A Detailed Guide to the Benefits and Key Techniques of Bagging in Grape Cultivation

There are many varieties of grapes, and because the climate and geographical conditions vary from place to place, the varieties grown also differ. In the process of grape cultivation, bagging techniques are often used to increase economic returns. So what are the benefits of using bags? What are the key technical points?

1. What are the benefits of using bags during grape cultivation?

1. It reduces pests, diseases and bird damage, and can also prevent sunburn, black pox, anthracnose, white rot and other diseases on the clusters, as well as avoiding damage from fruit-eating pests, grape moths and scarab beetles.

2. After bagging, the number of pesticide applications on the clusters is reduced, and since the fruit does not come into direct contact with pesticides, pesticide residues are lowered.

3. It can reduce the occurrence of fruit cracking, keep the fruit surface clean, preserve the bloom intact, make the grapes beautiful in appearance and increase their commercial value.

2. What are the key technical points of grape bagging?

1. Preparatory work before bagging

The management work before grape bagging mainly includes fertilizer and water management during the berry-swelling stage, cluster thinning, and pesticide application before bagging.

Fertilizer and water management: strengthen fertilizer supplementation during the berry-swelling stage, with heavy applications of phosphorus and potassium fertilizers; water-soluble fertilizers can be used to replenish the nutrients of the vine, or 30-50 kg per mu of 15-15-15 potassium sulfate compound fertilizer can be applied as a top dressing; for foliar fertilizer, mainly spray calcium fertilizer, and apply high-potassium foliar fertilizer after the hard-pit stage.

In the north, where water is scarce, take care to irrigate promptly after fertilizing; in the south, where there is abundant water, take care to drain accumulated water from the vineyard promptly.

Cluster thinning: if the cluster is too tight and the berries too densely packed, it is easy for pesticide sprays to fail to penetrate, ventilation and air movement are poor, and later on it easily causes cracking, gray mold, sour rot and so on. Therefore, cluster thinning work should be carried out.

Pesticide application before bagging: before bagging, spray the clusters with pesticide, which makes it easy to achieve thorough penetration, completely eliminate the pathogens on the clusters, and place the grapes in a sterile environment after bagging, reducing the probability of disease developing later.

2. Choosing the timing of bagging

Grapes should be bagged as early as possible, generally starting immediately after the fruit set is stable and cluster trimming and berry thinning are finished, and completed before the rainy season arrives, so as to prevent diseases from early infection and sunburn.

If bagging is done too late, the berries enter the coloring stage and sugar begins to accumulate, so not only are pathogens extremely likely to infect the fruit, but sunburn and insect damage will also occur to a relatively large extent. In addition, bagging should avoid the high temperatures after rain; after continuous overcast and rainy days followed by sudden clear skies, bagging immediately will aggravate sunburn, so wait 2-3 days to let the fruit adapt slightly to the high-temperature environment before bagging.

3. Bagging method

The correct bagging method is to use the right hand to open the bag mouth, so that the whole fruit bag puffs up, and use the left hand to support the bottom of the bag, so that the ventilation and drainage openings on both sides of the bag bottom open up and the bag body swells; then pull the bag upward from below, place the fruit stalk at the slit at the top of the bag, and position the cluster in the center of the bag. Then tie the bag mouth tightly with wire to prevent rainwater from flowing in. Be careful not to grab the cluster or the berries with your hands; let the cluster sit naturally in the center of the bag, and after bagging, gently place the fruit bag under the leaves and cover it with leaves to prevent sunscald.

It is also worth noting that if the bagged fruit has no leaves for shade, an additional paper cap should be placed over the clusters on the west or south side of the grapevine to reduce sunscald. After bagging, if high-temperature weather occurs (above 38°C), the bottom opening of the bag should be opened for ventilation to lower the temperature inside the bag. Bagging work is best completed within 7-10 days.