While everyone is in a tizzy about the appearance in the Napa Valley of the European grapevine moth, and understandably so, there are many other threats to the vintage that the winegrower must face every growing season. Just this past Monday (May 10th) we had an exceptionally late spring frost. Rain is forecast for this coming Monday and, with bloom nearly upon us, heavy rainfall now would be disastrous for fruit set.
Possibly the biggest headache for winegrowers every year is powdery mildew (Uncinula necator), a fungal pathogen that infects all green, succulent tissue on the grapevine, including leaves and young berries. Powdery mildew (PM) can cause extensive crop loss and poor wine quality if left untreated. Temperature is the most important factor influencing the development of PM: it positively thrives in temperatures between 68-81 degrees F. Vitus vinifera cultivars vary in susceptibility to PM, but the principal control method for preventing infection in all cultivars is the application of sulphur in wettable and dust forms.
It is looking like 2010 is going to be a bumper year for this particular disease as we have had no hot weather this spring. So far this year, each sulphur application in Vinoland has been followed by a rain event making it difficult to get the upper hand in preventing further germination of conidia. But, perseverance is the key and so Vinomaker was out spraying the vines today and could oft be heard muttering to himself the mantra, win early.