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The Corn
Earworm (aka: tomato fruitworm, cotton bollworm) feeds
on crops including corn, tomato, cotton, green beans, clover, vetch,
lettuce, peppers, soybeans, and sorghum. Severe infestations of corn
earworm generally occur in the southern United States. Losses due to the corn
earworm in field corn have been estimated at 2.5% annually, with losses in the
southern United States ranging from 1.5 - 16.7%. Losses in sweet corn may be as
high as 50%.
Corn
earworm larvae vary greatly in color ranging from light green or pink to dark
brown or nearly black. Alternating light and dark stripes run the length of the
body. Double dark stripes can usually be seen down the center of the back, with the underside of the larva
typically light colored.
Adults are nocturnal moths about ¾ inch long, with a wingspan of 1½ inches. The
forewings are buff colored with dark lines or spots near the tips. In central to
northern regions, earworm infestations are a result of moth flights from
warmer climates, as most winters in the central - northern corn belt are too
severe to allow for overwintering. Eggs are laid singly on the leaves of
preferred food plants. Pubescent leaves are preferred, but corn tassels and
silks are even more attractive.
Injury
caused by the corn earworm ranges from destruction of the host crop to cosmetic
damage that may cause a crop to be unmarketable. The corn earworm feeds not only
on the whorl, tassel, and silks, but on the kernels of the ear itself. Severe
feeding on the leaves gives the plant a ragged appearance. Feeding on kernels at
the tip of the ear creates an avenue of entry for diseases, especially molds.
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