Major Signs and Symptoms Caused by Biotic and Abiotic Agents on Plants in the Tropical Africa

There exist two classes of plant diseases, those caused by living microbes also termed biotic or infectious and those caused by non-living agents also referred to as abiotic or non-infectious and include damage from air pollution, nutritional deficiencies or toxicities. Diseases, regardless of class exacerbate crop loss and consequently contribute to food insufficiency in tropical Africa. In order to identify and develop strategies to combat the disease-causal agents (DiCA), it is necessary to understand and appropriately differentiate the signs and/or symptoms (SoS) to avoid wrong or inappropriate use of resources including reagents, time and equipment on wrong disease-causal targets. It is most obvious that biotic DiCA populations are variable in genotype, time and space, and can evolve, but a number of SoS are likely to be evenly or slightly unevenly the same. Thus, this review discusses basic characteristic SoS caused by the DiCA in the tropical Africa. The region has been focused due to existence of different interactive factors in the plant-disease environments all of which cause confusion in the differentiation of the SoS. This information will be used by agricultural extension staffs and crop producers in taking ideal steps towards plant disease control, and lower and higher career phyto-pathologists in deciding and justifying proper detection, characterization and identification methods of responsible biotic or abiotic factors.