Cotton bollworm Helicoverpa armigera ( Hbn. )
(formerly known under the names Heliothis armigera and Chloridea obsoleta)
- The second most important pest of corn. Unlike the corn moth, the cotton bollworm shows a distinct tendency to feed on the reproductive organs of plants. Despite being omnivorous, in the conditions of Ukraine, corn serves as the main reserve for the pest.
Cotton scoop is a very variable species in terms of appearance and biological properties. The size and color of butterflies vary, the body length of which is 12-20 mm, and the wingspan is 30-40 mm. Front wings in females are orange-brown, in males they are lighter and usually greenish-gray [1]. The life span of an imago is usually within 20-40 days, the fecundity of a female is 500-1000 eggs (maximum up to 3000). The egg has a characteristic shape (0.4-0.6 mm in diameter), its surface is ribbed, the color is white at first, then greenish [2]. Eggs are laid one at a time, rarely 2-3 on leaves and reproductive organs of plants (threads of cobs, panicles) or on the downy part of the stem. The duration of development of cotton boll eggs in summer is 2-4 days, and in spring and autumn - 4-12 days. Caterpillars develop within 13-22 days, pass during this time 6 ages, reaching 35-40 mm in length in the last age. The color of cotton bollworm caterpillars varies from light green and yellow to red-brown [3]. Pupae of the cotton bollworm develop in the soil at a depth of 4-10 cm, less often in places where the caterpillars feed (on the ears of corn, sorghum panicles, etc.) for 10-15 days. Pupae hibernate in the soil. Their color varies from dark brown to reddish brown; length 15-20 mm.
Corn is one of the most desirable fodder plants for the cotton bollworm, but besides it, it damages many other species. Most often, the pest is found on tomatoes, sunflowers, soybeans, and among weeds - Theophrastus ropeweed, polynophyllous ambrosia, Schyrytsia zakinuta and other species.
Measures to combat the cotton bollworm include agrotechnical measures (weed destruction, deep plowing, inter-row treatments), chemical (treatment of plants with insecticides in the initial period of caterpillar development; it is important to keep in mind that older caterpillars are quite resistant to poisons), biological ( release of trichogram and use of biological preparations), sowing in optimal terms and cultivation of less damaged hybrids. Pheromone traps are used to monitor and signal the development of the pest.