Sour rot disease in vines is a serious disease that sometimes causes the loss of the entire crop. The disease begins with the formation of a microscopic crack in the grape skin, through which various pathogens that break down acetic acid (the source of the bad odor in a sick vineyard) penetrate. So far, no pests have been found that can cause the crack in the shell to form. It has been speculated that perhaps the level of turgor (water) pressure inside the grape is the cause of the cracks.
Since vineyards are subject to a high spray regime, maybe one of the spray materials is responsible for creating the cracks.
In a complex experiment (a doctorate by a Volcani researcher), the environmental, physiological and/or genetic factors for this phenomenon were examined. The study is expanding in many directions, but so far there has been very slow progress in the results. It appears that a combination of climatic factors – warming, high humidity and irrigation regimes are the main factors for disease spread. An experiment that involved changing the irrigation regime resulted in a 25% annual damage reduction. This is certainly encouraging, but not totally satisfying.
The economic loss to farmers led to the marketing cessation of very successful varieties, such as Sultanina and Thompson, which suffered greatly from sour rot.
During my visit data was collected and hopefully by December I will be able to report on more optimistic findings.