During the growth and development of fruit trees, a large number of fruit drops due to non-mechanical external forces, pests and diseases are called physiological fruit drops. It is observed that apple, pear, peach, grape and other fruit trees have two physiological fruit drops: the first time is two weeks after flowering, when the fruit expands rapidly and develops into young fruit; The second time occurs 2 ~ 4 weeks after the first fruit drop, which is usually called "fruit drop in June". Some fruit trees, such as apples, still have fruit drop before the fruit matures, which is called "fruit drop before harvest". Insufficient nutrition in trees and poor external environmental conditions are the main reasons for physiological fruit drop. The methods to prevent and reduce physiological fruit drop are as follows:

(1) Top dressing and water

Before the arrival of physiological fruit drop, topdressing nitrogen, phosphorus, potassium and other fertilizers under the tree 20 ~ 30 days in advance. The amount of fertilizer should be determined according to the needs of trees. For example, if the base fertilizer is sufficient, you can not chase it; Or spraying 0.3% ~ 0.5% urea and 0.5% potassium dihydrogen phosphate solution on the leaves for 2 ~ 3 times when the fruit is close to physiological fruit drop. At the same time, irrigation should be done in time after topdressing, which is conducive to exerting fertilizer efficiency as soon as possible.

(2) Planting green manure

Planting green manure such as Amorpha fruticosa, sweet clover and vetch in orchard can change soil structure, enhance soil permeability, improve soil fertility and prevent soil erosion. Reducing the harm of weeds is an effective measure to reduce physiological fruit drop.

(3) spraying hormones and trace elements

According to the practice, spraying 0.2% borax or 1000 times of vinegar essence at flowering stage can not only prevent flower falling, but also reduce young fruit falling after flowering. For fruit trees with physiological fruit drop, spraying 10 ~ 30μ l/L NAA solution in time one month before fruit harvest can reduce fruit drop, promote fruit coloring, increase hardness and improve storage resistance.

(4) prevent early defoliation

Leaves are the main organs that produce organic matter. Therefore, the key to the whole growth period is to protect the leaves. In order to prevent early defoliation, comprehensive control should be carried out. First of all, we should strengthen the management of soil, fertilizer and water to improve the disease resistance of fruit trees; Secondly, we should pay attention to clearing the garden to reduce the source of the first invasion; Third, strengthen prediction and timely and rational drug use. Generally, the Bordeaux mixture with the volume of 2000 times that of lime is sprayed for the first time in mid-April, and then sprayed every 20 days until the spraying is stopped 20 days before fruit picking. You can also spray 500 ~ 1000 times of carbendazim wettable powder, and the effect is good.