In addition to fungal diseases such as rot and mildew, viral diseases like leafroll and fan-leaf and bacterial infections such as Pierce’s Disease (PD) can cause problems in the vineyard. Viral diseases can decrease yield but will not kill vines, but PD is almost always fatal.
In addition to disease there are a host of pests, some that can be treated and some that cannot. Among the most difficult to treat are phylloxera and nematodes. These are small aphids that infect the roots of the vines, cause damage, and eventually kill the vine. These pests originated in North America, where the indigenous species of vine developed tolerance to them. The fine wine grapes of Europe had not and were thus killed when the pest was introduced into European vineyards during 19th century horticultural experimentation.
Besides phylloxera and nematodes, grape moths and spider mites are common pests that can severely damage vines, but they are much more easily treated. Other pests, such as birds, rabbits and deer consume the fruit and can be difficult to deter.
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Guyot training is a head trained, cane pruned system, where one to four canes are tied to a support wire. The buds along these canes send out the shoots, which are then trained on wires. Vines trained in this way provide grapes with more sunlight. This system is most often used in cooler regions where shading the grapes can prevent ripening, and the vines are exposed to the dangers of mildew and rot.
In addition to these mostly standard practices several other treatments can be used. Irrigation is frequently used in many New World winegrowing regions, although it is illegal in much of the Old World. In areas where rain falls throughout the year, such as Europe, irrigation is not normally necessary and could be easily abused to achieve higher yields. In many parts of California, Australia and South America, grape growing would not be possible without irrigation because the rainfall is insufficient and mostly falls only in the winter.