The infection of young seedlings may result in the wilting and necrosis of cotyledons and occasionally, plant death. This creates an uneven stand in the field, a pattern that may be confused with seedling diseases such as damping-off caused by Pythium spp. and Rhizoctonia spp. Internal symptoms of FOV infection include brown discoloration in the vasculature. Plants infected at a later stage of growth may be wilted and stunted, and leaves may display chlorosis and necrosis. The characteristic brown vascular discoloration is most evident in the roots and lower stem, but may be apparent in upper branches as well.
Disease foci increase in size through the redistribution of infested soil and plant material by field equipment and water. The rate at which these foci expand and coalesce is dependent upon a combination of environmental factors such as the susceptibility of the cultivar, inoculum density, soil texture and pH (Hao et al., 2009, Mundkur, 1936 and Wang et al., 1999b). Estimated average crop losses due to seedling diseases including Fusarium wilt in the United States are 2.85% per year; losses due to Fusarium spp. specifically are about 0.35% ( National Cotton Council of America).