After the grapes bear fruit, the main management during this period is to strengthen fruit thinning, ear trimming, spraying, watering and fertilizing.

1. The purpose and function of thinning grape inflorescences and trimming fruit ears is to adjust yield, save nutrients, increase fruit setting rate and improve fruit quality. Thinning young fruits is carried out after physiological fruit drop. For large fruit varieties such as Kyoho, only about 50 fruits per ear can be left.

2. The growth of grapes requires a lot of water. Timely watering is required during several critical periods, such as after budding and before flowering; after fruit setting and during the fruit coloring period, and during drought. Moisture ditches should be cleaned promptly on rainy days to eliminate accumulated water.

3. Spray pesticides to reduce the occurrence of diseases. After spraying with pesticides, the grapes can be wrapped in bags to improve the quality of the grapes.

4. Fertilization is carried out at the early stage of fruit bearing, mainly nitrogen fertilizer, combined with phosphorus and potassium fertilizers. It not only promotes the enlargement of young fruits, but also facilitates the differentiation of flower buds. This stage is the peak growth period of grapes and a critical period that determines the yield of the second year. It is also called the "critical period of water and fertilizer".

Extended information

Causes of grape flower and fruit drop

1. Variety characteristics

For example, Kyoho varieties have genetically incomplete ovules. Characteristics: The ovule abnormality rate is as high as 48%, and its filaments are rolled back, which is not conducive to pollination. Some varieties have structural defects in the female flowers, some have degenerated stamens, and unreasonable arrangements of pollination trees in female-flowering varieties will cause flower and fruit drop.

2. Insufficient nutrients stored in the tree body

Insufficient nutrients stored in the tree body during the early growth period of grapes lead to an increase in incomplete flowering, poor embryo development, low pollen germination rate, and fruit drop. Due to the large number of grape flowers, the consumption of water and nutrients is also very large. When the grapes lack trace elements, especially potassium, phosphorus, boron and other elements during the flowering period, the fertilization ability of the flowers will decrease, resulting in flower and fruit drop.

3. Improper cultivation and management technical measures

Unreasonable fertilization plan, excessive use of nitrogen fertilizer before flowering, excessive watering during flowering, shaping and pruning, new shoot binding, topping, whole ears, etc. Improper implementation of technical measures will intensify the contradiction between vegetative growth and reproductive growth during the flowering period, resulting in flower and fruit drop. Spraying during the flowering period will burn the stigma, affect fertilization, and cause fruit drop.

4. Meteorological factors

(1) Temperature during flowering period: The optimal temperature during the flowering period of grapes is 20-25℃. If the temperature before flowering is lower than 10℃, it will affect the normal differentiation of flower buds; If the temperature during the flowering period is lower than 14°C, the flower organs will be stunted and fall off; if the temperature during the flowering period exceeds 35°C, the flower organs will easily become wilted and necrotic.

(2) Rainfall during the flowering period: Continuous rainy weather during the flowering period makes it difficult for the corolla to fall off, and the anthers cannot disperse powder normally.

(3) Insufficient sunshine: Continuous lack of sunshine before flowering reduces the assimilation of new shoots, and the nutrient supply of the fruit spikes during the flowering period is tight.

5. Physiological fruit drop

When the grape berries grow to 3-4 mm in size, some of the fruit berries will stop developing and fall off due to malnutrition.

Baidu Encyclopedia--Grape Cultivation Technology

Baidu Encyclopedia--Grapes