See:
Cucumber (Cucumis sativus) - Fusarium Crown, Foot and Fruit Rot
Cucumber (Cucumis sativus) - Fusarium Wilt
Cucumber (Cucumis sativus) - Verticillium Wilt
Cause The fungus, Fusarium oxysporum f. sp. radicis-cucumerinum, which is a more recent disease problem on cucumber and melon in greenhouse production. This fungus may persist for more than a year in plant debris and soil as durable spores (chlamydospores) or in association with organic matter. Seed transmission has not been reported but may be possible. Movement of contaminated organic matter, soil, or transplants can move the pathogen longer distances. The pathogen can be transported shorter distances by wind, water, and the adult form of the fungus gnat. Wounding of tissue facilitates root infection, including feeding by plant parasitic nematodes and transplant injuries. The fungus can also infect aboveground through pruning injuries or other wounds. Cooler temperatures (62ºF to 66ºF) and adverse growing conditions promote disease.
Symptoms Symptoms typically appear once fruit development is underway. Younger plants, but not seedlings, first develop a light green to brown rot of the lower stem, usually on one side. The stem lesion continues to grow and pinkish-white mycelium appears. Secondary infections by bacteria can occur. Rot of the taproot and secondary roots develops. The vascular tissue at the base of the stem may be discolored. Plants are stunted, may wilt and die within a month, but fruit rot is not observed.
Cultural control
- Graft scions onto resistant rootstock (Cucurbita maxima x C. moschata).
- Use laboratory-tested pathogen-free seed and clean transplants.
- Treat seed with hot water or steam treatments.
- Practice good sanitation in greenhouse production, including of tools and equipment, pots, trays, and irrigation lines.
- Rogue infected plants to reduce spread in the greenhouse.
- Remove and destroy plant residues from the greenhouse after harvest.
- Do not reuse growing media unless it has been steam-sterilized.
Chemical control
- Seed treatment may reduce disease caused by seedborne propagules.
- Treat seed with Maxim 4FS (Group 12) 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
- Bexfond at 7 to 28 fl oz/A. 4-hr reentry. O
- Double Nickel LC at 1 to 2 quarts/A as a banded soil spray or drench on 4- to 6-week intervals or at 0.5 to 4.5 pints/A on 2- to 4-week intervals. 4-hr reentry. O
- Rootshield WP at 3 to 8 oz/100 gal water for greenhouse soil drench and field chemigation or at 16 to 32 oz/A as in-furrow spray. 4-hr reentry. O
- SoilGard at 2 to 10 lb/A at 4-week intervals will suppress Fusarium. See label for specific application types and timings. 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
Reference Keinath, A.P., Wintermantel, W.M., and Zitter, T.A. 2017. Compendium of Cucurbit Diseases and Pests, 2nd Ed. St. Paul, MN: APS Press