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Significance

By the standards of modern agriculture, the tomato and potato are relatively recently adopted crops. Wide scale cultivation gained prominence largely in the 19th century some 300 years after their introduction into Europe from the Andean region of South America. The tomato was initially considered a horticultural crop, but the development of the food processing industry and its appetite for large quantities of cheaply produced tomatoes lead to the development of large scale field production of tomatoes particularly in the U.S. Worldwide production of this crop in 2000 was approximately 98 million metric tonnes. The potato is a dietary staple in nearly all temperate countries with annual production worldwide in 2000 of around 311 million metric tonnes.

Early blight is distributed worldwide and essentially occurs wherever tomatoes and potatoes are grown. In the U.S. early blight in tomatoes can be problematic east of the Rocky Mountains but is not usually a problem in the less humid inter-mountain or Pacific regions. Uncontrolled, the disease may cause severe defoliation resulting in reduced fruit size and number. In potatoes the disease occurs in most production areas to some degree every year although it has a significant effect on yield only when frequent wetting of the foliage favors early and rapid symptom development.

Estimating total annual crop losses to any one particular disease is difficult to do accurately. Values in the literature for measured crop losses due to early blight in nonsprayed fields vary enormously from 5 - 78%. Precise figures for total expenditure on fungicides for control of early blight is also difficult to determine due to the fact that it is just one of a complex of tomato/potato pathogens which are normally controlled with the same products. Best estimates suggest annual expenditure globally on fungicides for control of Alternaria spp. is around $32 million in tomatoes and $45 million in potatoes.

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