Evaluation of Compost Tea Application to Control Foliar Diseases in an Heirloom Tomato Crop

Project Overview

Project Type: Farmer/Rancher
Funds awarded in 2006: $9,720.00
Projected End Date: 12/31/2008
Region: Southern
State: Georgia
Principal Investigator:
Daniel Parson
Gaia Gardens


  • Vegetables: tomatoes


  • Crop Production: application rate management
  • Pest Management: field monitoring/scouting

    Proposal summary:

    Heirloom tomatoes are an important cash crop for organic farmers. However, the susceptibility of tomato varieties to foliar diseases such as early blight (Alternaria solani), leaf spot (Septoria lycopersici), and bacterial spot (Xanthomonas campestris) limits their season in the humid climate of northern Georgia. Identifying effective natural treatments that can delay the onset of foliar diseases would extend the heirloom tomato season, and ultimately make growing heirloom tomato varieties more profitable for organic growers. The goal of our project is to test the efficacy of aerated compost teas as treatments to delay onset of foliar diseases in and increase yield of heirloom tomato crops. Compost teas have been shown to help control a variety of foliar diseases on horticultural crops. We are aware of several recent studies that examined the capability of compost teas to suppress diseases of tomatoes. However, these studies focused on hybrid tomato crops grown in research plots. We are interested in testing heirloom varieties grown under production conditions. Our specific aims are to: 1) make and determine the microbial community structure of two compost tea formulations, 2) determine the reproducibility of the microbial communities extracted in the two compost tea formulations, and 3) determine the efficacy of each formulation of compost tea by comparing a) presence and degree of foliar disease, b) fruit yield, and c) length of season in tomato plants treated with each compost tea formulation to tomato plants treated with water over the course of the growing season. We will use four replicate plots of 16 Cherokee purple tomato plants to test our three treatments. The experimental design will be a randomized complete block design (RCBD). Starting at the time of transplant, five plants in each replicate plot will be sprayed with water each week as a negative control, five plants will be sprayed with KISCT, and five plants will be sprayed with 5SCT. All plants will be sprayed on the same day of each week. Microbial analysis of the compost tea and leaf samples will be performed one time per month. A sample of each formulation of compost tea will be taken and analyzed for total and active bacteria, and total and active fungi. Leaf coverage will be assessed by taking leaf samples before compost tea application and 20—30 minutes after application from the top, middle and bottom of the inside and outside of five plants from each treatment. Each week, the plants will be examined to determine: 1) presence of fungal and bacterial foliar disease, 2) percentage of leaf surface exhibiting foliar disease, 3) fruit yield (weight of diseased and non-diseased fruit), and 4) plant death. The efficacy of the compost tea formulations will be determined using a RCBD analysis of variance model. The variables tested using the model will include: 1) number of days of delay of onset of any fungal or bacterial foliar disease normalized to the water-only control, 2) weekly ratio of leaf surface exhibiting disease normalized to the water-only control, 3) weekly and total seasonal yield, and 4) weekly ratio of viable plants receiving each treatment. The relation between the microbial biomass, activity and community structure in the compost tea and on the plant leaves (independent variables) and foliar disease (dependent variable) will be assessed using univariate and, if appropriate, multivariate analysis.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.