Of all the food produced in the world one third is lost to insect pests, weeds and diseases, and the total world population is estimated as growing from 4000 million in 1975 to about 6000 million by the year 2000. To satisfy these needs, the world's farmers must meet the extra requirement every year. The easiest way in which farmers can increase the amount of food they produce is to prevent the loss due to pests. The biological control measures which were once thought to be the safest methods of pest control have, as we now know, not proved successful on a commercial scale. In such a dismal...