Совка кукурузная: описание и методы борьбы.

Species of moth

Helicoverpa zea, commonly known as the corn earworm, is a species (formerly in the genus Heliothis) in the family Noctuidae. The larva of the moth Helicoverpa zea is a major agricultural pest. Since it is polyphagous (feeds on many different plants) during the larval stage, the species has been given many different common names, including the cotton bollworm and the tomato fruitworm. It also consumes a wide variety of other crops. The species is widely distributed across the Americas with the exception of northern Canada and Alaska. It has become resistant to many pesticides, but can be controlled with integrated pest management techniques including deep ploughing, trap crops, chemical control using mineral oil, and biological controls. The species migrates seasonally, at night, and can be carried downwind up to 400 km. Pupae can make use of diapause to wait out adverse environmental conditions, especially at high latitudes and in drought.

The corn earworm is found in temperate and tropical regions of North America, with the exception of northern Canada and Alaska as it cannot overwinter in these areas. Cotton earworms have also been reported from China in 2002. The taxonomy of Helicoverpa was poorly understood for a long time. Many older works referring to "Heliothis obsoleta", a synonym of H. armigera, are actually about H. zea.

Eggs are individually deposited on leaf hairs and corn silks (not in reference given). They hatch after 66 to 72 hours of development.

Following hatching, larvae feed on the reproductive structures of the plant and usually develop through four to six instars. Through maturation, older larvae become aggressive and cannibalistic, leaving one or two larvae per feeding site (See Interfamilial Predation). They usually have orange heads, black thorax plates, and a body color that is primarily black. Mature larvae migrate to the soil, where they pupate for 12 to 16 days.

Larvae pupate 5 to 10 cm below the soil surface.

Adults have forewings that are yellowish brown in color and have a dark spot located in the center of their body. Adult moths collect nectar or other plant exudates from a large number of plants, and live for 12 to 16 days. Females can lay up to 2,500 eggs in their lifetime. H. zea is the second most important economic pest species in North America, next to the codling moth.

Two kinds of control measures have been advocated since the 19th century. Pesticides are one method by which corn earworm populations are controlled; however, since they have been widely used, the insects have become resistant to many pesticides. Strains of maize have been genetically modified to produce the same toxin as the bacterium, and are referred to as Bt corn.

More than 100 insect species prey on H. zea, usually feeding on eggs and larvae. Some plants emit a blend of chemicals in response to damage from H. zea, which attract parasitic insects. When the wasps find damaged host plants, they hover around and then search for the host with their antennae. When the females find their prey, they use their antennae to position themselves and deposit eggs into the host. Migration of 400 km is common for such flights as moths are carried downwind. Most activity is restricted to the night time. By preparing themselves for a major change in environmental conditions, they can increase reproductive success.

Helicoverpa zea has a wide host range, attacking vegetables that include corn, tomato, artichoke, asparagus, cabbage, cantaloupe, collards, cowpea, cucumber, eggplant, lettuce, lima bean, melon, okra, pea, pepper, potato, pumpkin, snap bean, spinach, squash, sweet potato, and watermelon. Various signs reveal the presence of these moths.

Helicoverpa zea earns its nickname the corn earworm for its widely known destruction of cornfields.

Helicoverpa zea is the most common and destructive pest of soybean growth in Virginia.

A hormone produced in the brain of the female moths controls sex pheromones. The hormone is released into the hemolymph to stimulate pheromone production. Pheromone biosynthesis activating neuropeptide (PBAN) is a peptide that regulates pheromone production in moths. It acts on the pheromone gland cells using calcium and cyclic AMP. Although the photoperiod regulates the release of PBAN to some extent, the chemical signals from the host plant supersede the effect from the time of day. Female moths often become depleted of sex pheromone after mating within 2 hours of separation from the male. The pheromonostatic peptide (PSP), a protein 57 amino acids long found in the male accessory gland, is what causes depletion of the female's sex pheromone. This capability in males has been selected for because it increases the reproductive fitness of those that carry it, since other males will not be attracted to a female without a sex pheromone; thus, the female will bear only the first male's offspring. When females are infected with the virus Helicoverpa zea nudivirus 2, they produce 5 to 7 times the amount of sex pheromone than uninfected females.

Sperm competition and chemicals introduced to females through mating have a negative effect on females and their lifespan.

Males must first wait to sense a female's pheromones before they can locate her.