What are the black spots on the leaves?

Prevention and control methods:

(1) give priority to prevention. When buying bluegrass, carefully observe whether there are scale insects in the seedlings. Secondly, because scale insects are the most harmful from May to September, they are most likely to occur in the environment where orchids are too humid, stuffy and poorly ventilated. Therefore, daily management should pay special attention to environmental ventilation to avoid excessive humidity.

(2) When there are a few scale insects, you can manually remove them with brushes, soft-haired toothbrushes and toothpicks. , and then rinse with water.

(3) When using drugs to control nymph, it should be done when nymph has not formed wax shell for a long time. The pesticide used can be 40% dimethoate or omethoate emulsion 1000 times, quick killing 1000 times, assassination 500-800 times or "Kang Hua 1". In addition, we should pay special attention to the fact that scale insects are prone to drug resistance, so we should master the concentration of pesticides and use pesticides alternately.