Control methods of corn armyworm

Corn armyworm, a major pest in the process of corn production, does great harm to corn. When it occurs seriously, it often eats up the corn seedlings overnight, resulting in lack of seedlings, broken ridges, or even ploughing and replanting. At present, it has begun to occur in some corn and millet fields in Changzhi County, and farmers should go deep into the field and control it in time.

I. occurrence and harm habits and rules

The adults lay eggs in the withered and yellow leaf tips and leaf sheaths in the middle and lower parts of wheat, and a single female laid 1000 li 2000 eggs. Adults have strong taxis to sweet and sour liquid and black light, and adults have strong flying ability and harmful characteristics of long-distance migration. The larvae are mostly active in the morning and evening, that is, before sunrise in the morning to 10:00 and before dusk. Armyworm is a moderately warm and humid insect, with the optimum temperature of 19: 23 ℃ and the optimum relative humidity of 50-80%. Like to eat Gramineae crops and weeds, food intake increases age by age, the fifth to sixth instar is overeating stage, with the characteristics of cluster harm, overeating, omnivorous, larvae often cluster migration harm, so it is also known as "marching insect". The first and second instar larvae only eat the leaf flesh into a skylight, and after the third instar, they nibble along the leaf margin, and when the damage is serious, most of the leaves are eaten up, leaving only a very short midrib; the body color of the larvae varies with the instar, density and food, and the young larvae feed on tender leaves, the body color is green to grayish green, when the insect population density is large, the 4th instar larvae are black or grayish black, and the mature larvae are 38mm long and yellowish brown with a vertical shape of "eight". There are five longitudinal lines on the back of the body. The larvae have the habit of pretending to die and sneaking into the soil. In general, irrigated fields, fields with multi-fertilizer and close planting of wheat in previous crops and interplanting fields with long symbiotic period of wheat and corn are beneficial to adult oviposition and larval growth and development because of sufficient food sources and suitable temperature and humidity, so the field population density is high and the harm is relatively serious.

Second, prevention and control technology

1. Agricultural control: after maize emergence, shallow ploughing should be carried out in time to destroy the habitat environment of corn armyworm and reduce the source of insects.

2. Artificial killing: after the emergence of corn seedlings, the larvae are artificially killed sooner or later when the larvae feed.

3. Chemical control:

(1) poison bait: 90% trichlorfon 100 grams per mu mixed with the right amount of water, mixed on 1.5 kilograms of fried wheat bran to make poison bait, spread along the corn line in the evening to trap and kill.

(2) foliar spray: 4.5% cypermethrin 50 ml or 40% omethoate 50 ml plus 77% dichlorvos 25 ml with water 30 kg foliar spray; 4.5% cypermethrin 50 ml plus cypermethrin 50 ml with 30 kg water for foliar spray.

(3) spreading poisonous soil: add an appropriate amount of water with 40% phoxim EC 75-100 grams per mu, and spread 40-50 kilograms of sandy soil in the heart and leaves of corn, which can not only protect natural enemies, but also prevent corn borer in the process of corn armyworm control, try to control corn armyworm before the third instar. The control time generally chooses the high incidence time when the larvae feed in the morning and evening, and the spraying site is applied in the heart and leaves of corn as far as possible, pay attention to personal protection and strictly prevent the occurrence of poisoning accidents.