Importance of Brassica soil amendments for managing soilborne disease in ornamentals and vegetables

Importance of Brassica soil amendments for managing soilborne disease in ornamentals and vegetables

Summary

Soilborne pathogens of ornamental and vegetable crops cause production losses every year. The purpose of this project is to determine the appropriate cultivars and application rates of Brassica crops for management of nematodes and Rhizoctonia solani on vegetable and ornamental crops when incorporated as a biofumigant. The root-knot nematode and the fungus R. solani were selected for assessment because of the significance of these pathogens in vegetable and ornamental production. Micro-plot studies were initiated in 2007 to examine the value of canola and Indian mustard, including one Indian mustard selected for high glucosinolate production, at three rates of application. From the first year of tests, it appears that rate of application of Brassica biomass is more influential than cultivar selection for disease management of R. solani and M. incognita. The canola cultivar selected was B. napus cv. Jetton, and the mustard cultivars were Bionute and Fumus. Another set of studies is examining the duration of suppressive effects of Brassica soil amendments on a range of pathogens. This research will help clarify the efficacy of Brassica green manures for the control of soilborne pathogens. In addition, the importance of cultivar selection or Brassica species and rate of application should be demonstrated. The research should assist in making recommendations for the timing of Brassica amendments in relation to planting or transplanting operations for protection against existing and introduced soilborne pathogens.

Objectives/Performance Targets

The objectives of this study are

1. To determine the importance of Brassica cover crop selection and biomass application rates in relation to disease management of the root-knot nematode, Meloidogyne incognita, affecting cucumber.

2. To determine the importance of Brassica cover crop selection and biomass application rates in the disease management of Rhizoctonia solani AG-4 on petunias and impatiens.

Accomplishments/Milestones

The purpose of this project is to determine appropriate cultivar selection and application rate of Brassica crops for management of nematodes and Rhizoctonia solani on vegetable and ornamental crops. Brassica tissues have been reported to have beneficial effects in the management of soilborne diseases when used as a biofumigant. Brassicas contain secondary metabolites, such as glucosinolates, which decompose into biocidal chemicals, which are thought to manage pathogen populations including fungi and nematodes. While previous projects have attempted to assess the effectiveness of Brassica soil amendments, few studies have examined the effectiveness of different Brassica crops or cultivars within a species. In addition, the need or benefit of selecting a cultivar high in glucosinolates and rate of biomass application have not be defined. The objectives of this study are 1) to determine the importance of Brassica cover crop selection and biomass application rates on disease management of the root-knot nematode, Meloidogyne incognita, on cucumber and 2) to determine the importance of Brassica cover crop selection and biomass application rates in the disease management of Rhizoctonia solani AG-4 on petunias and impatiens. The root-knot nematode and the fungus R. solani were selected for assessment because of the significance of these pathogens on numerous vegetable and ornamental crops for a range of production operations, including limited resource farmers and organic producers. Micro-plot studies were initiated in 2007 and will be repeated in 2008 to examine the value of canola and Indian mustard, including an Indian mustard cultivar bred for high glucosinolate levels, at three rates of application. The canola cultivar selected was B. napus cv. Jetton, and the mustard cultivars were Bionute and Fumus. From the first year of evaluations, it appears that rate of application of Brassica biomass is more important than cultivar or species selected for disease management of R. solani and M. incognita. Another set of studies is examining the duration of suppressive effects of Brassica soil amendments on a range of pathogens.

Impacts and Contributions/Outcomes

This research will help clarify the efficacy of Brassica green manures for the control of soilborne pathogens. In addition, the importance of cultivar selection or Brassica species and rate of application should be demonstrated. The research should assist in making recommendations for the timing of Brassica amendments in relation to planting or transplanting operations for protection against existing and introduced soilborne pathogens.

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