Grapes have a variety of 'pests' that vary from mildly annoying to lethal for both crop and vine. Animals such as birds, deer, racoons, turkey - to name a few - love to eat both grapevine leaves and berries. Many insect species can also cause severe damage.
But by far the most difficult and time consuming pests to control (especially in the humid conditions found in the mid-Atlantic area) are fungal diseases. Listed below are links to the five major ones (each link has pictures and ways to control each disease).
The fungus attacks all green parts of the vine - the leaves, shoots, leaf and fruit stems, tendrils, and fruit. Its effect on the fruit is the most damaging.
Also known as 'Noble rot' (for its shriveling and dehydrating of the berries which can concentrate sweetness and flavors), uncontrolled botrytis can be disastrous.
A particularly 'sneaky' disease because infected berries only show symptoms close to the harvest. At that time it will be too late to contain the rot.
Foliar infections of this disease limit photosynthesis which causes all sorts of problems. The quality of infected fruit clusters will either be degraded (increasing suseptibility to bunch rot infections), or completely destroy them.
While extreme cases of downy mildew can destroy fruit, primarily it causes premature defoliation in the summer that can result in abnormal fruit development.
On fruit clusters it forms bird's eye shaped spots and can also cause leaf defoliation.