The relative extent of the use of copper and dithiocarbamate fungicides varies with the section in which tomatoes are grown. In southern Florida, zineb and nabam have proved to be superior to the copper fungicides for late blight control and have been generally used. There has seemed to be some preference for the dithiocarbamate materials throughout the South Atlantic States, although copper fungicides also are recommended for use in tomato disease control.

In the North Central, North Atlantic, and Northeastern States, copper fungicides are commonly used for control of late blight although the dithiocarbamate materials also have been extensively used.

Seedbeds need protection from leaf spot diseases. Often they are sprayed or dusted three or four times before the plants are taken to the field. In the field, the first applications of fungicides usually can be made about 30 days after the first flower cluster blooms. Later applications can be made at 10-day intervals unless there are frequent rains, when the interval may have to be reduced to 7 days, or even less, to secure good control.

Spraying has proved to be superior to dusting in the control of tomato diseases but, when wet soil makes it impossible to use heavy spraying equipment, dusting is a very valuable adjunct.

The coverage obtained with ground dusting machines has been superior to that secured from applications of dust by airplane.

We have no commercial varieties of tomatoes resistant to mosaic diseases and must depend on measures of sanitation to prevent infection. After the diseases appear in the field or greenhouse, it is hard to check their further spread. Therefore the best means of control consists of preventing infection in the seedling plants and thus delaying the appearance of the disease until a crop is well started. If that can be done, the loss is likely to be less severe.

One should never handle seedlings without first washing his hands with soap and water to remove any virus from the hands. Because manufactured tobacco may carry the virus of tobacco mosaic, no one should smoke or chew tobacco while handling the plants. Workers can stop at intervals for a smoke and then wash their hands before again touching the plants.

All perennial weeds around the seedbeds and in or near the fields should be destroyed because they may carry viruses of tobacco or cucumber mosaic.

Every effort should be made to prevent aphid infestation of the seedbed by using insecticides regularly.

When seedlings are grown in a greenhouse used for commercial tomato production, the seedlings should not be handled after working with older plants unless the hands have first been washed. Anyone who has worked in a potato field or peeled or cut potatoes should wash the hands before working with tomatoes.

The removal of mosaic plants in the field usually is of little value in checking the spread of mosaic diseases and often leads to further infection through brushing the infected plants against healthy ones in the course of removal.

Because many nonparasitic diseases are induced wholly or partly by extremes of temperature or moisture, the grower is somewhat at the mercy of the elements where those disorders are concerned. In some diseases, however, both nutrition and weather have a part, and some losses may be avoided by care in the use of fertilizers, particularly nitrogen.

S. P. DOOLITTLE is a pathologist in charge of investigations of diseases of tomatoes, peppers, cucurbits, and other vegetable crops in the division of vegetable crops and diseases of the Bureau of Plant Industry, Soils, and Agricultural Engineering. He is author of Farmers' Bulletin 1934, Tomato Diseases.

Gray ear rot on corn.