The former occurred because the success ful control of insect pests with insecticides in the 1950s and 1960s allowed plant breeders to concentrate on developing new high yielding cultivars in the safe know edge that the insects were taken care of cheaply and effectively with insecticides. Hence, the breeders focused their attention more on attaining outstanding yields than on producing insect resistant(Ferro 1987). Insect outbreaks then occurred on cultivars having no natural levels of insect resistance when the insecticide umbrella was removed(brought about by insects resistant to insecticides)