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Fusarium wilt (Fusarium oxysporum) primarily affects watermelon but can occur less commonly on melons and cucumber. Symptoms include stunting, yellowing, and wilting of plants. Early on, individual runners wilt, and later the entire plant will collapse. Wilted plants may recover at night but gradually decline and die. Vascular tissue from the crown and lower stem will be discolored (brown) when cut and examined.

Fusarium wilt vascular discoloration.

(Photo: David Lanston, University of Georgia, Bugwood.org)

Fusarium wilt symptoms in melon planting.

(Photo: Howard Schwartz, Colorado State University, Bugwood.org)

Management:

• Crop rotation (limited effectiveness)
• Control of nematodes (wounds on roots caused by nematode feeding can be invaded by Fusarium)
• Sanitation (avoid spreading contaminated soil)
• Planting of resistant varieties. Watermelon, melon, and cucumber are affected by different formae speciales (groups adapted to a specific host), and each of these groups have different pathogenic races. In the case of watermelon (caused by F. oxysporum f.sp. niveum), there are three races—0, 1, and 2. Good resistance is available to races 0 and 1 but not race 2. In Kentucky, thus far, race 2 has not been reported. Muskmelons are affected by F. oxysporum f.sp. melonis, which has four known races (0; 1; 2; and 1,2); race 2 is the most widely distributed in the United States, and resistant varieties are available to races 0, 1, and 2. Three races of F. oxysporum f.sp. cucumerinum affect cucumbers; race 1 is the most common in the United States.

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