Yet a comprehensive analysis of how climate change would influence the dissemination of plant diseases and impact the primary production in most agricultural ecosystems is at the moment missing. There are hardly any studies on the impacts of climate change on the dissemination of diseases in field crops. Multifactor studies under realistic in situ field situations ecosystems are a way forward. No doubt, the realistic assessment of CO2 free air or air enriched with increasing CO2 and O3 concentrations always incorporating spectral reflectance measures on plant growth. Ecologists are now addressing the role of plant disease on the varied ecosystem processes and the challenge of scaling up from individual infection probabilities to epidemics and broader impacts. Plant diseases are considered an important component of plant and environmental health that might be arise through either infection with biotic pathogens as well as abiotic factors. Biotic plant diseases are caused by organisms such as fungi, bacteria, viruses, nematodes, phytoplasmas as well as with parasites. Abiotic diseases, on the other hand, are for all time associated with chemical and physical climatic factors, such as temperature or moisture extremes, farming factors such as nutrient deficiencies, mineral toxicities and pollution. At the genomic level, advances in technologies for the highthroughput analysis of gene expression have made it possible to begin discriminating responses to different biotic and abiotic stressors and potential trade-offs in responses. Most plant diseases models use deferent climatic variables and operate at a deferent spatial and temporal scale than do the global climate ones. The current review describes environmental factors that influence severity of crop disease epidemics in order to assess the predicted impacts of climate change on plant growth and their harvest as well as on the severity of disease epidemics. Effects of a changing climate on chemical and biological controls of plant diseases are also discussed in the context of the changing global outlooks on environmental demands for the future.
