Cause Fusarium oxysporum f. sp. radicis-cucumerinum is a problem in cucumbers, especially in greenhouse crops. It has been reported in Canada and western Europe. Cantaloupe and watermelon are susceptible to this fungus in Canada while squash and pumpkin are more tolerant. The fungus can survive at least 3 years as chlamydospores in soil or plant debris, or longer by growing on the roots of other plants. It can also colonize rockwool. It can spread by irrigation lines and likely can infect seeds. Plants at any stage of growth can be infected but older plants are less susceptible. Cooler temperatures (62-68°F) favor infection and disease development.
Symptoms Symptoms typically appear once fruit development is underway. Wilting occurs and death of the affected plant may soon follow, leading to unripe fruit or sunburn, and yield loss. Affected plants may have a pinkish to orangish fungal growth on the lower stem. Secondary infections by bacteria can occur.
Cultural control
- Plant resistant varieties.
- Grafting onto resistant rootstocks can reduce problems with this disease.
- Transplant only healthy looking plants.
- Practice good sanitation in greenhouse production, including of tools and equipment, pots, trays, and irrigation lines.
- Do not reuse growing media unless it has been steam-sterilized.
- Treat seed with hot water or steam treatments.
- Rotate out of cucumber and other cucurbits for 4 years.
Chemical control
- Seed treatment may reduce disease caused by seedborne propagules.
- Treat seed with Maxim 4FS at 0.08 to 0.16 fl oz/100 lb seed plus a dye. Controls pathogenic Fusarium and Rhizoctonia spp. Treating weak or damaged seed may reduce germination and/or seed and seedling vigor.
Biological control Efficacy in the Pacific Northwest is unknown.
- Actinovate AG at 3 to 12 oz/A as a soil drench at planting. 4-hr reentry. O
- Actinovate Lawn & Garden at 0.5 to 1 teaspoon/gal water. H O
- Bexfond at 7 to 28 fl oz/A. O
- Double Nickel LC at 0.5 to 4.5 pints/A as a soil drench at planting. 4-hr reentry. O
- Prestop WG as a soil drench or incorporation into growing medium. 4-hr reentry. O
- Rootshield WP at 3 to 5 oz/100 gal water for greenhouse soil drench and field chemigation or at 16 to 32 oz/A as an in-furrow spray. 4-hr reentry. O
- SoilGard at 0.5 to 10 lb/A at 4-week intervals will suppress Pythium and Rhizoctonia. See label for specific application types and timings. Can be applied on the day of harvest. 4-hr reentry. O
- Stargus at 3 to 4 quarts/A as a soil drench on 10- to 21-day intervals. Preharvest interval is 0 days. 4-hr reentry. O
- Taegro 2 at 2.6 to 5.2 oz/A applied as a drench, in-furrow at planting, or through drip irrigation. 4-hr reentry. O