Using fertilizer to control crop pests
　　 1. Nitrogen fertilizer: commonly used nitrogen fertilizers, such as urea, ammonium bicarbonate, ammonia water, etc., have the effects of stimulation, corrosion and fumigation on pests, and are used to control pests such as aphids and spider mites, which have small body size and weak endurance. When pests, with 2% urea solution or spraying the outer root 1% ammonium bicarbonate solution, spray once every 7 days 2 - 3 times, with good control effect.
　　 2. Phosphate fertilizer: Spraying phosphate fertilizer on tomato, corn and cotton can control green insects and cotton bollworms.
　　 3. Potassium fertilizer: use 10kg of grass ash to 50kg of water , soak for one night and night, spray with filtrate to control aphids.
　　 4. Calcium fertilizer: 30--40kg of silicon and calcium fertilizer per 667 square meters of corn and soybean can avoid the damage of corn borer and bean pod; 20--30kg per 667 square meters of wheat can reduce the damage of armyworm. In addition, spraying with 1 % urea plus 1 % dichlorvos can kill red spiders, aphids and other pests on vegetables.
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