Suppression of Soilborne Phytopathogenic Fungi of Tomatoes via Integrated Production Systems that Utilize Biofumigation, Composted Amendments, Solarization, and Chemical Fumigants.

View the project final report

• 2001 annual report

Commodities

• Vegetables: tomatoes

Practices

• Crop Production: biological inoculants, cover crops, fertigation, application rate management, strip tillage, tissue analysis
• Education and Training: demonstration
• Pest Management: biological control, botanical pesticides, chemical control, competition, integrated pest management, mulching - plastic, prevention, row covers (for pests), soil solarization
• Production Systems: holistic management
• Soil Management: green manures, soil analysis, organic matter

During the growing seasons of 2001 and 2002 field studies involving sustainable pre-plant treatments for use in plasticulture tomato production were trialed. Compost based treatments were found to be effective at both increasing yields and decreasing the incidence of Southern Blight. Biofumigation treatments also favorably influenced crop production although they were not as effective as synthetic fumigants. Low-dose chemical fumigation, when combined with organic amendments, proved to be a feasible alternative to full dose fumigation. Solarization treatments were implemented during the spring and did not significantly suppress soilborne diseases.

Introduction

The use of raised-bed plasticulture systems for fruit and vegetable production is becoming increasingly prevalent within the United States. Advantages include increased crop performance by conserving moisture and nutrients, stabilizing soil temperature, reducing some diseases, reducing or eliminating weeds, and increasing early-harvest yields (Jaworski, 1981). This production method is commonly used for field tomatoes (Lycopersicon esculentum Mill.) - an economically important agricultural industry in many states. Tennessee is the fourth largest tomato producer in the United States (based on 5,700 production acres reported by Rutledge, 1998; USDA, 1998). Tomato production in surrounding southeastern states represents almost 20,000 production acres.
Often grown without rotation, tomato fields can develop high pathogen inoculum densities. Southern Blight, caused by the phytopathogenic fungus Sclerotium rolfsii, represents one of the major disease threats to tomato crops in the southeast United States. This pathogen is also a hazard to many other agricultural investments throughout the U.S. making the investigation of pre-plant soil treatments for plasticulture tomato production under pressure from Southern Blight an important area of research.
Methyl bromide fumigation has routinely been heavily relied upon for pathogen management in modern high production raised-bed agriculture. There is an accumulation of experimental data supporting the concept that many non-chemically based pest management strategies are effective in controlling diseases caused by soilborne pathogens. The mode of action of many of these treatments has also been described. Composted amendments can introduce a varied microflora into soil ecology, including many biocontrol agents, while providing a suitable substrate to support their growth (Hoitink, 1994). Macerated tissues from Brassica cover crops are known to release biocidal compounds that are able to suppress soilborne pathogens when incorporated into the soil (Kirkegaard, 1998). Solarization has also been shown to reduce pathogen numbers by elevating soil temperatures to levels that deactivate their propagules (Katan, 1991). Sustainable control of soilborne phytopathogenic fungi is likely to be achieved through the enhancement of alternate control methods via the integration of multiple techniques (Cook, 1990). Sub-lethal doses of chemical fumigants can act to weaken pathogen propagules making them more susceptible to the actions of the microbial antagonists that can be delivered through compost applications. Similarly, the heating of soilborne sclerotia via solarization increases their chance of colonization by bacteria (Lifshitz, 1983).
The SARE-funded graduate research project based at The University of Tennessee investigated the methods required to successfully implement the various sustainable management techniques described above.

1. Determine the most effective biofumigation practices for controlling Southern Blight in tomato.
2. Determine the optimal composting system for enhancing yields and controlling soilborne pathogens.
3. Examine the efficacy of combining chemical fumigants with organic amendments.
4. Develop an integrated system of sustainable disease management that combines biofumigation, composting, and solarization in addition to, or exclusive of, synthetic chemical fumigants.
5. Prepare the model system for implementation in commercial tomato production.