One could go on and on, multiplying illustrations, big and little, temporary or permanent, past or present, mere threat or realized actuality. For instance: Pierce's disease of grapes in California; the deficiency diseases, which are particularly important in Western States; cranberry false blossom in New Jersey; fire blight of pear, because of which "one of the greatest industries of the San Joaquin valley vanished like a dream"; verticillium wilt of cotton in the El Paso region of Texas; melon mosaic in the Imperial Valley of California; and many, many others throughout the world.

The essential feature of plant diseases however, is that they deprive everybody, not just farmers, of the plant products they destroy. The loss from all diseases of all crops is estimated to be about 10 percent. That is an average. Some crops suffer more loss.

Others are negligibly affected. The importance of any one disease depends on the value of the crop it attacks, the severity of the disease, and the ease with which it can be controlled.

Diseases that attack the basic food crops, such as the cereals, especially wheat and rice, potatoes, or others according to regional use, are naturally of greatest concern. Epidemics in the chief centers of production can cause scarcity, with serious national and (especially with wheat) international consequences. Prices of the affected crop and of substitutes for it go up. The amount of money available for buying other commodities, whether food or any other, consequently is reduced. It is a chain; in our present national and world economy, no part is separate.

For the farmer, the labor employed in planting and caring for an affected crop is wasted; income is reduced and uncertain.'With epidemic diseases he may suffer disastrous losses in one season. The less variable diseases take a constant toll that in total amount could make the difference between success or failure in the long run. The lesser continual losses may be sufficient to prevent the building-up of reserve for emergencies, and thus the effects of the occasional severe losses are enhanced. The instability of farm income is reflected in the national condition. Losses from plant diseases do not stop when a product is harvested. Fruits and vegetables spoil in transportation, market, and storage. Infection may have started in the field before harvest or it may be acquired later. Whatever the reason, the food supply is further depicted and food bills increased.

If all the that is due plant disease could waste be prevented, it would mean an increase of 10 percent over our present crop production, or, alternatively, lo percent of the land could be used for other purposes or 10 percent of the farm population could engage in other occupations and we would still have as much of everything as we do now.

It should be emphasized that the plant disease situation is always changing. No matter how up-to-date our information, there is always some new problem to meet. Pathogens are as variable in genetic make-up as any other organism, and new races able to attack hitherto resistant varieties of crop plants appear frequently. Wheat stem rust is a familiar example. A crop variety developed for resistance to one pathogen may be extremely susceptible to a previously entirely negligible organism, as happened with the- Victoria blight of oats that flared up so suddenly and destructively a few years ago. Pathogens are carried from country to country in many ways and in spite of careful precautions. Examples of entry into this country are numerous. White pine blister rust is one; potato bacterial ring rot is another.

A grower, noting accounts of disease causing devastation in some other place, may consider that it has nothing to do with him, since crops in his region or his own fields are not affected; perhaps, even, he may rejoice because scarcity has led to higher prices for his own crop. Temporarily he may be justified, but it is never safe for growers or regions to be complacent about freedom of their crops from Plant diseases. To maintain this Position takes constant watchfulness.

If nothing could be done about plant diseases, there would be little point in discussing their importance. We would just have to take the loss and get along with it as best we could. We have seen how that works in some instances. We do know how to reduce the effects of most diseases, however. Increasing our knowledge about diseases will allow us to gain more advantage over them, provided we make use of it. The available control measures are not nearly so often or so efficiently used as they should be.

Diseases are too often taken for granted until irreparable harm has been done. Recognition of their importance is the first step in doing something about them.

JESSIE I. WOOD is an associate pathologist in the Plant Disease Survey, Bureau of Plant Industry, Soils, and Agricultural Engineering. She obtained her master's degree from Stanford University in 1916 and has been with the Department of Agriculture since 1919.

Ergot sclerotic and barley kernels.