Armyworms are Poised
Tim Gibb and Doug Richmond, Department of Entomology,
We have been monitoring reports of very large infestations
of armyworm moths flying into Kentucky this spring. Armyworms move
north with storms from the southern states each year and depending
upon how and where the storms blow, will dictate when and how many
moths we have to deal with. Fortunately, in Indiana we have not
seen the huge numbers of moths that Kentucky reported earlier this
spring, however, we do have our fair share. The moths that have
come our way have already laid eggs (normally in grassy vegetation
such as in ditch banks, vacant lots, or in agricultural areas such
as wheat, grass hay, and grass cover crops). This is important
for turfgrass managers because when these grasses mature and dry
down, armyworms leave them and often find their way to the green,
succulent turfgrasses that we manage. Wheat is maturing very quickly
right now and we are already hearing reports of armyworms moving
into adjacent golf courses or residential neighborhoods.
If armyworms are detected migrating from border areas or fields,
spot/perimeter treatments in these areas are recommended. These
are only effective, however, if the migration is identified early
Mature fall armyworms measure 1.5 inches long with
a body color that ranges from green to brown or black with distinct
longitudinal stripes on their body. They can be distinguished from
similar caterpillars by the presence of a prominent inverted white "y" on
Armyworm feeding usually is from the margins of the leaf toward
the midrib. This gives turfgrass a ragged appearance. When infestations
are high, most of the plant may be consumed.
Preventive insecticide treatments are not warranted
because outbreaks are so sporadic and mortality due to natural
causes is usually high. The key to controlling fall armyworm
is early detection because infestations of fully mature larvae
feed voraciously and can very quickly damage turfgrass.
Thresholds are not well developed for fall
armyworm in turfgrass, but we suggest treatment when average
counts reach two or three ½-inch
larvae per square foot.
Any product labeled for caterpillar control in turf also should
be effective for fall armyworm control. Be sure to apply
insecticides only when periods of dry weather are expected so that
the insecticide is not washed off of the leaves.
Several biorational controls such as Bacillus
kurstaki, Steinernema glaseri or Heterorhabditis bacteriophora nematodes, or spinosad can be effective on armyworms, however,
because of the large size of the migrating worms and the amount
of damage they can do in a short time frame, most turfgrass managers
prefer a more fast acting solution such as with conventional insecticides
containing acephate, bifenthrin, carbaryl, cyfluthrin, lambda-cyhalothrin,
trichlorfon, permethrin or others.
Click image to enlarge
Armyworm Infested Turf (Photo by Doug Akers)