Biorational approaches for management of bacterial wilt and bacterial spot on tomato

Biorational approaches for management of bacterial wilt and bacterial spot on tomato

Summary

The purpose of this project is to develop environmentally compatible approaches for management of bacterial wilt and bacterial spot of tomatoes. We hired a postdoctoral research associate on June 1, 2006. Some of the greenhouse house and field experiments planned under objectives 1 and 2 were conducted.

Objectives/Performance Targets

Objectives:
1. To develop strategies in integrated management of bacterial wilt:

a. Evaluate the efficacy and application methods of new biofumigants and reduced risk compounds in control of R. solanacearum on tomato under greenhouse and field conditions.

b. Evaluate integrated effectiveness and economics of field application of Actigard, biofumigant (thymol), and commercial tolerant or resistant tomato genotype (FL 7514, BHN 669) in the management of bacterial wilt.

2. To optimize integrated management of bacterial spot with the SAR inducer Actigard, PGPRs and bacteriophages.

a. Determine if lower rates of Actigard can be applied to enhance disease control without affecting tomato yield and identify resistant lines to determine if they respond to PGPRs.

Accomplishments/Milestones

1. a. The effectiveness of carvacrol, geraniol, linalool, yucca extract, phosphorous acid, and Serenade was evaluated in greenhouse experiments against bacterial wilt of tomato. Carvacrol, geraniol, and linalool were effective as thymol. Yucca extract and Phosphorous acid were significantly better than untreated control. Serenade with Phyton 27 did not reduce the disease incidence.

1. b. The combined effects of thymol and Acibenzolar-S-methyl (Actigard 50WG) are being evaluated in a field experiment in the fall of 2006. Commercially available moderately resistant tomato cultivars (FL 7514 and BHN 669) are included in the experiment and a susceptible cultivar Phoenix is used as a control. Thymol was applied through drip irrigation lines and ASM was used for foliar spray and soil drench as described above. This field experiment is a randomized complete block design with a split plot arrangement for the cultivars. Thymol provided consistent protection against bacterial wilt on all the tomato cultivars. And integrated use of thymol, ASM, and the two moderately resistant cultivars provided the greatest disease reduction among the treatments.

2.a. In this study, the integrated efficacy of reduced rates of Actigard and host resistance for managing bacterial spot of tomato was evaluated in two greenhouse experiments. All rates of Actigard significantly reduced disease severity compared with untreated control on both susceptible and resistant genotypes. Efficacy of different rates of Actigard on resistant genotypes was similar. On susceptible genotypes, Actigard’s efficacy was significantly different based on application rates. Integration of these tactics needs to be further evaluated in field experiments. Other greenhouse experiments for bacterial spot did not work well due to temperature problems.

Impacts and Contributions/Outcomes

Integrated use of thymol (or a Label product with similar efficacy), Actigard, and the two moderately resistant cultivars provided the greatest disease reduction among the treatments. This will be a promising tactic to try in a demonstration trial in 2008. Actigard 50WG is a plant activator that induces systematic acquired resistance (SAR) in tomato for a number of diseases including bacterial spot caused by Xanthomonas perforans. Deployment of resistant cultivars to bacterial diseases coupled with the use of SAR inducers may increase durability of host resistance and enhance disease management program.

Collaborators: