Preventing Bunch Stem Necrosis in Table Grapes

Bunch stem necrosis is a disorder known under many different names. It can occur around flowering or at veraison, sometimes even later in the season. Crop nutrition is an important factor influencing bunch Stem Necrosis in table grape.

Crop Nutrition and Bunch Stem Necrosis in Table Grapes

Nitrogen 

Too much nitrogen causes excessive vigor which again causes primary bud-axis necrosis, restricting table grape yields. Over-use of nitrogen has been implicated in the physiological disorder, bunch stem necrosis.

Magnesium

Magnesium deficiency is also associated with bunch stem necrosis. The disorder affects table grape fruit set and fruit ripening. 2-3 foliar applications of magnesium starting just before veraison minimizes the problem. Bunch stem necrosis is also linked to an imbalance of magnesium with potassium and nitrogen. 

Research suggests that low levels of sugars in storage organs and table grape fruit lead to nitrogen accumulation, particularly during cold weather at maturation. In this situation, magnesium sprays can help reduce bunch stem necrosis.

In a similar fashion , a foliar spray with magnesium helps correct the imbalance of too much Potassium-uptake again preventing bunch stem necrosis. However, while foliar sprays can help, long-term magnesium shortages should be corrected using soil applied or fertigated magnesium fertilizer in a standard maintenance programme.