Control of Soilborne Fungi with Biofumigation

View the project final report

• 2004 annual report
• 2005 annual report

Commodities

• Vegetables: tomatoes

Practices

• Crop Production: organic fertilizers, tissue analysis
• Farm Business Management: budgets/cost and returns
• Production Systems: general crop production
• Soil Management: composting, earthworms, nutrient mineralization

Alternative methods to control soilborne pathogens are urgently needed. This is because 1) methyl bromide will be unavailable as a preplant soil fumigant in 2005, 2) there is increasing pathogen resistance to pesticides, and 3) pesticides adversely affect the environment. Biofumigation is the control of soilborne pests and pathogens when glucosinolates in Brassica species are hydrolyzed upon incorporation into the soil. Many biofumigation studies have been conducted in vitro, where isothiocyantes (one breakdown product of glucosinolate) have been shown to be fungitoxic and fungistatic, particularly to Fusarium. It is therefore important to evaluate biofumigation in the field for the control of Fusarium and other soilborne pathogens, plus monitor populations of beneficial organisms after biofumigation. Isothiocyantes are volatile compounds and increasing their residence time in soil might increase pathogen control. Results from biofumigation in combination with plastic mulch have implied increased soil residence time, but none of the researchers sampled soil to confirm this. The objectives of the study are to a) evaluate the effectiveness of biofumigation in the control of Fusarium wilt on a susceptible watermelon cultivar, compared to control with methyl bromide; b) determine the best time to incorporate green manure prior to laying plastic; c) quantify inoculum density of Fusarium oxysporum f. sp. niveum, Rhizoctonia solani, Pythium spp., Sclerotium rolfsii, and fluorescent Pseudomonas in the soil before and after biofumigation; d) determine glucosinolates concentration in roots and shoots of the brassicas at the time of incorporation; and e) quantify glucosinolate breakdown products in the soil after brassica incorporation.

The objectives of the biofumigation study are to
1)Evaluate the effectiveness of biofumigation in the control of Fusarium wilt of watermelon, compared to control with methyl bromide.
2)Determine the best time to incorporate green manure prior to laying plastic (i.e., let the biofumigant decompose before tarping, or tarping immediately after plowing under).
3)Quantify inoculum density of Fusarium oxysporum, Rhizoctonia solani, Pythium spp, Sclerotium rolfsii, and fluorescent Pseudomonas in the soil before and after biofumigation.
4)Determine glucosinolate concentration in roots and shoots of the brassicas at the time of incorporation.
5)Quantify glucosinolate breakdown products in the soil after brassica incorporation.