There are five species of aphids that have been found on cotton: cotton aphid, cotton tuber, amaranth, callus, and kidney beans.
Among them, cotton aphid is the main pest and is one of the important pests on cotton in China. The Yellow River Basin and the Liao River Basin cotton area is the most serious damage, followed by the Yangtze River Basin cotton area.
Damage symptoms
The cotton aphid is inserted into the back or tender part of the cotton leaf with a sucking mouth sucker, sucking juice, and the affected leaf is curled to the back, and the leaves have honeydew excreted by the aphids, which often breeds mold. After the cotton was damaged, the plants were dwarf, the leaves became smaller, the number of leaves decreased, and the buds and the bells were reduced.
Habits
Cotton aphids occur in the south of China's cotton district for 20 to 30 generations a year, and northern cotton fields occur for 10 to 20 generations a year. In most parts of the country, cotton aphids use eggs to winterize on the four wintering hosts of hibiscus, pomegranate, pepper, and holly. . There are fins and wingless pupa in cotton aphids. The main causes of winged pupa are: 1 population crowding; 2 nutrient deterioration; 3 climate conditions are not suitable; 4 transfer between winter host and Joe's home.
The migration of cotton aphids is regular, and they can be divided into three types from the different characteristics of the migration: 1 The host moves to the summer host from the wintering host; 2 The host moves between the summer hosts; 3 The host moves from the summer host to the wintering host. Winged owl has a yellowish habit.
Cotton aphids damaged in the cotton fields are divided into seedlings and Fuxi. The emergence of seedlings from seedlings to budding is suitable for low temperatures. When the temperature exceeds 27°C, reproduction is inhibited, and the population rapidly declines. Fumonium mainly occurs in late July to August, and is suitable for high temperatures, at 17～ At 28°C, large populations of insects began to rapidly decline when the average temperature was above 30°C.
The optimum temperature for cotton aphids is 25°C and the relative humidity is 55% to 85%. Rainy weather is not conducive to aphids. Heavy rain has a significant inhibitory effect on aphids, and when it is sunny, rain, cloudy days, and drizzle are favorable for them. Topography and landforms have a great impact on the migration of locusts. In the event of obstacles, they will easily form a center of occurrence and cause serious damage. In general, single cotton fields occur early and heavy, while interplanting cotton fields occurs later. The nutritional conditions of cotton plants have an impact on the occurrence of aphids. Cotton plants with high nitrogen content have serious damage to aphids. In addition, natural enemies of cotton aphids can effectively control their damage. When the total number of enemies and the number of pupae is 1:40, they can basically be controlled.
Control methods
The prevention and control of cotton aphids is mainly based on agricultural control and biological control, supplemented by chemical control.
1. Agricultural control
(1) Planting insect-resistant varieties is an effective measure to control cotton aphids, such as planting 372 and so on.
(2) Intercropping can increase the types and number of natural enemies and control the locust infestation. Such as cotton and wheat intercropping; cotton and mung bean, green manure and other intercropping; planting corn, rape, sorghum and other crops to attract crops.
(3) The rotation of paddy crops can reduce the occurrence of cotton aphid. Where conditions permit, cotton and rice rotations are implemented.
(4) Deal with wintering hosts to reduce the source of early spring. Generally before and after the emergence of cotton seedlings, weeds inside and outside the cotton fields are removed. It is possible to treat the wintering host of pepper, pomegranate, hibiscus and holly overwintering, and reduce the amount of cotton in the field.
2. Chemical control
(1) Seed dressing
Before sowing, the amount of seeds per mu should be 1.5 to 2 kg with 3% carbofuran granules before sowing, mixing evenly, or using iron quercec (also known as aldicarb) for seed dressing, with an effective ingredient of 50 grams per mu, which can control pods. 40 to 50 days. The use of 3911 (pivotal) emulsion or granules, seed dressing seed dressing, the effect is also very good.
(2) Controlling aphids by dropping hearts and smearing
Use 40% omethoate emulsion or 40% monocrotophos or 50% methamidophos emulsion to dilute 80 to 100 times. Drop the drug on the top of the cotton seedling with a sprayer to control the damage.
Use a 40% omethoate emulsion or 40% monocrotophos or 50% methamidophos emulsion, polyvinyl alcohol, and water to prepare a smearing agent in a ratio of 1:0.1:5. Use a brush-like device to coat the solution. In the purple and green alternate parts of cotton stems, the effect of anti-worm insects can reach more than 90%.
(3) Spray control
Diluted 1000-1500 times spray with 50% monocrotophos, 50% phoxim, 40% omethoate, 40% chlorin, 35% miticide, 50% phosphine and other agents.
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