Causal Agent:
Fusarium oxysporum f. sp. cucumerinum on cucumber. 
Fusarium oxysporum f. sp. melonis on cantaloupe; four races are known. 
Fusarium oxysporum f. sp. niveum on watermelon; three races are known.

Distribution:
Worldwide; although some races are not widely distributed.

Symptoms:
Cucumber, cantaloupe and watermelon each are susceptible to specialized strains of the fungus. In young, infected seedlings cotyledons begin to droop and quickly turn yellow. Damping off may sometimes occur. Older tissue then turns brown as the entire plant wilts and dies. In older plants often one branch will first begin to wilt. This is followed by progressive wilting of the entire plant and finally death. A girdling at the hypocotyl area, as well as stunting of the plant may also occur. In cantaloupe and watermelon, a dark brown streak which begins at the soil line often develops on one side of the vine. A section through the base of the plant will reveal a yellow, orange or brown discoloration in the water conducting tissues. 

Conditions for Disease Development:
The fungus causing Fusarium wilt can survive in soil for many years. Infested soil on farm machinery, infected crop debris, wind-blown soil and irrigation water all may result in movement of the fungus from field to field. The fungus enters the plants through the roots and the disease develops quickly when soil temperatures are warm.

Control:
Use resistant varieties. Plant in fields not infested with the organism. Adjusting soil pH to 6.5 and using nitrate nitrogen can inhibit disease development in infested fields. Prevent infesting new areas by steam cleaning equipment.