Fusarium spp. are soil-borne fungal pathogens that affect many crops. Fusarium infects plant roots and crown, infecting cortical tissue and when reaches the vascular system it interrupts sap flow inducing wilting. Symptoms are dry root rot, damping off, stem collapse, leaf yellowing, wilting, and death. Fusarium persists in the soil mainly in plant debris and can be seed-transmitted. Fusarium spp. produce typical microconidia, macroconidia and chlamydospores (inoculum) that can infect plant tissue. Chlamydospores can overwinter/survive in the soil as well as wooden and other surfaces. Many crops and weeds are susceptible to Fusarium spp. and are the source of inoculum for infection of tomato and other crops.
Fusarium crown and root rot (Fusarium oxysporum f. sp. radicis-lycopersici) is a problem in many solanaceous crops, including tomatoes, in greenhouse and field production. Infection and disease development is favored by cool temperatures (60-70°F). Fusarium crown and root rot infects the cortical tissue through wounds and natural openings inducing a dry lesion with a distinctive chocolate-brown discoloration. The internal discoloration of the cortex tissue and cambium can extend 2 to 4 inches up from the lesion at the base of the plant (Figure 1). In mature plants, the margin of lower leaves may turn yellow and develop into necrotic tissue (Figure 2). Plants may wilt, especially on hot days, and become stunted. Eventually, fungal structures such as white mycelium and spores appear in lesions, necrotic tissue and debris. Microconidia of Fusarium oxysporum f. sp. radicis-lycopersici, however, are airborne, which facilitates infection of surrounding healthy plants and reinfestation of steamed soil, especially in high tunnels and greenhouses.
Fusarium crown and root rot: internal discoloration of the cortex and cambium. (source: R.A. Arancibia)
Fusarium crown and root rot foliar symptoms: lower leaves with marginal necrosis. (source: R.A. Arancibia)
Fusarium wilt (Fusarium oxysporum f. sp. Lycopersici) is another important soilborne disease of tomato, and other solanaceous crop that is favored by warm temperature (82°F). It also infects through wounds, but invades and clogs the vascular system (xylem) reducing or stopping the flow of sap, which induces wilt. There are three identified races (races 1, 2, and 3), all present in tomato production areas in the United States. Many tomato cultivars have been developed with resistance to races 1 and 2, but only a few with resistance to race 3. Fusarium wilt symptoms in high tunnels and greenhouses may start with bright yellowing of bottom leaves that may continue to the length of the plant (Figure 3). In mature plants, it induces yellowing and wilting usually after flowering (Figure 4). The initial symptoms of yellowing may appear on one side of the leaf and/or plant (Figures 3 and 4), then develop into chlorosis and wilting of the entire plant. Internally, the vascular system (xylem) turns reddish-brown (Figure 5) and can extend the length of the plant.
Fusarium wilt foliar symptoms: yellowing on leaves in one side of the plant. (source: R.A. Arancibia)
Fusarium wilt foliar symptoms: yellowing on one side of the leaves and wilting and stunting of the entire plant. (source: R.A. Arancibia)
Figure 5. Fusarium wilt: vascular tissue (xylem) discoloration. (source: R.A. Arancibia)
Fusarium foot rot (Fusarium solani f. sp. eumartii) in tomato is a minor disease, but it can kill the plant. It induces reddish-brown lesions in the cortex of taproot and large secondary roots and is associated with vascular discoloration. As the disease further develops, these lesions may encircle the root, and the entire plant may die. Meanwhile, leaves may show interveinal chlorosis and necrosis during the growing season. The optimum growth temperature of isolates from California is 77-86°F. There is no resistant cultivars, so the only control method is sanitary practices to avoid its introduction and limit its spread.
Management
The first and most effective practice to manage Fusarium spp. is the use of resistant cultivars, however, many growers and consumers prefer heirloom cultivars are not resistant to diseases. Even when using resistant cultivars, cultural practices to reduce inoculum (micro and macroconidia and chlamydospores) and Fusarium incidence should be considered to minimize the risk of developing Fusarium races that may overcome cultivar resistance. Sanitary practices include reducing inoculum by pulling and burning diseased plants and not reincorporate them into the soil or compost, preventing conditions for diseases to become established (soil drainage and raised planting beds or 10-15 inches ridged rows), and those that modify the environment to reduce infections and disease incidence (planting site, soil, tillage, crop rotation, wind breaks, and good irrigation practices to avoid soil saturation). Biological agents (microorganisms attacking pathogens) incorporated into the soil have been identified and their effectiveness in reducing Fusarium incidence have been evaluated by several research institutions. Commercial products containing these biological agents are available and registered in the OMRI list for organic production and for conventional production as well. A list of several commercial products, the active ingredient, and target disease can be found in Gauthier, N., et al. (see Literature resources)
Literature resources:
Davis, R.M. and A.O. Paulus. 2014. Fusarium crown and root rot. In: Compendium of tomato diseases 2nd Edition, J.B. Jones, T.A Zitter, T.M. Momol, and S.A. Miller. (Editors). The APS press, 3340 pilot Knob Rd. St. Paul, Minnesota.
Davis, R.M. and A.O. Paulus. 2014. Fusarium foot rot. In: Compendium of tomato diseases 2nd Edition, J.B. Jones, T.A Zitter, T.M. Momol, and S.A. Miller. (Editors). APS press, 3340 pilot Knob Rd. St. Paul, Minnesota.
Correl, J. and J.P. Jones. 2014. Fusarium wilt. In: Compendium of tomato diseases 2nd Edition, J.B. Jones, T.A Zitter, T.M. Momol, and S.A. Miller. (Editors). APS press, 3340 pilot Knob Rd. St. Paul, Minnesota.
Gauthier, N., H. Smith, K. Leonberger, and S. Geurkink. Organic disease management guide for specialty crop production. Plant Pathology Fast Facts, University of Kentucky. https://plantpathology.mgcafe.uky.edu/sites/plantpathology.ca.uky.edu/files/Organic_Disease_Mgmt_PPFS-FF.pdf Retrieved May 28, 2026.