Grapes grown in the Northeastern USA tend to have lower sugar levels and higher acid levels as compared with those grown in California which has the reverse - higher sugar and lower acid. This is important in wine making and wine blending. In the Northeast to make wine, the sugar needs to be raised and the acid reduced. Whereas in California, the sugar needs to be reduced and the acid raised.
Due to the rains, grapes grown in the Northeast tend to be susceptible to various fungal diseases (Anthracnose, Botrytis Bunch Rot, Black Rot, Downy Mildew, Powdery Mildew). Some grape cultivars, especially European vinifera, cannot be grown without heavy spraying or they are destroyed by these fungi. American and hybrid varieties are, however, more resistant.
Also insect and birds take their toll. Phylloxera affects certain cultivars and not others - it degrades the leaves and roots. The Japanese beetles eat away the leaves. Milky spore is a soil-borne bacterium that kills the white grubs of Japanese beetles. Spread on the ground per direction on the packaging gives effective Organic control. Netting of the grape vines will prevent birds from eating your whole crop.
Unfortunately, published disease charts are only a rough guide and do not tell the whole story. For example, 'Neptune' seedless grape, according to the charts, is moderately disease resistant. However, from my experience, 'Neptune' takes years to finally produce and when it does every grape rots away. Other grapes that are less 'disease-resistant', however, have done well in my garden.
In addition, a specific grape cultivar can do well in one area but not in another - even 100' away on the same property - particularly if a different elevation or wind flow. This is referred to as 'microclimates'.
The overall special combination of geography, geology, and climate on the grapes grown on a particular location is call 'terroir' by the French (pronounced tier-wha'). Changing the terroir, changes the taste and health of the grapes and grapevine.
Pruning is essential to grape production. Each year about 90% of growth is pruned out during the winter season to prepare for the next year.