Reducing Botrytis in Table Grapes

Crop Nutrition and Botrytis in Table Grapes

Nitrogen

Vigorous growth, as a result of too much nitrogen, increases the susceptibility to diseases such as Botrytis.

Potassium

Getting the potassium:nitrogen ratio right can help minimize the effects of botrytis and also help reduce viral infections. When the balance is favor of nitrogen, plant growth increases and the concentration of plant growth increases and the concentration of plant exudates (e.g. sugar and amino acids) in the fruit rises.

This helps any spores that are present to germinate and spreads the disease on leaves and fruit. High levels of potassium prevent the formation of these exudates – thus a high K:N ratio minimizes disease effects. Optimum K:N ratios vary according to the variety.

Calcium

Calcium is beneficial in aiding plant resistance to diseases such as botrytis on the vine. It does so by strengthening the cell wall and thereby reducing disease ingress. 

It plays an essential role in lignification and wood maturity that it enables the table grape to tolerate frost and diseases. Foliar spray of calcium at post and pre Versaison growth stages resulted in reduction of incidence of botrytis.