|Corn Earworm Moth - Heliothis zea / Helicoverpa Zea|
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Family: Noctuidae. Larvae are variously known as as corn earworm, cotton bollworm or tomato fruitworm. Live adult moths photographed at Winfield, Illinois.
Corn earworm is found throughout North America except for northern Canada and Alaska. In the eastern United States, corn earworm does not normally overwinter successfully in the northern states. It is known to survive as far north as about 40 degrees north latitude, or about Kansas, Ohio, Virginia, and southern New Jersey, dependingon the severity of winter weather. However, it is highly dispersive, and routinely spreads from southern states into northern states andCanada. Thus, areas have overwintering, both overwintering and immigrant, or immigrant populations, depending on location and weather. In the relatively mild Pacific Northwest, corn earworm canoverwinter at least as far north as southern Washington.
This species is active throughout the year in tropical and subtropical climates, but becomes progressively more restricted to the summer months with increasing latitude. In northeastern states dispersing adults may arrive asearly as May or as late as August due to the vagaries associated with weather; thus, theirpopulation biology is variable. The number of generations is usually reported to be one in northern areas such as most of Canada, Minnesota, and western New York; two in northeastern states; two to three in Maryland; three in the central Great Plains; and northern California; four to five in Louisiana and southern California; and perhaps seven in southernFlorida and southern Texas. The life cycle can be completed in about 30 days.
Corn earworm has a wide host range; hence, it is also known as "tomato fruitworm," "sorghum headworm," "vetchworm," and "cotton bollworm." In addition to corn and tomato, perhaps its most favored vegetable hosts, corn earworm also attacks artichoke, asparagus, cabbage, cantaloupe, collard, cowpea, cucumber, eggplant, lettuce, lima bean, melon, okra, pea, pepper, potato, pumpkin, snap bean, spinach, squash, sweet potato, and watermelon. Not all are good hosts, however. Harding (1976a), for example, studied relative suitability of crops and weeds in Texas, and reported that although corn and lettuce were excellent larval hosts, tomato was merely a good host, and broccoli and cantaloupe were poor. Other crops injured by corn earworm include alfalfa, clover, cotton, flax, oat, millet, rice, sorghum, soybean, sugarcane, sunflower, tobacco, vetch, and wheat. Among field crops, sorghum is particularly favored. Cotton is frequently reported to be injured, but this generally occurs only after more preferred crops have matured.
Fruit and ornamental plants may be attacked, including ripening avocado, grape, peaches, pear, plum, raspberry, strawberry, carnation, geranium, gladiolus, nasturtium, rose, snapdragon, and zinnia. In studies conducted in Florida, Martin et al. (1976a) found corn earworm larvae on all 17 vegetable and field crops studied, but corn and sorghum were most favored. In cage tests earworm moths preferred to oviposit on tomato over a selection of several other vegetables that did not include corn.
Order Lepidoptera: Moths. Unlike the butterflies, moths are usually nocturnal. Many moths and their caterpillars are major agricultural pests in large parts of the world. Moths in the family Tineidae are commonly regarded as pests because their larvae eat fabrics, clothes and blankets made from natural fibers such as wool or silk. Moths in the genus Farinalis feed on stored grain, flour, corn meal and other milled grain products.
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