Coulure

In the irrigator in viticulture many flowers ( trickling ) or small berries are repelled from the stem scaffold unusual. Normally, the proportion of flowers that develop into berries depending on grape variety with only 30 to 60 percent ( = Durchblührate ) is. This is normal because the vine could not possibly bring all the fruit to full maturity. The irrigator is a fertilization disorder and thus belongs to the family of the physiological disturbances of the vine. The fertilization failure can occur up to 3 weeks after flowering. Often, the climatic conditions play an important role during this time. As a result, the irrigator, it comes to millerandage and thus to a reduction in yield. Some varieties such as Grenache, Malbec, Merlot but also Ortega and Muscat Ottonel have an increased tendency to coulure.

Cause and effect

For the flowering of the vine (stage 61 according to the BBCH-scale for vine ) is the average daily temperature at least 15 ° C must be better but 20 - 25 ° C. When flowering pollination of the flowers is done. At a berry set occurs when at least one ovule is fertilized in an ovary. Without pollination by the pollen tube is small seedless Virgin berries can form. In particular, the varieties Huxelrebe and Gewürztraminer tend to form Virgin berries.

The trickling, so the repulsion of flowers or small berries can have many causes. All causes in common is a disorder of carbohydrate supply in the plant tissue:

• Climatic conditions: rain, cold, but also great heat during flowering, the development of the ovum, the pollination or fertilization interfere.
• Lack of light, strong defoliation of the vines, chlorosis or hail during the flowering affect the supply of flower with assimilates.
• Nutrient deficiency or excess may lead to an impairment of fertilization. The boron plays an important role in fertilization. But a lack of the elements molybdenum, zinc or phosphorus lowers the Durchblührate.
• Unadjusted vigor (excessive or weak growth ) due to poor pruning, an unadjusted vine training or the wrong rootstock can lead to the irrigator.
• The treatment of the vines with copper ( → Bordeaux mixture ), high-dose wettable sulfur or foliar spray trigger the shedding of flowers or berries.
• The inappropriate use of herbicides, too high a proportion of harmful gases such as sulfur dioxide as well as various pests such as red torch or Eutypiose may be responsible. Excessive irrigator can also be a symptom of fanleaf disease.

Measures

The influence of the winemaker is limited. It falls usually difficult to refrain from grapes such as Gewurztraminer, Merlot and Malbec. In the context of modern clonal selection, however, succeed in filtering out less susceptible varieties of grape varieties mentioned. The thinning of supernumerary shoots can reduce nutrient deficiency per bunch. A reliable means represents the shoot tip cap to direct the force of the vine on the inflorescences already formed.

The selection of suitable rootstocks for the vigor of the vine can be adapted to local conditions.