How can I manage Fusarium on tomatoes?

T.S.NevadaAnswer: There are different forms of Fusarium disease in tomatoes: Fusarium wilt and Fusarium crown and root rot. Fusarium wilt, caused by the fungus F. oxysporum f. sp. lycopersici (FOL), produces less extensive discoloration in the plant’s water-conducting tissue than Fusarium crown and root rot; the brown streaks extend less than 20 to 30 cm. (8 to 12 in.) above the soil line. Fusarium crown and root rot is caused by the fungus Fusarium oxysporum f. sp. radicis-lycopersici (FORL). Crown and root rot is more likely with cool temperatures (10?C to 20?C/50?F to 68?F), low soil pH (acidic), ammoniacal nitrogen, and water-logged conditions. Since your soils are likely on the alkaline side and generally not waterlogged, it is likely that you have Fusarium wilt (FOL).Crop rotation for 4 to 6 years is a possible control measure for both diseases, but success is not assured. Practice sanitation in the garden by destroying any infected plant debris. The best method of control is to plant resistant varieties. Some Verticillium wilt and Fusarium wilt (VF) resistant tomato varieties are listed below. Better Boy Heinz 1350Beefsteak Roma VFBig Girl RutgersCampbell SpringsetFloramerica SupersonicResearch has shown that non-pathogenic strains of Fusarium oxysporum—particularly Isolate CS-20—can protect against low pathogen innoculum densities (Larkin et al., 1997). CS-20 apparently triggers development of systemic acquired resistance in the infected tomato plant, thereby making the plant more resistant to subsequent infections of pathogenic forms of F. oxysporum. Unfortunately, there are no commercial products available that use the non-pathogenic forms of this fungus at present. Some (but by no means all) commercially available formulations of bacteria or fungi that have shown effectiveness against Fusarium are listed below. Make sure you check with your certifier to learn which products are allowed for use in organic systems.

Product Name/trade name

Active ingredient

Effective Against

Comments on use

Manufacturer

T-22 HC (OMRI* listed), Rootshield, Plantshield, TopShield

Trichoderma harzianum (Rifai strain KRL-AG2)

Fusarium, Rhizoctonia, Sclerotium,  Sclerotinia and Botrytis species.

For preventative control of root diseases. Apply to seed, roots or soil, and can also be applied to foliage for control of fungal diseases.

BioWorks, Inc. 122 North Genesee St. Geneva, NY 14456 315-781-1703 315-781-1793 Fax Toll free: 800-877-9443 chayes@bioworksbiocontrol.com www.bioworksbiocontrol.com

Bio-Trek

Trichoderma harzianum (Rifai strain KRL-AG2)

Fusarium, Rhizoctonia, Sclerotium,  Sclerotinia and Botrytis

For preventative control of root diseases. Apply to seed, roots or soil, and can also be applied to foliage for control of fungal diseases.

Wilbur-Ellis 1801 Oakland Blvd., Suite 210 Walnut Creek, CA 94596 415-772-4000 415-722-4005 Fax Toll Free: 800-500-1698 www.wilburellis.com

Mycostop (OMRI listed)

Streptomyces griseoviridis (S train K61)

Fusarium spp., Alternaria brassicola, Phomopsis spp., Botrytis spp., Pythium spp., and Phytophthora spp.

For preventative control of root diseases. Apply to seed, roots or soil. Particularly effective against Fusarium.

U.S. Distributor: AgBio Development Inc. 9915 Raleigh St. Westminster, CO 80031 877-268-2020, 303-469-9221; 303-469-9598 Fax www.agbio-inc.com

Kodiak ™ (Gufstasen)

Seranade (Agraquest)

Subtilex (Becker Underwood)

Bacillus subtilis

Wide range of foliar and root diseases

Used as seed treatment, biofungicide, inoculant and protectant.

Gustafson, Inc. 1400 Preston Road, Suite 400 Plano, TX 75093-5160 972-985-8877 972-985-1696 Fax www.gustafson.com

AgraQuest, Inc. 1530 Drew Avenue Davis, CA 95616 530-750-0150 530-750-0153 Fax www.agraquest.com E-mail: info@agraquest.com

Becker Underwood, Inc P.O. Box 667 801 Dayton Ave. Ames, IA 50010 515-232-5907 515-232-5961 Fax Toll free: 800-232-5907 request@beckerunderwood.com www.beckerunderwood.com

*OMRI: Organic Materials Review Institute is a 501 (c)(3) nonprofit. Its mission is to provide professional, independent, and transparent review of materials allowed to produce, process and handle organic food and fiber.In combination with applied materials, cultural controls are important components of any sustainable agriculture system. Cultural controls include:+ Use disease-free transplants and seed+ Use planting stock resistant to Fusarium.+ A 5-7 year rotation away from hosts.+ Use nitrate nitrogen rather than ammonium nitrogen. + Use localized fertilizer placement to feed the plants rather than the fungus. + Do not flood irrigate or use pond or ditch water to irrigate. Well water may be preferable, as it’s less likely to contain Fusarium propagules.An effective strategy to help destroy Fusarium innoculum is to solarize your soil. The basic technique entails laying clear plastic over tilled, moistened soil for approximately six to eight weeks. Solar heat is trapped by the plastic, raising the soil temperature and destroying the innoculum. The incorporation of poultry litter prior to solarization, or use of a second layer of clear plastic, can reduce effective solarization time to 30 days. (Brown et al., 1989; Stevens et al., 1990) Brassica residues are also known to increase the solarization effect, in a process known as biofumigation. The plastic holds in the gaseous breakdown products of the brassica crop (or food processing wastes), thereby increasing the fumigation-like effect. (High microbial activity has been reported to suppress Fusarium wilt, so maintaining healthy soils with sufficient organic matter to support high microbial populations is another form of cultural control. A University of California Cooperative Extension leaflet (No. 21377), “Soil Solarization: A Nonchemical Method for Controlling Diseases and Pests,” details the technique: ANR Publications, University of California.6701 San Pablo Ave.Oakland, CA 94608-1239 510-642-2431; 800-994-8849www.anrcatalog.ucdavis.eduThe Web site www.uckac.edu/iwgss provides links to current research and publications on solarization.References:Borrero, C., M.J. Infantes, E. Gonz?les, M. Avil?s, J.C. Tello. Relation Between Suppressiveness to Tomato Fusarium Wilt and Microbial Populations in Different Growth MediaBrown, J.E. , M.G. Patterson, and M.C. Osborn. 1989. Effects of clear plastic solarization and chicken manure on weed control. p. 76?79. In: Proceedings ofthe 21st National Agricultural Plastics Congress. Nat. Ag. Plastics Assoc., Peoria, IL.Gamliel, A., and J.J. Stapleton. 1993. Characterization of antifungal volatile compounds evolved from solarized soil amended with cabbage residues. Phytopathology. Sept. p. 899?905.Larkin, R. P. and D. R. Fravel. 1997. Biological Control of Fusarium Wilt of Tomato Under Varying Environmental Conditions.www.epa.gov/ozone/mbr/airc/1997/036larkin.pdfRoberts, P. D., McGovern, R. J., and L.E. Datnoff. 2001. Fusarium Crown and Root Rot of Tomato in Florida. Plant Pathology Department, Florida Cooperative Extension Service. Publication PP-52. http://edis.ifas.ufl.edu/PG082Stevens, C., V.A. Khan, and A.Y. Tang. 1990. Solar heating of soil with double plastic layers: a potential method of pest control. p. 163?68. In: Proceedings of the 22nd National Agricultural Plastics Con gress. Nat. Ag. Plastics Assoc., Peoria, IL.