① Different varieties: Different varieties have different degrees of falling flowers and fruits. Female flower varieties, in the case of poor pollination and fertilization conditions, will cause serious flower drop and fruit drop, or form seedless small fruits. Polyploid varieties, such as tetraploid varieties Jufeng and Heiaolin, sometimes have abnormal chromosome pairing, abnormal gamete formation and abnormal fertilization.

② Effects of nutritional conditions: Malnutrition, weak growth or excessive growth, and excessive plant load will all lead to falling flowers and fruits.

③ Environmental impact: If high temperature, drought, low temperature and rainy weather are encountered during flowering, it is not conducive to pollination and fertilization. Grape pollination and fertilization need suitable temperature and humidity. Too high or too low temperature is not conducive to flowering, pollination and fertilization. If the temperature exceeds 33℃, the pollen will lose its vitality. When the temperature is lower than 20℃, the flowering is slow and the pollen germination rate is low. Excessive humidity affects anther cracking and pollen spread; The humidity is too low (below 30%), and the stigma mucus is less, which affects pollen germination, makes fertilization poor, and causes flower drop and fruit drop.

(2) Measures to prevent falling flowers and fruits

In view of the causes of falling flowers and fruits, corresponding technical measures should be taken to prevent falling flowers and fruits.

① As far as variety selection is concerned, we should try our best to choose bisexual flower varieties with high self-pollination and seed setting rate. If female flower varieties must be used, attention should be paid to the allocation of pollination varieties to create good pollination conditions.

(2) For polyploid varieties with serious flower and fruit dropping, excessive growth should be avoided. For plants with vigorous growth, the fruiting branches can be picked before flowering, or growth retardants can be used to inhibit their growth, so as to prevent excessive flower and fruit drop.

(3) For poor management and poor vegetative growth of plants, we should first strengthen fertilizer and water management to make plants grow healthily; Secondly, to reduce the load of plants, we can properly thin some spikes or pinch the spikes to concentrate nutrition, which can effectively prevent falling flowers and fruits.

(4) In the greenhouse, create favorable conditions for pollination and fertilization, especially control the temperature and humidity of flowering period, and do not make it too high or too low.