Fusarium Rot of Cucurbits
Pest Management Fact Sheet #5093
Fusarium solani f.sp. cucurbitae causes foot, root, stem, and fruit rot of cucurbits. At least two races are known, one of which attacks only the fruit (Race 2) whereas Race 1 can attack the root, foot, stem, and fruit. This disease tends to be most serious on squash and pumpkin but other cucurbits are also susceptible. Although it is not a common disease, it has been found in Maine and it can cause significant crop loss.
There is no clear indication of the environmental conditions which are necessary for this disease. The plant can be attacked at any time following seed germination. Conditions which discourage rapid germination and growth, such as cool wet soil, are likely to favor the disease. It is also suggested that Fusarium may follow other injuries such as fertilizer injury or drought.
Early symptoms may appear as a damping-off where young plants fall over and die. As the season progresses the disease may be expressed as stunting and sudden wilting may occur during hot dry weather because the rotting stem cannot transport sufficient water to the plant. The disease appears as a distinct brown decay at the base of the plant at the soil line. During wet weather the decay may turn soft and mushy and extend up the plant but dry weather may mask the infection as the decay remains below the soil. A white to pinkish growth may be evident when sufficient water is available.
Fruit may also be infected and the infection usually begins on the soil side. Fruit infections appear circular although multiple infections may merge and obscure concentric patterns. Fusarium fruit rot is usually firm and dry although secondary organisms may invade and cause a wet rot.
Survival and Dispersal
This fungus is soil-borne but it can also be carried by the seed. Seed transmission rates of 100% are possible. The fungus can survive up to three years in the soil or the seed. Spores of the fungus are produced on the infected plant material and can be transported by rain splash, running water, cultivation, and any other practice which transports soil around the field. The heaviest concentrations tend to be where infected plants were previously grown.
Effective control of this disease relies on elimination of the fungus. This means using clean seed which is planted in uninfested soil. A three year rotation is probably sufficient to control the disease but a four year rotation may be advisable where problems have been severe. Hot water treatment of the seeds can help to clean them up (132°F for 15 min.) although reduced seed viability should be expected. In the greenhouse, sterile soil should be used. There are no resistant varieties available and there are no effective fungicides.
When Using Pesticides
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Pest Management Unit
Cooperative Extension Diagnostic and Research Laboratory
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