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 Phytophthora 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 growth of these pathogens and reducing survivability of these pathogens by using short-cycle mustard cover-crops is the goal of this study.

Experiments were conducted in 2010 in a P. capsici-infested field with a history of Phytophthora blight. Seeds were sown on 26 April and mustard plants were collected on 1 July (65 days after sowing seeds). Both FBL and Tilney mustard plants were at full-bloom, when mustard plants were collected. The plants 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.

Mean number of oospores in one gram of soil prior to incorporation of mustards were 1.83, 1, 1 and 1.92 in the plots used for FBL, Tilney, FBL+Tilney, and control treatments, respectively. Mean number of oospores in one gram of soil after incorporation of mustard were 1.5, 1, 0.42, and 1.5 in FBL, Tilney, FBL+Tilney, and control plots, respectively. Mean number of oospores after incorporation of FBL + Tilney was significantly lower than that of the same plot area prior to incorporation of mustard plants.

There was no vine infection in “Eureka’ cucumber. The rates of infected vines of ‘Magic Lantern’ and ‘Dickinson’ pumpkin combined were 19.11, 25.91, 22.96, and 19.33% in FBL, Tilney, FBL+Tilney, and control treatments, respectively. Overall rate of fruit infection in ‘Eureka’ cucumber, ‘Magic Lantern’ pumpkin, and ‘Dickinson’ pumpkin were 25.74, 23.77, and 20.32%, respectively, which were not significantly different from each other. No Fusarium infection on any fruit was observed.

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. The results of field trials have not been consistent. Although mustard cover crops affected growth and survival of P. capsici, cover crop alone may not be sufficient to protect cucurbit crops against P. capsici. However, integration of mustard cover crops with crop rotation and fungicide use could provide sustainable protection of cucurbit crops against P. capsici and Fusarium spp. More research studies in this regard are needed.

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