CHAPTER 15 - APHIDS, VIRUSES, AND THE YELLOW PLAGUE

Abstract

This chapter discusses aphids, viruses, and the yellow plague. The general acceptance of the yellowing diseases as being induced by natural factors has plagued man since the dawn of agriculture. Diseases that occasionally break out with explosive force are less dangerous in many ways than the diseases are accepted as inevitable or normal. The general acceptance of the yellowing diseases as being induced by natural factors has plagued man since the dawn of agriculture. The yellowing diseases in areas such as the Salinas Valley of California have been ubiquitous for as long as can be remembered. The distinction between diseased and disease-free crops was not observed for many years and thus, the diseased crops were regarded as normal and there was no incentive to investigate the losses induced by these omnipresent diseases. The development of virus-resistant varieties offers additional possibilities in the control of the losses caused by virus yellows. The common occurrence of the yellows viruses on a large number of plant species, and the intricate biological relationships of the viruses with their hosts and vectors have both played a major role in the great variability of this virus group. The true relationships of a few members of the complex are now known. The determination of the relationships of other members of the complex with different host ranges and vector species is a challenge.