Apple growers sometimes find that the branches of the apple tree are covered with white cotton wool, and many growers will think that the apple tree has some kind of disease, so they look around for ways to treat it. But no matter what treatment is used, there is no effect. Recently, through consulting with fruit tree experts, I learned that these white cotton flocculent things are not apple diseases, but an insect pest from the United States, and it is certainly ineffective to treat this insect pest with disease prevention methods.
So, what kind of insect pest is this?
This pest is the apple cotton aphid infestation, because the apple cotton aphid is a white aphid, so it looks like the branches of the apple tree are covered with white cotton wool from a distance.
This apple cotton aphid first occurred in the United States, and later, with the spread of apple seedlings to the world, it harmed apple trees at the same time, but also endangered trees such as wattles, begonias, and bonuses. Once the fruit tree is damaged, the adult and nymphs of the apple cotton aphid will parasitize on the branches of the fruit tree, frantically sucking the branches wounds, new shoots, leaf axils, fruit puddles and exposed sap in the root system of the fruit tree, so that the victim cortex will swell into tumors, and finally cause other diseases.
According to the observation of fruit farmers, after the occurrence of cotton aphid infestation in apple trees, the part of the branch is first swollen, and after about one or two months, a small tumor is gradually formed, and, over time, the tumor will slowly increase; if the petiole encounters harm, the victim part slowly becomes black-brown, and the leaves will fall off early; if the lateral root encounters harm, the injured part will form a tumor, and the part that forms the tumor will not be able to grow the whisker root, and gradually decay, seriously affecting the absorption of water and fertilizer by the lateral root, and finally leading to the weakening of the tree. Shortened lifespan, few results, small fruit, poor coloring; if the fruit encounters harm, there will be a phenomenon of stunted fruit, and it is easy to fall off.
In general, apple cotton aphids mostly occur in the high temperature season from June to July, and this is also the peak of the annual breeding of apple cotton aphids, if there is more rain at this time, it will accelerate its intergenerational reproduction, if it is not prevented in time at this time, its number will multiply, and produce a small number of winged aphids to the surrounding trees, quickly spreading from a tree to the surrounding area and even the whole garden. However, due to the high temperature in July and August, its breeding rate will slow down, but in September and November, as the temperature decreases, the apple cotton aphid will have a second breeding peak, resulting in white "cotton wool" hanging on the branches.
So, how to control apple cotton aphids?
1. Combine pruning to prune insect branches
In the winter pruning, it is necessary to cut off and burn the branches where the insect infestation is more serious, at the same time, scrape the old warp skin at the branch and the saw mouth, clean up the insect scars, and take the scraped residue out of the garden to burn or bury deeply, completely eliminating the living environment of apple cotton aphids.
2. Root administration
Every winter, 10% imidacloprid wettable powder 2000 times liquid can be used to irrigate the roots, the amount of irrigation of the liquid should depend on the size of the apple tree, generally the potion penetrates into the root part. Before irrigating the roots, the soil around the roots should be shaved open, and then covered with soil after irrigation. This effectively kills the apple cotton aphids that parasitize the roots.
3. Canopy spraying
In June-July, the canopy can be sprayed with 48% chlorpyrifos emulsion 1500 times liquid, 10% imidacloprid wettable powder 4000 times liquid, 3% acetamidine emulsion 2000 times liquid, and sprayed again after 7 days. In the spray should be uniform, thoughtful, meticulous, in order to improve the efficacy, silicone can be added to the liquid. In addition, when spraying, attention should be paid to the safe interval between apple picking to prevent drug damage.
4. Protect and utilize natural enemies
The natural enemies of apple cotton aphid include aphid wasps, seven-star ladybirds, turtle pattern ladybirds, heterochromatic ladybirds, etc., among which aphid wasps have a long occurrence period, fast reproduction and the strongest control ability. Spraying of broad-spectrum tactile chemical insecticides should be prohibited during periods of high natural enemies.