Verifying critical control points for Phytophthora introduction into nurseries

Abstract

The Oregon Department of Agriculture implemented the Grower Assisted Inspection Program (GAIP) for nurseries in 2007. Participants in GAIP adopted best management practices (BMP) for five critical control points (CCP) (used containers, irrigation water, soil substrate, potting media, and incoming plants), where foliar Phytophthora can be introduced into nurseries. The goal of this study was to determine the presence or absence of Phytophthora at four CCP in GAIP nurseries 3- to 4-years after implementation of the program. From January to March 2011, samples were collected from irrigation water, potting media, used containers, and soil substrate at 13 GAIP nurseries. Irrigation water samples were collected from each nursery's water source. Potting media samples were collected from individual media components and from finished media. Potting media and debris were scraped from the insides of 25 used containers to create a composite used container sample per nursery. Transects were walked within each nursery, with inspectors collecting soil subsamples at three points located equidistant along each transect to create one composite soil substrate sample per transect. All samples were tested by baiting with healthy Viburnum davidii Franch. leaves followed by plating on PARP. A total of 354 samples were collected from all CCP checked in this study, with 30.2 percent testing Phytophthora positive. Phytophthora was detected in 10.3 percent, 30.4 percent, 36.4 percent, and 45.5 percent of potting media, used container, soil substrate, and irrigation water samples, respectively. Phytophthora incidence in irrigation water and soil substrate samples was significantly different from the incidence in potting media samples (p < 0.05), although there was no significant difference between soil substrate and used container samples. when looking at the number of nurseries with Phytophthora detected at each CCP, soil substrate (92.3 percent of nurseries) and irrigation water (66.7 percent of nurseries) were significantly more likely to be sources of potential contamination than potting media (30.8 percent of nurseries) and used containers (33.3 percent of nurseries) (p < 0.05).

Parent Publication

• Proceedings of the sudden oak death fifth science symposium

Citation

Osterbauer, N.K.; Lujan, M.; McAninch, G.; Trippe, A.; Lane, S. 2013. Verifying critical control points for Phytophthora introduction into nurseries. In: Frankel, S.J.; Kliejunas, J.T.; Palmieri, K.M.; Alexander, J.M. tech. coords. Proceedings of the sudden oak death fifth science symposium. Gen. Tech. Rep. PSW-GTR-243. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 149-153.