Critical period for cotton summer aphid control

Aphids are divided into seedling aphids and summer aphids, which are two ecotypes of the cotton aphid that have differentiated to adapt to different environmental conditions. They mainly gather on the underside of cotton leaves or on tender tips to suck sap. In the cotton region of the Yellow River basin, summer aphids mainly occur from mid-July to mid-August, and can cause the upper tender leaves of cotton to curl and the middle leaves to become oily; in severe cases, they lead to shedding of squares and bolls. Because cotton has mostly closed its rows when summer aphids occur, with many leaves and dense branches, many farmers report that summer aphids are harder to prevent and control than seedling aphids.

1. Occurrence situation

Currently, cotton summer aphids are widespread in Hengshui City, and some fields have relatively severe damage. In Wuyi County, the number of aphids on three leaves per 100 plants is 3000-5000, with the highest exceeding 20,000, and severe leaf curling has already occurred; in Gucheng, the highest field had more than 10,000 aphids on three leaves per 100 plants, with a curled-leaf plant rate of 36%. The meteorological department predicts that in July our city will still maintain high-temperature weather, with precipitation close to normal. Hot, muggy weather with alternating sunshine and rain is favorable for the occurrence of cotton summer aphids. We remind farmers to closely strengthen field observation, apply pesticides scientifically and promptly, and minimize the yield loss caused by cotton aphids. The field chemical control methods for cotton aphids are provided below:

2. Control methods

1. Rotate the pesticides used. Rotate the use of conventional field pesticides such as acetamiprid, imidacloprid, and chlorpyrifos to reduce the likelihood of aphids developing resistance. Once aphids become resistant to a certain chemical pesticide, even if the number of applications is increased and the pesticide concentration is raised, the ideal control effect will not be achieved.

2. Spray the occurrence sites evenly and thoroughly. Cotton is now in full bloom, and the plants are tall, so when spraying, be sure to be careful and thorough, focusing on spraying the undersides of the middle and lower leaves of cotton, and strictly prevent missed spraying or missed application to truly ensure the quality of each spraying. Because aphids reproduce quickly, if one spraying is not thorough, many surviving aphids will remain, making the next control effort more difficult. Generally, the spray liquid volume is 50-60 kg per mu.

3. It is recommended to choose some new pesticides. For fields where conventional pesticides such as acetamiprid and imidacloprid have shown no obvious control effect, new-type pesticides such as 10% nitenpyram aqueous solution, 20% carbosulfan emulsifiable concentrate, or 10% clothianidin can be selected for control. Generally, 10% clothianidin wettable powder is used at 20 grams per mu, or 10% nitenpyram aqueous solution at 20 milliliters per mu.

4. The timing of pesticide application should be appropriate. During high-temperature periods, avoid noon and try to apply pesticides in the morning and evening, preferably before 10 a.m. and after 4 p.m. On the one hand, this can ensure personal safety, and on the other hand, it can avoid rapid evaporation and loss of the spray liquid caused by high temperatures, which reduces pesticide efficacy.