What's wrong with grapes falling off when touched

The dropping of grapes upon contact may be related to factors such as high maturity, mechanical damage, disease infection, improper water management, and variety characteristics.

1. Excessive Maturity

In the late stage of grape fruit ripening, the detached cells at the junction between the stem and the grain gradually decompose, leading to a decrease in grain adhesion. Overripe grape pectinase activity is enhanced, accelerating the separation of fruit flesh and stem, and easily shedding upon slight touch. Before harvesting, it is necessary to observe changes in the color of the fruit skin and the sugar acid ratio to avoid delaying harvesting after the ripening period.

2. Mechanical damage

compression and collision during transportation or cultivation can lead to breakage of the fruit stalk vascular bundle. Especially for varieties with tightly packed fruit grains, friction between them can damage the skin of the fruit stem, forming invisible wounds. During field operations, human touch should be minimized, and scissors should be used for harvesting. When packing, cushioning materials should be used to separate the fruit clusters.

3. Disease invasion

Fungal diseases such as gray mold and powdery mildew can damage the fruit stem tissue. The enzyme substances secreted by the gray mold fungus dissolve the cell wall, causing the fruit stem to rot and become brittle. In the early stage of the disease, brown water stains can be seen on the fruit stalk, and in the later stage, a gray mold layer is produced. It can be sprayed with azoxystrobin or putrescide for prevention and control, and attention should be paid to controlling the humidity in the field.

4. Improper water management

The sudden encounter of rainstorm or excessive irrigation before harvest will make the pulp cells rapidly absorb water and expand, and the pressure on the fruit stalk will increase. Sudden dampness after drought can also cause longitudinal cracks in the fruit stem. Soil moisture content should be kept stable, water should be controlled appropriately during the maturity period, and harvesting should be delayed after rain.

5. Variety characteristics

European and American hybrid seeds such as Jufeng have thinner and crisper fruit stalks and obvious delamination development. And European and Asian varieties such as red grapes have a high degree of lignification on their fruit stems, making them less prone to shedding. When cultivating, one can choose varieties with thick fruit stems or enhance the toughness of fruit stems by spraying calcium fertilizer.

Regarding the issue of grape drop, it is recommended to strengthen pre harvest management. Keep the orchard ventilated and transparent, and regularly remove overly dense fruit clusters. Stop irrigation two weeks before harvesting and avoid operations on rainy days. During transportation, use breathable packaging boxes and place them in a single layer to avoid stacking. The storage temperature should be controlled at around zero degrees Celsius, and the relative humidity should be kept at a high level. Gently rinse with running water before consumption, avoiding rubbing the fruit ears with force. If diseased fruits are found, they should be promptly removed to prevent the spread of mold and infection of healthy fruits.