Several Fusarium spp. (F. oxysporum, F. avenaceum, F. solani and rarely, F. eumartii) cause wilt diseases in potatoes and yield losses are most pronounced during hot dry seasons. Fusarium wilt is not a major disease in Atlantic Canada.
Wilting and premature death of leaves and vines is caused by vascular infection (browning) particularly in lower stems and roots resulting in yield losses. Fusarium wilts also cause stem end and internal browning of tubers which reduces market quality. The disease can be confused with verticillium wilt but internal stem infection is generally extensive with fusarium wilt while verticillium wilt stem rot is restricted to the vascular system.
Fusarium wilt pathogens remain in the soil for many years but are also in and on seed potato pieces. Three or 4 year crop rotations may not be effective in reducing the level of soil borne inoculum in heavily infested fields. Wilts are most easily observed at high temperatures and dry soil conditions. Roots become infected by fusarium wilt fungi at soil temperature above 20EC. Continual growing of potatoes on infested land leads to inoculum buildup in the soil.
Control
Use seed potatoes free of the wilt pathogen and grow the crop on land that has never grown potatoes or is known to be free of this disease. Avoid contamination of clean fields through transfer of infested soil, diseased tubers or plant residues via crop machinery. Removal of potato vines from fields reduces opportunities for increases in soil borne levels of the fungi. Seed piece treatment fungicides (see Publication No. 1300A) may help control disease levels in infested tubers or on infested land.