Egg - Eggs of both species are very similar in appearance -- subspherical with a flattened base, about 0.6 mm in diameter, and white or cream in color. They develop a reddish-brown band just prior to hatching.
Larva - Both species are similar in appearance. About 1.5 mm long, newly emerged larvae are yellowish-white with brown heads. With pale stripes running lengthwise on the body, fully developed larvae may be basically greenish-yellow, reddish-brown, or even black. Such larvae may be up to 44 mm long.
Pupa - Shiny and reddish-brown at first, the pupae become dark brown before adult emergence.
In North Carolina, budworms occur throughout the state but are generally more severe in the southern Coastal Plain. Some early transplanted fields in heavily infested areas have had as many as 100 percent of plants infested.
Host Plants - Tobacco, cotton, and soybeans are the only cultivated crop hosts of the tobacco budworm in North Carolina. The corn earworm feeds on at least 16 cultivated plants. Tobacco is the most important host of the tobacco budworm; whereas, corn is the most important host of the corn earworm. The tobacco budworm does not infest corn, but both species are found on cotton and soybeans. Wild hosts of the tobacco budworm include deergrass and toadflax.
Damage - Budworms, primarily the tobacco budworm, are important pests of flue-cured tobacco in North Carolina. Both species feed on tobacco leaves, but such feeding causes little appreciable damage. Damage is most serious when feeding is in the vegetative bud of the plant. The larvae often cause distorted leaves by feeding upon the tips of the leaves in the developing bud. Large holes develop from earlier feeding as the leaf tissue expands. Plants prematurely topped by budworm feeding produce profuse sucker growth. Both species of caterpillars may also bore in stalks or midribs.
Life History - Budworms overwinter as pupae in the top 5-10 cm (2-4 in) of soil. Tobacco budworm adults emerge in North Carolina from late April to mid-May. Corn earworm adults emerge from early May to early June. Females generally emerge earlier than males.
Eggs are deposited on the leaves or buds of the tobacco plant. After hatching, larvae may first feed on the leaf and then move to the bud region. Tobacco budworm larvae have five or six instars with the development period varying from 21 to 25 days. Corn earworm development is similar.
Pupation occurs in the soil. Tobacco budworm pupae enter diapause in September in North Carolina and corn earworms begin diapause in August. Both species have four generations in North Carolina.
Topping plants, good sucker control, stalk destruction after harvest, and fall and winter plowing are all important cultural control practices to reduce diapausing populations. Budworms are difficult to control on tobacco prior to flowering because most of the larvae are hidden in the vegetative bud where it is difficult for insecticides to reach.
A number of insecticides, however, are available to control budworms. The economic threshold level for these pests is reached when five or more plants out of 50 are infested with budworms of any size prior to buttoning. Budworms will not cause loss of any importance after the plant has buttoned. For specific control recommendations, consult the current North Carolina Agricultural Chemicals Manual.