Helicoverpa armigera is the main pest of cotton. In recent years, the resistance of cotton bollworm has been continuously enhanced, and the damage has become more and more serious. Especially in the case of rainy weather in August-September, the damage is even more rampant, generally causing cotton loss of more than 10%. How to improve the control effect of pesticides in cotton bollworms? Practice has proved that the following three points should be grasped in the prevention and control technology.
1. Use different spraying methods.
Due to the different emphasis of the hog hazards of various generations of cotton bollworms, different spray methods can be used to fully exert the effects of the medicaments. For example, in the second generation, 65% of the eggs are produced on the upper young leaves, and the focus of the spraying is on the upper branches and leaves of the cotton plants. The spraying method of "dot and circle" should be used to spray most of the liquid on the upper branches and leaves; The eggs of the 3rd and 4th generations of cotton bollworm are prolific in the top of the cotton plant, on the side of the heart and the surrounding young leaves. The focus of spraying is on these parts, and the spraying method of "four sides" should be adopted. The opportunity for the liquid to touch the insects and eggs is increased to improve the control effect. When using the medicine, please pay attention to the concentration of the liquid medicine, and do not increase it too much. The dosage should not be increased or decreased arbitrarily, so as not to cause damage to the cotton plant or reduce the control effect of the medicine.
2. Choose new pesticides that kill larvae and kill eggs.
In view of the spawning and dispersing of cotton bollworm, the egg period is only 3-4 days. If conventional pesticides such as dimethoate, parathion, and monocrotophos are used, it is difficult to control the damage of cotton bollworm. New pesticides that kill larvae and kill eggs must be used. According to our current situation, the effect is better: 10% chlorhexidine emulsion or 10% galvanic emulsion, 5-10 grams per acre, spray 50 kg of water, the control effect can reach more than 90%; or Use 15-20 grams of pyrethroid per acre or 20 grams of enemy to kill, add 25-30 grams of phoxim with better systemicity, 50 kg of water, mix and spray, the control effect can reach about 80%. The above pesticides should be used interchangeably to delay the development of pest resistance.
3, timely medication.
The eggs of cotton bollworm are scattered on the tender head, flower buds and young leaves of cotton. Therefore, from the beginning of cotton buds to September, a representative cotton field should be selected for spotted egg inspection. According to the egg after delivery, the first day of white, the second day The characteristics of black, brown on the third day, hatching on the fourth day, and the second day after hatching began to harm the cotton growth point. When the transfer began on the fourth day, there were 20-30 grains of cotton per 100 cotton plants. Take advantage of the timely use of drugs at 8-11 am or 3 pm. At the same time, during this period of time, it can also prevent the morning dew from diluting the liquid or reducing the effect with the dew.
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