To put it simply, there are the following reasons:

1. The environmental conditions in the invasive area are suitable for the survival of pests, and at the same time there is a lack of natural enemies that restrict pests. For example, hairy crabs are a delicacy on the table in China, but they broke out in Germany.

The same is true of Hyphantria cunea, which was restricted by natural enemies in its origin, but it disappeared after it was introduced to China, so the insect population only increased rather than decreased. Later, entomologists in China found a natural enemy of the American white moth, the Zhou's biting wasp, which has been put into control application.

2. The American white moth has strong reproductive ability and strong survival ability. A female moth can lay about 1 eggs once mating, and the height can reach 2. A large-scale prevention and control, unless all extinct, as long as a few live, after a year or two can be a disaster. Moreover, the American white moth has a variety of feeding habits, and almost all afforestation trees and greening trees can feed, which makes people hard to prevent.

3. limitation of control method. If it happens in urban areas and residential areas, chemical pesticides harmful to people and animals and the environment cannot be used. Moreover, when feeding on trees, the control effect is naturally poor because it is relatively high, and the drug spraying is not so high.

chemical control

was used in the outbreak of Hyphantria cunea. The first generation larval stage from May to June every year is the key period of chemical control. The insecticides with high activity to larvae are bifenthrin, beta-cypermethrin, beta-cypermethrin and fenpropathrin.

Before the larvae break the net, use 4.5% beta-cypermethrin+emamectin benzoate to dilute it by 1 times. After the larvae break the net, they can spray 15-2 times of pyrethroid pesticides such as deltamethrin on the crown, which has good control effect.

Physical control

Using the phototaxis of the adult Hyphantria cunea, the adults were trapped and killed by black light to reduce mating and oviposition. In the adult stage, the insecticidal lamp is hung at a height of 2-3 meters above the ground, and the lamp is turned on every day from 19: to 6: the next day to trap and kill the American moth adults.