Causes of and Control Methods for Uneven Berry Size in Grapes

Grapes have a sweet-and-sour taste and are a fruit many people love. However, uneven berry size often occurs when growing grapes, and uneven berry size in grapes is a common situation in every grape-growing region of our country. After fruit set, grapes often show inconsistent growth, with some berries large and some small. There are many causes for this situation, and treatment must be tailored to the condition of the grapes and the orchard.

1. Variety-related causes

The cause of uneven berry size in grapes may be that, when selecting a variety, a variety that is inherently prone to producing uneven berry sizes was chosen. For example, Victoria: due to its own genetic makeup, Victoria is inherently prone to poor pollination and fertilization, and poor pollination naturally leads to uneven berry size in grapes, with the small berries generally having no seeds or very few seeds. In this case, one can avoid choosing such a variety when selecting varieties, or carry out a seedless treatment on this variety so that all berries have no seeds, and then carry out enlargement treatment, and the berries will no longer show this situation.

2. Boron and zinc deficiency

If grapes lack boron during growth, it becomes difficult for pollen to pollinate, the ovules cannot be fertilized, seeds cannot form in some berries, and fruit set decreases accordingly. If zinc is deficient, it leads to insufficient auxin in the grape plant, reduced fruit set, and difficulty for the flower caps to fall off, producing uneven berry size. If boron and zinc deficiency occurs in the orchard, supplementation should be carried out immediately according to the specific situation, with additional boron and zinc fertilizer.

3. Adverse weather

If continuous high temperatures or rainy weather occur during the grape flowering period, they will lead to difficulty in pollination, poor fertilization, and difficulty in fruit set, forming uneven berry size. If clusters shaped like an “H” are found in the orchard, that is mostly uneven berry size caused by weather reasons. Many friends in the north worry that grape yield will be poor, so they do not water the grapes before flowering, but if high temperatures occur, this will cause the grapes to drop flowers and berries. When low temperature and rainy conditions occur, a film should be placed over the grapes, lighting equipment should be installed inside the film, sufficient temperature and light should be given to the grapes, and drainage should be timely. If continuous high temperature and drought occur, sufficient water should be supplied to the grapes during the flowering period. Ensure the water requirement.

4. Hormone problems

There are several stages in grape growth when hormones need to be used; if hormones are used improperly at these stages, it will lead to poor development of the grapes. For example, in the first period, when elongating the flower clusters, gibberellic acid needs to be applied, but if it is not applied in time, it will affect pollination and cause the berries to be generally small. The second is at the flowering stage; during the flowering stage many friends use fruit-setting agents to promote fruit set, but improper use will lead to poor pollination and the berries cannot expand normally. The third is at flower drop, when growers use expansion agents too early, the seeds abort, and the berries cannot expand. All kinds of hormones must be used reasonably at each stage; if one does not know how to use hormones correctly, one should use less or not use hormones.

These four are the most common causes of uneven berry size in grapes. Of course, there are many other causes, such as growth vigor, density, and so on, which the editor has not listed all of here. Among them, the most noteworthy are the use of boron and zinc fertilizer and hormones; whether deficient or excessive, they will seriously affect the normal growth and development of grapes, so their use must be given attention!