Corn Armyworm Control Tips

Today I will tell you about the prevention and control methods of corn armyworms. If you take a good look at the problems you encounter, you can solve them:

1. Types of crops endangered:

In our city, it mainly harms autumn crops such as corn and sorghum. It is the most serious migratory pest on cereal crops in my country. Except for Xinjiang, it is distributed in other provinces and regions. When it is serious, it often eats up all the corn seedlings overnight, resulting in missing seedlings and broken ridges, and even plowing and replanting.

(II) Habits and patterns of occurrence of harm:

Adults hide during the day and come out at night. They lay eggs mostly in the yellowed tips and leaf sheaths of the middle and lower parts of wheat. A single female lays 1,000 to 2,000 eggs. Adults have a strong tendency to sweet and sour liquid and black light. Larvae are mostly active in the morning and evening, that is, from sunrise to 10 o'clock in the morning and around dusk. They like to eat gramineous crops and weeds. Their appetite increases with age. The fifth to sixth instars are the gluttonous stage. They are characterized by group damage, gluttony, and omnivorous. Larvae often migrate in groups to cause damage, so they are also called "army bugs." The first and second instar larvae only eat the leaf flesh to form skylights. After the third instar, they eat along the leaf margins to form notches. When the damage is serious, they eat up most of the leaves, leaving only a very short midrib. When frightened, the larvae have the habit of pretending to be dead and diving into the soil.

In our area, armyworms have three generations a year, and the second generation mainly harms summer corn. Since armyworms cannot overwinter in any stage north of 33 degrees north latitude, the large number of adults that appear in our city in spring migrate from the south.

The armyworm is a pest that prefers humidity and is afraid of high temperature and drought. However, when there is too much rainfall, especially when there is a heavy rain or storm, the number of armyworms often decreases significantly. The optimum temperature for armyworms to lay eggs is generally 19-22℃, and the suitable field relative humidity is above 75%. When the temperature is below 15℃ or above 25℃, the number of eggs laid is significantly reduced. In the case of high temperature and low humidity, the number of eggs laid will be even less. The larvae are not resistant to high temperature and low humidity. The temperature is 19-23℃ and the relative humidity is 50%-80% most favorable. When the temperature is as high as 35℃ or the relative humidity drops to 18%, the newly hatched larvae cannot survive. Generally, irrigated fields, fields with dense planting of previous wheat, fields sown between wheat ridges, and fields with a long symbiotic period of wheat and corn are conducive to the laying of eggs by adults and the growth and development of larvae due to sufficient food sources, suitable temperature and humidity, and the insect population density in the field is large, and the damage is relatively serious.

3. Relationship between occurrence and environment:

There are many environmental factors that affect the occurrence of armyworms, mainly climate, food nutrition, natural enemies and agricultural production activities. When a large outbreak occurs, they have the habit of migrating in groups due to food shortage or unsuitable environment. Rainfall and temperature and humidity changes are important factors affecting the occurrence of armyworms. Warm and humid conditions with abundant grass plants are conducive to the occurrence of armyworms; fields with good water and fertilizer conditions and dense growth are prone to insect pests; drought or continuous rain is not conducive to its occurrence.

(IV) Prevention and control techniques

1. Agricultural prevention and control: For fields with hard stubble, shallow tillage should be carried out in time after the corn seedlings emerge to destroy the habitat of corn borers and reduce the insect source.

2. Manual killing: After the corn seedlings emerge, the larvae are killed manually by pinching them in the morning and evening when they feed.

3. Chemical control:

(1) Killing with poison bait: Add 100 g of 90% dichlorodiphenyltrichloroethane to an appropriate amount of water per mu, mix it with 1.5 kg of fried bran to make poison bait, and spread it along the corn rows in the evening to kill the pigs.

(2) Foliar spray: Use 20-30 ml of 2.5% dimethoate, 2.5% Gongfu emulsifiable concentrate or 4.5% highly effective cypermethrin diluted with 30 kg of water and spray evenly per mu; spray 1500 times diluted carbofuran No. 3 on the leaves.

(3) Spread poisonous soil: Use 75-100 g of 40% phoxim emulsifiable concentrate per mu, add appropriate amount of water, mix with 40-50 kg of sand and soil, and spread on the heart leaves of corn. This can protect natural enemies and prevent corn borers at the same time.

In the process of preventing and controlling corn armyworms, it is necessary to keep abreast of the insect monitoring and early warning information issued by the local plant protection department, so as to achieve early detection and early prevention, and try to prevent and control corn armyworms before the third instar. The prevention and control time is generally selected in the morning and evening when the larvae are most likely to feed; the spraying site should be applied on the heart leaves of corn as much as possible.