Drying of berries is one of the problems that winegrowers face in the process of growing this fruit crop. Moreover, it occurs at all stages of maturation. In addition to fungal infections, drying out can have three other main causes. Namely, the berries have received sunburn, the grapes are infected with bacteriosis, or the plant is damaged by the buffalo leafhopper. Let's talk about the main signs, control and prevention measures.
Sunburn of grapes
Although grapes are a heat-loving plant, they can suffer from excessive solar activity. In hot weather, when the thermometer shows 30°C and above, sunburn may appear on the berries. They look like small spots of gray or brown color.
Such damage also occurs with some grape diseases. Therefore, you need to pay attention to the place where they formed. If the spots are on top of the illuminated side of the bunch, then it is a burn. Location in other places may be a sign of bacteriosis.
How to help grapes with sunburn of berries
It will no longer be possible to save sun-burnt berries. They must be carefully removed by hand without damaging other fruits. To prevent healthy berries from being damaged by sunlight, either individual clusters or the bush as a whole should be protected from the sun.
So, the bunch can be wrapped in a thin sheet of white paper, connecting the edges together. The bush is saved from the sun by covering it with tulle or other light fabric. But this method impairs the ventilation of the grapes, which can lead to the development of a fungal infection. Therefore, it is worth taking care of the prevention of sunburn of berries in advance.
To do this, during the process of forming a bush, its branches are placed on horizontal structures in the form of a gazebo. In this case, the bunches are protected from the sun by a canopy of grape foliage.
Bacteriosis of grape berries
By external signs, bacteriosis of grape berries resembles their sunburn. Spots appear on fruits due to special bacteria Bacillus viticola, which are carried by sucking insects.
It is rare to notice a problem at an early stage. Bacteriosis appears after flowering, when the berries are still small, up to 1 cm in diameter. Light spots form under the skin and are almost indistinguishable. The skin itself looks quite healthy. Gradually, the spot turns into a brownish-violet depression, and the pulp of the berry begins to dry out. After 5-7 days, the entire fruit dries up.
Since bacteriosis selectively infects berries, other fruits may not be affected by the disease. And at the stage of ripening of berries, new infections no longer occur.
How to prevent bacteriosis of grape berries
Chemical substances that can resist bacteriosis pathogens have not yet been developed. Therefore, it is impossible to cure it. Berries infected with bacteria will still dry out. In order not to spoil the appearance of the bunch, they can be removed.
To prevent bacteriosis, immediately after flowering, bushes are treated with insecticides to prevent the appearance of insects that carry the disease.
Planting grape varieties that are resistant to it will also help to avoid bacteriosis.
Buffalo leafhopper on grapes
Grape berries also dry out due to the buffalo leafhopper, which causes irreparable harm to the bush. If earlier it was noticed on fruit trees: apple trees, pears, plums, peaches, apricots, then recently it has begun to cause trouble for winegrowers.
The pest, feeding on the sap of the plant, makes characteristic ring-shaped lesions on the shoots. Because of them, the berries do not receive enough nutrition and dry out, and the shoots wither and die. In addition, the female leafhopper lays her eggs on young shoots so that nodules (swells under the bark) form on them. Vines with such damage must be removed.
How to deal with buffalo leafhopper
The insect gives birth once per season. In the larval stage, the pest lives and feeds on herbaceous plants under grape bushes. An adult insect moves onto the vine and begins to harm it.
If you do not fight the buffalo leafhopper, then in a few years the grapes will die!
You can catch an adult insect, but this is not easy, because it is very agile and sees well. It is easier to catch it at 4-5 am, when the pest is least active. This is usually done after the berries have ripened.
To make the leafhopper larvae less likely to survive, it is advisable to keep the soil under the bushes clean and dig up the area in the fall. You can also plant onions or garlic next to the vine, which repel insects.
In June, with an interval of 10 days, double spraying with insecticide is carried out. It is necessary to process both the grapes and the grass under them and nearby trees and shrubs. Regular weeding is also a good prevention of pest occurrence.
Grapes dry out for other reasons. The plant may be infected with fungal infections such as mildew, anthracnose or verticillium. There is also crest paralysis, the causes of which are unknown. Fruits can also dry out due to mechanical damage, drought, and improper gartering of bunches for support.
