Symptoms and damage
attack many different kinds of plants. When food is scarce, they will move to
plants that are not normally attacked. Thus, armyworms can be found on nearly
any plant as they migrate in search of edible foliage. Besides warm-season
turfgrasses, plants attacked by armyworms include grain and forage sorghum,
corn, small grains, sweet potato, beans, turnip, clover, tobacco, spinach,
cucumber, potatoes, tomatoes, cowpeas, cabbage, bluegrass and others.
consists of foliage consumption. The small larvae will chew the green layer
from the leaves and leave a clearing or “window pane” effect. The first three
instars do very little feeding while the last two instars consume 85% of the
total foliage consumed.
COMMENTS on disease
and multiple natural enemies usually act together to keep populations under
control. Parasites such as wasps and flies are very effective against
armyworms. Predators, such as ground beetles, are also effective in limiting
outbreaks. Birds, skunks and rodents also consume large numbers of larvae and
pupae. Diseases such as insect viruses and fungi can also be important.
should be controlled when they occur in large numbers or plant damage is
becoming excessive. This will be apparent in turfgrass by examining the grass
blades. Damaged areas of lawns appear off-color and eventually turn brown as
damage progresses from small windowpane strips of damaged leaf tissue to
destruction of entire leaves. Armyworms feed any time of the day or night, but
are most active early in the morning or late in the evening.
with a labeled insecticide when leaf damage becomes evident and large numbers
of caterpillars are visible. Effective, low-impact insecticides include
halofenozide (small caterpillars only) and spinosad. Bacillus thuringiensis
(Bt) products are widely available and will selectively control small armyworm
larvae without harm to beneficial insects; however, Bt residues does not last
on turf for more than 1-2 days. Conventional insecticide choices for armyworms
in lawns include bifenthrin, carbaryl, esfenvalerate, permethrin and others.