The severity of wilt diseases caused by Fusarium oxysporum f.sp. vasinfectum and Verticillium dahliae in cotton is affected by both abiotic and biotic factors. Some of these factors are natural, whereas others are man-made. The natural abiotic factors that affect wilt severity include temperature, soil chemistry and physics, soil moisture (rainfall), and light intensity and duration. The most important aspects of soil chemistry and physics are texture (% sand, silt, and clay), pH, basicity, plant nutrient deficiencies, and toxic ion content (for example, manganese and aluminum). The man-made abiotic factors include various agricultural chemicals, such as lime, fertilizers, herbicides, fungicides, insecticides, and harvest-aide chemicals. The natural biotic factors that affect wilt severity are inoculum density and genotype (or strains) of the wilt pathogen, prevailing weed species, cotton pests (insects, mites, and nematodes), other pathogens, mycorrhizal fungi, and biological antagonists of the wilt fungi. The man-made biotic factors are cultivar selection, crop rotation, and introduced biological antagonists. The timing and methods of various cultural practices, such as planting, cultivation, irrigation, pest control, harvesting, and tillage, have indirect effects on wilt severity by altering the natural abiotic and biotic factors that influence wilts.