Why do grapes dry?
Disease and pest infestation in the vineyard often causes serious damage to the vine. If the leaves dry on the grapes, the shoots wither and die off, this becomes a heavy loss for the grower. It is twice as big a misfortune when the brushes suffer, the berries dry up and a significant part of the harvest is lost. Moreover, the drying process can begin both immediately after setting the berries, and already during their ripening, be accompanied by symptoms inherent in cultural diseases, and proceed for no apparent reason.
Why do berries dry on grapes? There are many reasons for the loss of bunches. Most often, growers identify diseases caused by pathogenic fungi.
Downy mildew is in the first place in terms of harmfulness, affecting not only the ridges and clusters of grapes, but also the green mass, new and perennial shoots. The fungus, penetrating into the tissues of the plant, prevents the flow of food and moisture. Infected parts of the vines, including brushes and ripening berries, dry out and die.
Mildew is not the only crop loss problem. There are other diseases of grape berries, photos with the effect of which on the vine clearly prove the degree of danger and the need to combat them. Insect pests can cause serious damage to the crop, there is a risk of loss of berries and in case of insufficient vineyard care.
The vine disease caused by the fungus Eutypa lata is widespread in all wine-growing regions where winters cannot be called mild, and is especially damaging in seasons with high rainfall..
Since the pathogenic fungus is able to penetrate the tissues of not only grapes, but also many other horticultural and fruit crops, this complicates the fight against the manifestations of the disease and its spread. The disease affects not only shoots and berries, changes in the wood caused by the fungus are clearly visible in the photo of the grape disease. The disease especially strongly affects adult grape bushes, aged from 8 years, and the symptoms of dry-handedness become obvious when the plant at the beginning of summer gives an increase in length of 20-25 cm.
Shoots and leaves are stunted, oh, the size and color are different from healthy ones. The leaves dry on the grapes, and then necrosis affects the affected shoots. Berries that have tied dry or stop growing, and remain small until the end of the growing season.
Spotted anthracnose grape
One of the reasons why grapes dry out may be anthracnose. The peak of infection with this serious disease occurs during wet periods, and the pest is active not only in warm weather, but in the range of 2-30 ° С.
Manifestations of anthracnose are often mistaken for mechanical damage to berries and shoots caused by hail. But the weather has nothing to do with it.
Rounded necrotic spots with a brown-black border are the zones of penetration of harmful fungi. Such spots can merge, the dried-up affected tissues inside them are destroyed, and the young leaves drying on the grapes seem to be burnt..
The disease infects all aboveground green plant organs, including the brushes. The grape disease, in the photo, presents the greatest danger to berries before flowering, when the whole brush is affected, as well as before the harvest ripens. As the disease progresses, spots characteristic of the disease form on the ovaries and ridges, after the growth of which the brush withers in whole or in part..
Verticillary wilting of the vine
Verticillosis, namely the causative agent of this disease, the pathogenic fungus Verticillium dahliae, penetrates the roots through the soil and, multiplying, disrupts the supply of moisture to the shoots and clusters of grapes. Grape berry disease, as in the photo, more often and more strongly affects young plants, and its external manifestations can become visually noticeable only a year or two after infection.
The vineyard suffers the most severe damage when the bushes are under high stress. This is more often observed with a lack of moisture, elevated air temperature and the beginning of ripening of berries. First, leaves that look like burnt dry on the grapes, then it is the turn of shoots and bunches. The brushes located in the lower tiers of the affected shoots dry, individual berries on the grapes dry, mummify and remain in this form on the bunches.
Buffalo leafhopper, which increasingly attacks vineyards, can inflict no less harm than pathogenic fungi..
An insect that feeds on plant juices, on the shoots and ridges makes characteristic ring-shaped lesions, up to a centimeter long, as a result of which the grapes, which are not receiving enough nutrition, dry up, the shoots wither and die off.
The pest gives one generation per season. In the stage, leafhoppers larvae live and feed on grassy plants under vine bushes, and then adult insects climb the vine and begin their harmful activity.
The spread of the pest is facilitated by the abundance of vegetation near the vine bushes. A measure of the fight against a dangerous insect is a two-fold treatment of plants with benzophosphate. Such spraying should be carried out in June, and, in addition, removing weeds and planting beds with onions and garlic near the vineyard, which frightens off leafhoppers, will be a good prevention..
Bending of the ridges during berry ripening
An explanation of why berries dry on grapes can be the ripening bunches themselves, under whose weight the bunches bend, the supply of moisture and nutrients is disrupted and the fruits wither.
The risk of loss of yield for this reason is greatest for varieties and hybrids that form heavy large clusters..
You can avoid breaking the ridges and shoots bearing brushes if you grow a bush based on an arch or a gazebo. The hands hanging down are not constrained and develop well, and the branches are evenly loaded and do not bend.
Drying grape ridges
If no apparent reasons, for example, symptoms of diseases of grape berries, as in the photo, are identified, and the brushes are not poured, and the berries are mummified, perhaps we should talk about drying out of the ridges.
This phenomenon, first noticed a little more than a century ago, has not yet been sufficiently studied, it has only been found out that a kind of paralysis, leading to a slowdown or arrest of the development of bunches, is associated with metabolic disorders and is of a local nature. The disease is not infectious in nature, is not transmitted to other plants and may be associated with a violation of the ingress of moisture through the vessels of the ridge to the ripening berries. Indeed, it is during dry periods that paralysis, leading to the drying out of grape berries, manifests itself most often.
Symptoms preceding desiccation, in the form of brown dark spots at the branches of the ridge, become noticeable during the ripening period, when the berries accumulate from 7 to 12% sugar.
The tissues under the spots are affected to the depth of several layers of cells, and the lack of moisture aggravates the picture and necrosis covers all new areas. If the spot on the ridge loops back, the flow of moisture to the brush located below stops, and the isolated grapes dry out, wrinkle and lose their taste and marketability..
Drying of the grape ridges is dangerous not only with the loss of harvest, but also by the fact that mold and disease-causing fungi often settle in the affected areas, causing secondary infection of the culture.
No direct relationship was found between the frequency of drying of the ridges, the region of growth and the grape variety. But empirically, it was possible to determine that self-rooted bushes are less likely to be affected by this disease of grape berries, as in the photo, than grafted plants, especially on vigorous rootstocks..
Treatment of paralyzed bushes with fungicides or other plant protection products is ineffective. In some cases, when the grapes dry out, spraying the plantings with a 0.75 percent solution of magnesium chloride or 3 percent magnesium sulfate helps. Prophylaxis begins about a month before the probable onset of paralysis, and then two more sprays are carried out with an interval of 10 days.
As an effective prevention, when the berries begin to take on color and gain juice, the bunches and the surrounding area are treated with a 5% solution of magnesium sulfate.
However, the main means of combating the drying out of grape ridges, gardeners consider compliance with the rules of agricultural technology. Only with proper formation and pruning of the vine, the use of balanced fertilizing, including magnesium and a moderate amount of nitrogen, as well as with sufficient watering of the vineyard in combination with chemical treatment, can we talk about the elimination of paralysis of the ridges and saving the crop.