Cause Fusarium F. oxysporum f. sp. radicis-lycopersici, a fungus that lives in soil and can cause rot of the below-ground portions and subsequently plant wilting. Disease is favored by cool, wet soils, a low soil pH, and ammonium nitrogen. F. oxysporum f. sp. radicis-lycopersici can survive several years in soil and can be spread by infested equipment, infected transplants, and windborne or waterborne infested soil. Tomato seed has been reported to be contaminated with this pathogen. Hardware and structure portions can be contaminated or infested by the fungus; this fungus has been recovered from plastic and wooden stakes as well as greenhouse walls and support poles. Shore flies (Scatella stagnalis) and fungus gnats (family Diptera) have been reported to transmit this fungus to healthy plants if diseased plants are nearby. Disease can spread within a planting by infected root contact between plants and through irrigation water.
Although this fungus causes disease specifically on tomato, it may colonize the roots of nonhosts in the absence of any symptoms, although sometimes infections will result in the development of symptoms. Plant families and species besides tomato that can be infected by this fungus include: Brassicaceae (Brassica juncea, B. oleracea), Cucurbitaceae (watermelon), Leguminosae (fava bean, snap or dry bean, pea, peanut, soybean, and clovers), and Umbelliferae (celery, carrot) as well as weedy plants such as plantain (Plantago lanceolate), carpetweed (Mullugo verticillata), Queen Anne's Lace (Daucus carota) and Shepherd's purse (Capsella bursa-pastoris).
Symptoms Lower leaves yellow and plants wilt during the hot part of the day, especially during flowering, but may recover in the evening until disease becomes more advanced. Eventually the leaves remain wilted, shrivel, turn brown, and die; the entire plant can die. Rot symptoms on the tap root and the lower stem at the soil line are typical, sometimes a vascular discoloration may be found along the bottom 1-ft portion of the main stem. Can be confused with Fusarium wilt. Damping-off of young seedlings may be observed.
- Use resistant varieties or resistant rootstock if grafting.
- Remove and destroy all affected plant tissue, including roots.
- Thoroughly clean propagation equipment, especially if reusing plant trays and pots.
- Clean soil from equipment including machinery, footwear, gloves, etc., after working in an affected planting.
- Manage for shore flies and fungus gnats inside greenhouses, especially if propagating tomato.
- Rotating out of tomatoes 4 to 6 years may reduce losses.
- OSO 5% SC (Group 19) at 3.75 to 13 fl oz/A on 7- to 14-day intervals. Can be applied the day of harvest. 4-hr reentry. O
- Prestop as a soil drench or incorporation into growing medium. 4-hr reentry. O
- Regalia (Group P5) at 1 to 2 quarts/A as an in-furrow treatment. Does not benefit from the addition of an adjuvant. 4-hr reentry. O
- Stargus at 6 to 8 fl oz per 1,000 ft row as an in-furrow treatment, or 3 to 4 quarts/A as a soil drench (drip or chemigation) on 10- to 21-day intervals. Preharvest interval is 0 days. 4-hr reentry. O
Reference McGovern, R.J. 2015. Management of tomato diseases caused by Fusarium oxysporum. Crop Protection 73:78-92.