PHYTOPHTHORA OF CONIFERS – NEW AGENTS NOVEL APPROACHES AGAINST AN OLD ENEMY
Horticulture & Turfgrass
Timothy Waller
Agriculture & Natural Resources County Agent III
Rutgers
Millville
Abstract
Phytophthora spp. are omnipresent in horticulture production, however the focus of this USDA-SCBG was to reengage, map out the species affecting conifers and nurseries, and define better commercial recommendations in New Jersey and northeastern region. This endeavor allowed the new agents, onboarded at the onset of COVID-19, an opportunity to engage multiple commodities within a single program. Phytophthora is difficult to manage, and recommendations vary greatly across regions and commodities, yet innovative research in this area has not yet been exhausted. First, a short survey shared through county newsletters, the Rutgers Plant and Pest Advisory, and commodity association listservs, identified 21 grower cooperatives. During sampling visits the agents prepared a list of questions to unify verbal communication and delivered USDA - Web Soil Survey maps of their farms to direct discussions. Site, irrigation, host, and many other metrics were collected in addition to root and canker samples from symptomatic conifers and perennials. A total of 15 plant species, spanning the majority of Christmas tree and commonly infected nursery crops, were sampled. Samples were plated onto a Phytophthora selective media, PARPH, to obtain pure cultures. There appears to be 8-10 Phytophthora spp. contained within the 60+ isolates, however these groups will be sequenced at their ITS and COX2 genes for speciation. Morphological characterization and relation to host crops will aid in future diagnostics. Isolates were then subjected to a novel high-throughput 96-well bioassay to give indication of fungicide (conventional and biological) efficacy on the Phytophthora spp. groups, thus streamlining subsequent time-consuming field trials. Germplasm trials add the element of host susceptibility and thus allow experimental treatments focused on combinations of Phytophthora spp., treatments, and germplasm variables. Transplants were sourced from the major Christmas tree nursery regions of the USA for wide industry representation. This project is proving critical data and most importantly reengaging commodity groups. Outreach has taken the form of leading educational sessions for Christmas tree growers, commercial nurserymen, diversified farms, and landscape professionals (300+ overall attendees, at 3 sessions). Pest scouting guides, soil, site, and cultural deliverables are in progress as secondary results of this programming.
Authors: Timothy J. Waller, Ph.D. , Peter Oudemans , William Errickson, Devan Gladden
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Timothy J. Waller, Ph.D. Agriculture & Natural Resources County Agent III, Rutgers University, New Jersey, 08332
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Peter Oudemans Professor I, Rutgers University, New Jersey, 08019
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William Errickson Agriculture & Natural Resources County Agent III, Rutgers University, New Jersey, 07728
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Devan Gladden Undergraduate student intern - Plant Biology , Rutgers University - undergraduate , New Jersey, 08332