Control techniques of Helicoverpa armigera

Cotton bollworm (Helicoverpa armigera) is a major pest in cotton bud and boll stage. it is one of the insects of the genus Helicoverpa armigera, which is widely distributed in China and all over the world. Cotton areas in the Yellow River valley and the Yangtze River valley have suffered more seriously. In recent years, cotton areas have also occurred from time to time. Let's take a look at the control techniques of cotton bollworm.

Hazard characteristics

Cotton bollworm (Helicoverpa armigera) is an important boring pest in cotton bud and boll stage, which mainly eats buds, flowers, bolls and tender leaves. The adults hide in the back of the leaves during the day, begin to move at dusk, feed on nectar, have phototaxis, and the eggs are scattered in the upper part of the cotton plant. The first instar larvae feed on tender leaves, followed by harmful buds, flowers and bolls, which mostly eat buds and bolls from the base, and can transfer the damage. The bracts of the injured young buds open and fall off, and the eaten green bolls are easy to be contaminated and rot. The larvae have the habit of harmful transformation, and the transfer time is mostly in the night and early morning, when the pesticide is easy to come into contact with the insect body, and the control effect is the best.

Occurrence regularity

Cotton bollworm occurs 3-4 generations a year in the cotton area of the Yellow River basin and 4-5 generations a year in the cotton area of the Yangtze River basin, overwintering as diapause pupae in the soil. The first generation mainly harms the wheat field, the second generation larvae mainly harm the top of cotton, and the third and fourth generation larvae mainly harm the buds, flowers and bolls of cotton, resulting in a large number of shedding of damaged buds, flowers and bolls, which has a great impact on cotton yield. In addition to harming cotton, the 4th and 5th generation larvae sometimes become the main pests on crops such as corn, peanuts, legumes, vegetables and fruit trees.

Reproductive habit

Helicoverpa armigera occurs for 6 generations a year in South China, overwintering as pupae in the soil near the host rhizosphere, and then Eclosion and oviposition in the following spring. The first generation is mostly harmful to crops such as tomatoes and peas. After the second generation, there is generation overlap in the field. Adults perch on the back of leaves or shade during the day, and begin to move at dusk, absorbing plant nectar as supplementary nutrition, strong flying ability, phototaxis, and strong tenderness when spawning. The eggs are scattered in the tender leaves and fruit stalks of the host, and each female generally lays more than 900eggs, up to a maximum of more than 5000. The newly hatched larvae did not eat and move on the back of the leaves on the same day, and moved to the growth point on the second day, but the damage was not obvious. On the third day, they became the second instar and began to eat flowers, twigs, buds and fruits. The stage of overeating occurs after 4 years old. The mature larvae were pupated in the soil chamber at a depth of 5cm to 15cm.

Prevention and control technology

1. Autumn ploughing and winter irrigation: autumn ploughing and winter irrigation can depress the overwintering insect population, cotton, corn, tomato and other fields seriously damaged by cotton bollworm in autumn, carry out autumn ploughing and winter irrigation and break the ridge of the field, destroy the overwintering place, increase the overwintering mortality rate, and reduce the occurrence of the first generation.

2. Artificial catching of insects: making use of the habit that adults of cotton bollworm like to perch and lay eggs in the trumpet mouth of corn, special people beat heart leaves every morning to eliminate adults, reduce insect sources, reduce the use of chemical pesticides, protect natural enemies, and improve the ecology of cotton fields.

3. Strengthen the management: properly control the irrigation in the later stage, control the amount of nitrogen fertilizer, prevent the overgrowth of cotton, and reduce the harm of cotton bollworm. Foliar spraying of 2% superphosphate leaching solution during the spawning period of adult cotton bollworm not only has the effect of foliar fertilization, but also can reduce the fecundity of cotton bollworm in cotton field. Timely topping and pruning and taking the branches and leaves out of the field for destruction can eliminate the eggs and larvae of cotton bollworm and reduce the occurrence of cotton bollworm in cotton field.

4. Poplar branch trapping: making use of the characteristics of cotton bollworm adults' tendency to poplar leaf volatiles and hiding in poplar branches during the day, placing poplar branches to trap moths in cotton fields is an effective method during adult Eclosion and oviposition. Put 6 to 8 per mu and catch moths and pinch them before sunrise. High pressure mercury lamp and frequency vibrating insecticidal lamp have the characteristics of trapping and killing a large number of cotton bollworm and little killing to natural enemies, so it is suitable to be used in cotton bollworm reoccurrence area and Eclosion peak period.

5. Pesticide control: the control of cotton bollworm should be mainly biological pesticides or pesticides with little damage to natural enemies. The second generation cotton bollworm should be controlled by 20% methomyl EC 1500 times. The third and fourth generation cotton bollworm should be sprayed with 48% chlorpyrifos EC 50 60 ml per mu to 50 60 kg water. During the control period of the third and fourth generation cotton bollworm, the cotton plant is tall and the spawning is scattered. Spraying should be controlled from the peak egg incubation period to the young larva stage. Cotton leaves front and back, top, flowers, buds, bolls evenly applied to ensure efficacy, at the same time pay attention to alternate use and rotation of drugs, timely supplementary spraying in case of rain after application.