Control of Soilborne Plant Pathogens of tomatoes with incorporation of Indian Mustard (Brassica juncea)

Control of Soilborne Plant Pathogens of tomatoes with incorporation of Indian Mustard (Brassica juncea)

Summary

We investigated the potential of Brassica species as a biofumigation cover crop for control of soilborne disease in tomato production. In a laboratory jar test, Indian mustard inhibited mycelial growth of Sclerotium rolfsii, the fungal agent that causes Southern blight of tomatoes. In field trial, Brassica cover crops (B. juncea L and B. campestris) grew over winter and were tilled into the soil the following spring. In Spring 2000, marketable tomato fruit yield was significantly higher in the Brassica treated plots than in the control plots treated with rye. In Summer 2001, marketable tomato fruit yield was not significantly different between treatments.

Objectives/Performance Targets

The overall objective of this study is to determine the feasibility of Brassica sp. green manures as a natural alternative to methyl bromide. Pursuant with this goal, many factors were investigated. This study looked at the ability of mustard-biofumigation to control individual soilborne pathogens and the relationship of isothiocyanate production and pathogen control. The field study investigated implementation of biofumigation in field settings and looked at its integration with sustainable agricultural systems. Additionally, isolation of individual glucosinolates and determination of the lethality of each specific isothiocyanate was completed to aid in screening Brassica sp. for field use.

Accomplishments/Milestones

Harvey, Stephanie G., Heather N. Hannahan and Carl E. Sams. 2002. Indian mustard and allyl isothiocyanate inhibit Sclerotium rolfsii. J. Amer. Hort. Sci. (In Print).

Harvey, Stephanie G. and Carl E. Sams. 2001. Biofumigation Utilizing Brassica sp. Increases Marketable. HortScience Vol. 36(3). (Abstract).

Harvey, Stephanie G. and Carl E. Sams. 2001. Brassica biofumigation increases marketable tomato yield. Proc. Methyl Bromide Alternatives Conference.

Biofumigation Utilizing Brassica sp. Increases Marketable Tomato Yield. ASHS 98th Annual Conf. & Expo. June 2001. (Oral)

Allyl isothiocyanates released from Brassica juncea suppresses Sclerotium rolfsii. Proc. MeBr Alte. Conference. January 2001. (Poster)

Impacts and Contributions/Outcomes

With the ban of methyl bromide approaching, growers need an alternative control method for soilborne pathogens. While other chemical methods of control are currently available, their continued availability may be questioned. Increased interest in non-chemical methods for pest control furthers the need for alternative research.

In 2000, under high disease pressure, biofumigation did increase tomato yield over incorporation of a conventional winter cover of rye. Due to a later planting, the 2001 crop was subjected to less disease pressure and no signifcant differences were detected. Biofumigation with Indian mustard and other Brassica sp. may provide growers with an affordable, environmentally safe alternative to replace methyl bromide.

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