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

2001 Annual Report for GS01-011

Project Type: Graduate Student
Funds awarded in 2001: $10,000.00
Projected End Date: 12/31/2002
Region: Southern
State: Tennessee
Graduate Student:
Major Professor:
Carl Sams
The University of Tennessee

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

Summary

Field studies involving plasticulture tomato production demonstrated that biologically based pest management strategies were effective at controlling southern blight. All plots that utilized biofumigation, composts, or solarization produced higher yields and displayed lower incidence of disease than controls. However, it was the treatments that integrated pathogen control techniques that were the most effective. A pre-plant soil treatment consisting of compost incorporation followed by low-dose soil fumigation with methyl isothiocyanate was more effective at suppressing plant disease than full dose soil fumigation.

Objectives/Performance Targets

1. Determine the most efficacious biofumigation practices for control of soilborne pests of tomato.
2. Determine the optimal composting types and rates of application that most effectively suppress soilborne pathogens.
3. Examine effectiveness of alternate chemical fumigants.
4. Develop integrated system of sustainable disease management that combines biofumigation, composting, and solarization in addition to, or exclusive of synthetic chemical fumigation.
5. Test the most promising integrated production systems in cooperation with commercial tomato growers.

Accomplishments/Milestones

The biologically based pest management techniques, namely biofumigation, composted amendments, and solarization, have been tested for their efficacy in the field and in the greenhouse. Two types of compost, spent mushroom substrate and poultry waste compost were examined and the most effective combination and rate of application was determined. Several varieties of Brassicas were trialed for their ability to act as successful cover crops for biofumigation. Additionally, various planting and incorporation dates have also been tested in order to develop the most effective biofumigation regime. Several methods of solarization were tested including pre-plant and post-harvest applications. During the growing season of 2001 replicated field trials were conducted employing the treatments that had been developed. Mechanically formed plasticulture tomato beds were arranged into thirty separate rows. The plot consisted of ten replicated experimental treatments, including controls, in a randomized block design. Yield data was collected throughout the season and disease incidence recorded. Soil samples were collected in order to conduct microbial enumeration. A database was formed and statistical analysis conducted. Field plots will be established again in 2002. Integrated soil treatments will be implemented after consideration of the 2001 data analysis. The information gained from the two field seasons will enable the development of an effective integrated production system based on principles of sustainable agriculture. Coordinations will be made with local vegetable producers with the goal of trialing the system on large-scale commercial plots.

Impacts and Contributions/Outcomes

The use of raised-bed plasticulture methods for fruit and vegetable production is becoming increasingly prevalent within the southern 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. Hence, research focusing on disease prevention methods applicable to this commonly used method of agricultural production is essential. Often grown without rotations, 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. Many commercial vegetable types can become infected with the soilborne fungus S. rolfsii. Vegetable crops grown in regions that have predominantly warm, humid growing seasons are susceptible to this disease. The disease spreads most effectively between 25-30C. Significant economic losses have been attributed to southern blight in tomato, green beans, cantaloupe, peppers, and potatoes. Although difficult to assess, the economic losses caused by S. rolfsii can be quite severe due to the possibility of total destruction of the crop in some species. Estimates have been made that at least 5% of the annual loss of crops in the southern United States could be attributed to this disease-causing organism. Damage to solanaceous vegetable crops seems to average between 25-30% of the total number of plants in the field. The well-documented deleterious environmental effect of the unmitigated use of pesticides is an important reason why fruit and vegetables growers should be looking towards integrated pest management as an alternative. Treatments such as composting, biofumigation, and solarization will act to establish and maintain a disease suppressive soil microecology. Such an environment will resist the introduction and proliferation of soilborne pathogens and reduce pesticide requirements.

Collaborators:

Martin Lyons

mlyons@utk.edu
Graduate Research Assistant
University of Tennessee
369 Ellington Plant Science Bldg.
Knoxville, TN 37907
Office Phone: 8659748820