4s probably the most serious disease affecting the crop. It is 
especially damaging on susceptible varieties, but fortunately 
only about one-tenth of the acreage is planted to these varieties. 
Leaf spots due to various fungi, crow gall, and nutritional 
troubles all help to reduce the size of the crop. These diseases 
occur every year and require numerous applications of bordeaux 
mixture or zinc dithiocarbamate. 
Strawberries 
Strawberry plants are affected by various leaf spot fungi, and 
some fungi have been isolated from the mature fruit. These leaf 
and fruit organisms are responsible for appreciable losses in 
certain seasons. However, plant pathologists consider the losses 
from these fungus diseases to be minor in comparison with those 
from virus diseases, such as yellows, crinkle, leaf roll, and 
witches'-broom. These diseases are widespread, and some plantings 
show from 80 to 100 percent of the plants affected. The plants 
are stunted and made unproductive, and the size and quality of 
the fruit are materially reduced. The only control is to develop 
stocks of virus-free plants and prevent their subsequent infection 
by the control of insect vectors. 
Tung Trees 
Tung trees are cultivated on a commercial basis in a narrow belt 
approximately 100 miles wide along the Gulf of Mexico from eastern 
Texas to Florida. In general, this crop has been free of fungus 
diseases, but occasional plantings are affected by the thread- 
blight fungus. The fungus kills leaves and twigs, and the yield 
of nuts is accordingly reduced. Fortunately the disease is readily 
controlled with one application of bordeaux mixture. Occasionally 
the trees are attacked by a bacterial organism causing a definite 
leaf spot, but the loss generally is minor. The main problems in 
the growing of tung trees are nutritional conditions, most of which 
can be corrected by proper fertilizer applications. 
Walnuts 
Blight due to a bacterial organism is destructive in the extensive 
commercial plantings of walnuts in California and Oregon. The 
disease primarily affects the nuts, but it may also spot the leaves 
and blight the blossom clusters early in the spring. Bordeaux 
mixture or copper-lime dusts will control the disease, and generally 
at least four applications are necessary each season. 
Vegetable Crops 
The estimates of disease losses in vegetable crops, as given in 
Table h, include only the important commercial crops on which 
reasonably accurate data are available. Serious losses are known 
SSO 
