Diseases are a major source of crop and plant damage that can be caused by a number of plant pathogenic (disease-causing) organisms. Fungi are the number one cause of crop loss worldwide. Viruses, nematodes, and bacteria also cause diseases in plants (Figures 1, 3, 4). Symptoms resembling those caused by pathogens can be caused by abiotic (non-living) factors, such as nutrient deficiency and air pollution