Determining the effectiveness of mustard short-cycle cover crops in managing soil-borne fungal pathogens in cucurbits

Determining the effectiveness of mustard short-cycle cover crops in managing soil-borne fungal pathogens in cucurbits

Summary

This study was conducted to determine the effectiveness of two mustard species, Brassica alba, ‘Tilney’ (T), and Brassica juncea, ‘Florida Broadleaf’ (FB), as short-cycle cover crops, for managing Phytophthora blight (Phytophthora capsici) of cucurbits.

Objectives/Performance Targets

This proposal is a two-year project to determine the effectiveness of mustard short-cycle cover crops in managing soil-borne P. capsici and Fusarium spp in cucurbit fields. The specific objectives are: (i) to compare the effects of the planting seasons of mustard on glucosinolate profile and their release in to the soil; (ii) to determine the specific glucosinolates and their concentration in leaves, root and stem; and (iii) to determine the relationship between allelochemical composition, concentration and pest suppression of the chemicals with fungicidal activities for developing biocontrol integrated pest management (IPM) strategies.

Accomplishments/Milestones

Phytophthora blight of cucurbits, caused by Phytophthora capsici, is the most destructive disease of cucurbits. There is no single method available to provide adequate control of this disease. Also Fusarium spp. cause plant infection and considerable fruit rot in all cucurbits. All of these pathogens are soil-borne fungi. Suppressing survival and growth of these pathogen by using short-cycle mustard cover-crops is the goal of this study.

Experiments were conducted during 2008-2009 in a P. capsici-infested field with a history of Phytophthora blight. Mustards were grown in the field for 45 days and were incorporated into the top 10-cm layer of the soil. The seeds of cucumber (‘Eureka’), jack-o-lantern pumpkin (‘Magic Lantern’), and processing pumpkin (‘Dickinson’) were sown after the incorporation of mustard into the soil. Average density of P. capsici oospores per gram of dry soil was 2.67 prior to incorporation of mustard plants. The density of oospores was 1, 1.66, 2.33, and 0 in control, T, FB, and T+FB plots, respectively, 14 days after the incorporation of mustard plants into the soil. There was no vine infection in cucumber plots. Incidence of vine infection on jack-o-lantern pumpkin plots was 52.92, 43.13, 32.70, and 51.04 %; and on processing pumpkin the incidence was 45.00, 52.71, 48.33, and 47.29 % in control, T, FB, and T+FB plots, respectively. Incidence of Phytophthora fruit rot on cucumber was 26.91, 20.83, 12.93 and 13.44 %; on jack-o-lantern pumpkin, it was 24.43, 31.63, 22.75, and 28.80 %; and on processing pumpkin, the incidence was 26.20, 18.80, 22.69, and 45.37 % in the control, T, FB, and T+FB plots, respectively.

There was not a significant occurrence of Fusarium diseases in the experimental field in either 2008 or 2009. Incidence of Phytophthora blight was reduced in the mustard-treated plots. Thus, it appears that short cycle cover crop is going be a component of an integrated approach for management of Phytophthora foliar blight and fruit rot of cucurbits.

Impacts and Contributions/Outcomes

Short term outcome of this project is to determine the effectiveness of short cycle mustards in reducing the incidence and severity of diseases caused by Phytophthora capsici and Fusarium spp. in cucurbit fields. The intermediate- and long-term objectives of this study are to develop effective IPM strategies for management of soil-borne pathogens in vegetable fields by using cover crops. We are still investigating the significance of using short cycle mustards for management of diseases caused by Phytophthora capsici and Fusarium spp. in the fields. The outcomes are not definite yet, as we are experiencing inconsistent results. We, however, are optimistic that using short cycle mustards, either alone, or in combination with other methods (e.g., crop rotation and using fungicides) can be used to effectively manage diseases caused by Phytophthora and Fusarium spp.

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