The white (Irish) potato probably is one of the most important food plants in the world today. Grown almost everywhere the climate is suitable, it is a top source of carbohydrates, vitamins, iron, thiamin, niacin, and is less fattening than most other foods in the daily diet.

The serious problem with the potato has been the many diseases to which it is susceptible, particularly blight. Blight can completely ruin a crop in a very short time. Years ago growers found it difficult to tell when blight might strike, so they sprayed against it every 5 to 7 days, up to 16 times a season. Such spraying was costly and put excessive fungicide into the environment.

Now there is reason to expect that much of this spraying can be eliminated.

Things began to change in the mid-1960s when Penn State University, funded by the Department of Agriculture, offered blight forecasting to a limited number of growers.

Each grower had to buy a hygrothermograph to record temperature and humidity in his fields, and then mail the information to the University. Potential blight conditions were evaluated, and a spray program recommended. This has to be done for each grower because weather conditions that determine the likelihood of blight vary from location to location.

In 1970, the program was computerized, letting a grower phone data and receive a recommendation in under three minutes. The program, called Blitecast, was fairly effective, although errors did creep in. But the main problem was expense because the university had to hire someone to do the computer work.

In 1977, Penn State's Argricultural Experiment Station funded Dr. David R. MacKenize, Penn State plant pathologist whose research focuses on breeding better varieties of potatoes and preventing disease, to design an on-site microcomputer that would collect and analyze weather information and then make a spray recommendation.

MacKenzie enlisted four electrical engineering students and one computer science student who in six months designed a unsable system.

Working independently on a similar project was a Utah engineering firm. MacKenzie supplied the Utah company data and knowledge developed at Penn State, which resulted in a production computer called Blitecaster, being marketed (it can be purchased from Campbell Scientific, P.O. Box 551, Logan, Utah 84221).

The box (computer) sits in or near a potato patch, it samples the surroundings every 10 minutes, day and night, rain or shine, recording temperature, relative humidity, and rainfall. When a button in its housing is pressed, the box tells whether to spray the fields to protect them from the devastating blight.

Mr. and Mrs. William Frederick of Sugarloaf, R.D. Luzerne County, used a unit last summer and had no blight. "It gives you plenty of warning to get ready for spraying," Frederick says. They calculate the Blitecaster eliminated four sprayings of their 150 acres of potatoes and estimate the savings as $2,400.

The Blitecaster costs around $1,000. MacKenzie says an individual farmer must have at least 50 acres of potatoes to justify a Blitecaster. A less expensive alternative system is being tested.

It is expected that other plant diseases will probably be programmed in the near future and the box (Blitecaster) may forecast aphid damage to potatoes, scab diseases of apples, and leaf spot diseases of peanuts.