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ARS Home » Southeast Area » Poplarville, Mississippi » Southern Horticultural Research Unit » Research » Publications at this Location » Publication #312139
Title: Phytophthora species recovered from irrigation reservoirs in Mississippi and Alabama nurseries and pathogenicity of three new species.

Author
item Copes, Warren
item YANG, XIAO - Virginia Polytechnic Institution & State University
item HONG, CHUANXUE - Virginia Polytechnic Institution & State University

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/26/2015
Publication Date: 10/1/2015
Citation: Copes, W.E., Yang, X., and Hong, C.X. Phytophthora species recovered from irrigation reservoirs in Mississippi and Alabama nurseries and pathogenicity of three new species. Plant Disease 99:1390-1395.

Interpretive Summary: Nursery containment ponds that capture irrigation run-off and are a source of irrigation water were surveyed for Phytophthora species that are plant pathogens causing crop loss. Nine Phytophthora spp. were recovered from containment ponds, and several were common to all ponds sampled. Some species were collected just in warmer or cooler times of the year. Three of the nine were new Phytophthora species and have now been named and described. Trials were performed to test their potential to cause plant disease on annual vinca, gardenia, pieris, oakleaf hydrangea, holly, and rhododendron. The three species did not cause disease or survive in the organic substrate in the container. The nine Phytophthora spp. recovered from containment ponds appear to present a low risk to the ornamental plants at nurseries. This adds to the growing information that indicates many aquatic Phytophthora species are not causing significant economical crop loss. This information will be useful to growers, extension specialists, and crop advisors.

Technical Abstract: From a survey of containment ponds for Phytophthora spp. at one nursery each in Alabama and Mississippi, eight species and one taxon were recovered with P. gonapodyides dominant in cooler months and P. hydropathica in warmer months, accounting for 39.6% and 46.6% overall recovery, respectively. Among the recoveries were P. macilentosa, P. mississippiae and P. stricta, three new species recently described from a small lake (labeled as M4) that serves as a primary water source to feed the irrigation pond (M5) at the Mississippian nursery. Neither of ponds M4 and M5 directly receive runoff from any production area. These three species were tested for pathogenicity with Catharanthus roseus, Gardenia jasminoides ‘August Beauty’, Hydrangea quercifolia ‘Semmes Beauty’, Ilex magland ‘Oakland’, Pieris japonica 'Mountain Snow', and Rhododendron × 'Brandi Michele Raley'. None of the three species infected any of the test plants or became established in the peat or pine bark growing media. Based on the result of pathogenicity trials as well as the observation that none of the Phytophthora species recovered from irrigation reservoirs have caused disease in the nurseries, the eight Phytophthora spp. and one taxon appear to present a low risk to the ornamental plants at those nurseries.