar, if at all,
and do no damage. There
are a great many species of cutworms. While they all feed on plants
by chewing, they vary as to damage done and host plants preferred.
Generally they destroy more of the plant than they eat. Their numbers
vary greatly from year to year and, when numerous, may destroy as
much as 75% of a crop. Cutworms injure plants in four major ways:
-
Solitary surface cutworms cut off young plants at or slightly above
or below the soil line, sometimes dropping the severed plants into
their burrows. Because most of the plant is not eaten, these cutworms
do great damage, attacking and felling new plants nightly. The black,
bronzed, clay-backed and dingy cutworms are in this group. -
Climbing species, usually the variegated and spotted cutworms, climb
the stem of trees, shrubs, vines, and crops and eat the leaves,
buds and fruit. -
Subterranean species, particularly the pale western and glassy cutworms,
remain in the soil and feed upon roots and underground parts. -
Army cutworms occur in great numbers, consuming the tops of plants
and then "marching" on to other fields. The
many species of cutworms can be quite distinct. Many are stout,
smooth, soft-bodied, plump caterpillars. These vary from brown or
tan to pink, green or gray and black. Some are all one color, others
spotted or striped. Some larvae are dull, others appear glassy.
The adults are generally very robust brown or black moths showing
various splotches, blotches or stripes in shades of gray, brown,
black or white.
Most cutworms pass the winter as partially grown larvae. Thus they
are already large, voracious feeders when transplants and seedlings
are set out in the fields. A few species pass the winter as pupae
or hibernating moths. Overwintering cutworms may live under trash
or bark, in clumps of grass or in earthen cells in the soil. These
cutworms become active and begin feeding as the weather warms in
spring, remaining hidden under debris or in the soil and feeding
at night. Many species continue to feed well through June, then
pupate in the soil to emerge later as moths. Normally there is only
one generation per year. The moths crawl from their brown pupal
cases in the soil and climb up through the soil, following the tunnel
made by the burrowing larva. If this tunnel is blocked, the fragile
moth cannot escape the soil. Cutworm abundance and development is
greatly affected by weather, especially rainfall. The moths mate
and lay eggs in late summer, beginning the next generation. The
moths often seek out grassy or weedy areas to lay their eggs, which
are usually deposited on plant stems or in the soil. One female
may lay hundreds of eggs. The hatching larvae feed until cold weather
and then hide for the winter in a sheltered, dry place. Several cultural
practices may offer some degree of control: - Plow and
fallow fields in mid- to late summer to prevent the laying of eggs.
- Plow in the
fall to expose the larvae or deeply bury the pupae. - Cultivate
fields in the spring after vegetation has appeared and grown a few
inches, then delay seeding to starve the cutworms. - Plan rotations
to avoid row or hill crops following a grassy sod. Plow sod fields
in late summer or early fall the year before planting. - Cultivate
frequently to injure and expose hiding cutworms to predators. - The construction
of ditches and dusty furrows may interrupt armyworms. - Place foil
or paper wraps or cardboard collars around transplants; extend a
few inches into the soil and several inches up the stem. - Dig in the
soil around damaged or adjacent plants in the row; find and destroy
the cutworm. - Plant a thick "trap crop" of sunflower,
a favored host, around the perimeter of the garden; find and
destroy attacking cutworms daily. - Use a tanglefoot
band on trees being attacked by climbing cutworms. - Other suggested
home remedies include catching and placing toads in the garden,
wrapping onion stems around the stems of transplants, placing a
ring of moist wood ashes around the plants, and placing a toothpick
or 16d nail alongside each transplant stem. Chemical treatments
are available as either homemade or commercial poison baits or as
insecticide treatments directed to the soil surface or on and around
the plants. Granular insecticide treatments, applied to protect
the seed and developing seedlings from soil insects, are of little,
if any, value in controlling cutworms. Adapted
from G.R Nielsen, University of Vermont Extension, 1999
Pesticides
are poisonous! Read and follow all safety precautions on labels.
Handle carefully and store in original containers out of reach
of children, pets or livestock. Dispose of empty containers
immediately, in a safe manner and place. Pesticides should never
be stored with foods or in areas where people eat.
When trade names are used for identification, no product endorsement
is implied, nor is discrimination intended against similar materials.
Be sure that the pesticide you intend to use is registered for
the state of use.
The user of this information assumes all risk for personal injury
or property damage.
For more
information, call the URI CE Gardening and Food Safety Hotline
at 1-800-448-1011 or (401)874-2929 from outside Rhode Island;
Monday-Thursday between 9 am and 2 pm.
University
of Rhode Island Cooperative Extension provides equal program
opportunities.
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