Cover Crops for Use in Reducing Phytophthora Blight Damage to Bell Pepper (Capsicum Annuum)

Cover crops are plants grown to maintain and improve soil quality, reduce inputs to production systems and increase productivity. One particular benefit of growing cover crops is reduced infection of crop plants by soil-borne pathogens. Phytophthora blight is caused by the soil-borne oomycete Phytophthora capsici; a pathogen for many commercially grown vegetables within the Solanaceae and Cucurbitaceae families, and some members of the Leguminosae family. Infection occurs when there is excess soil moisture with warm, wet weather and affects plant roots, stems, foliage and fruit; with the latter two being infected when soil splashes onto plants by rain or overhead irrigation, transferring infectious zoospores. Soil between plastic-mulched beds, as are used for fresh-market bell pepper (Capsicum annuum L.) production, is normally kept weed-free. This bare ground, often compacted, with poor drainage, can serve as a source for Phytophthora blight infection. Our hypothesis is that a dead or living organic mulch, from cover crops in the inter row alleys, will reduce the incidence of Phytophthora blight in row crops. From initial observations during the first growing season, we saw that having a cover crop growing either side of the bed reduced the number of Phytophthora-damaged pepper fruits, in comparison to both bare soil and straw mulch, and had limited impact on pepper yield. Mowing the cover crop reduced the number of Phytophthora-infected peppers and increased cover crop biomass yield, compared to not mowing. Of the cover crops grown, Annual ryegrass (Lolium multiflorum Lam.) established quicker, yielded the greatest biomass, had the highest percentage groundcover and the lowest incidence of Phytophthora blight-infected pepper fruits, compared to Dutch white clover (Trifolium repens L.) and Creeping red fescue (Festuca rubra L. ssp. arenaria (Osbeck) F. Aresch.).

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