Influence of Berry Shrivel on Mineral Nutrition on Cabernet Sauvignon

Berry shrivel is a disorder that becomes apparent between veraison and harvest. Berries on affected clusters become flaccid while the rachis appears to be healthy. This is unlike waterberry which is known in other grape growing regions as bunch stem necrosis, stalk necrosis, shanking and other terms related to necrosis of the rachis. Symptoms of berry shrivel do not include necrosis of the rachis. In affected bunches, all portions of the rachis, including the pedicles, usually appear normal throughout the season. Similar to waterberry, berries in clusters with berry shrivel do not ripen normally. They are not fully colored and the juice tastes sour and may have off flavors. The fruit is unacceptable to wineries and is often selectively removed prior to harvest. The cause of berry shrivel is unknown at this time.

In 2003, berry shrivel developed in two of the three vineyards monitored for this project. At one site, soluble solids were reduced at veraison, onset and harvest in both symptomatic and non-symptomatic clusters from affected vines when compared to clusters from non-symptomatic vines. Thus, even at veraison, prior to the onset of visual symptoms, each type of cluster from affected vines had reduced Brix when compared to clusters from unaffected vines. In addition, at harvest titratable acidity, malic and tartaric acids were greater in juice from symptomatic and non-symptomatic clusters on affected vines when compared to clusters on non-symptomatic vines.

At the second site, soluble solids were reduced in symptomatic clusters from affected vines only at symptom onset and later. Thus, Brix found on non-symptomatic clusters taken from affected vines was not significantly different than brix found on clusters from unaffected vines. At harvest, only juice from symptomatic clusters on affected vines had greater titratable acidity, malic and tartaric acids.

At each site, the ratio K/(Ca+Mg) tended to be lower in the rachis tissue of vines with berry shrivel at onset of symptoms and at harvest. This was due to potassium tending to be lower in affected vines at one site and calcium and magnesium tending to be higher in affected vines at a second site.

There was no consistent trend for differences in total percent nitrogen or ammonium-nitrogen in the rachis tissue of symptomatic and non-symptomatic clusters by sample date or site. Petioles collected at bloom, veraison, onset and harvest at both sites did not indicate any differences in total N, nitrate-N or ammonium-N between symptomatic and non-symptomatic vines in 2003.

At one site, leaf water potentials were measured at veraison and shortly after onset of symptoms. Vines that ultimately showed berry shrivel had higher leaf water potentials (less stressed) than non-symptomatic vines both at veraison and onset of symptoms. Leaf water potential measurements taken at the second site were not as clearly defined by vine symptom.