Cranberry 
Cranberries are affected by a number of fungi that destroy the 
fruit both in the field and after harvest. Apparently some of 
these fungi infect the fruit early in its development. Fruit rots 
that do not appear until August can be controlled by spraying the 
vines in the blossom period. Spray treatments are only about 50 
percent effective, however, and fruit rots are an important problem 
in all the cranberry-growing areas. Another important problem in 
Massachusetts, Wisconsin, and New Jersey is false blossom, a virus 
disease, which eventually makes the plants nonproductive. Control 
is difficult. Insecticide sprays to eliminate the insect vector 
and the planting of klendusic varieties (varieties that do not be-= 
come infected because for some reason they are not attractive to 
the insect) are standard procedures at the present time. 
Grapes 
Climatic factors are so important in commercial grape production 
that the high-quality European table grapes can only be grown in 
the Western States. 
In the East the American bunch grapes are affected primarily with 
black rot and downy mildew. The black rot fungus infects all the 
green parts of the plant and causes a severe rotting of the fruit. 
Black rot is much more difficult to control in the southern part 
of the country. Downy mildew, on the other hand, is mainly a leaf 
disease that affects the metabolism of the vines. These diseases 
are a constant threat to the industry and require the use of copper 
compounds and dithiocarbamates in sprays. 
In the West the vinifera or European grapes are attacked mainly 
by the powdery mildew fungus, which spots the leaves and fruit. 
Affected fruit is apt to crack and mold in transit. Powdery mildew 
is readily controlled by sulfur sprays. The vinifera varieties 
are very susceptible to the black rot fungus, but fortunately 
western climates are too dry for the disease to develop. Pierce's 
disease is important and widespread in California where it has 
greatly reduced production in many vineyards. In some parts of 
the State it has caused or hastened the replacement of grapes by 
some other crop, The causal virus attacks numerous other plants, 
including alfalfa (alfalfa dwarf) and many grasses. It is carried. 
by an insect vector from one host to another. Diseased alfalfa 
fields are a source of infection for nearby vineyards, and vice versa. 
Hazelnuts (Filberts) 
Hazelnuts are grown commercially in Oregon and Washington. Bacterial 
blight is present in all the plantings. The organism attacks the 
buds, leaves, branches, and trunk of the trees. The nuts are rarely 
attacked directly, but the size of the crop is reduced by the killing 
of the fruiting twigs. Copper sprays applied in the fall and early 
spring are effective control procedures. 
