Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 3/17/2009
Publication Date: 8/1/2009
Citation: Gigot, J., Zasada, I.A., Walters, T. 2009. Occurrence of Phytophthora rubi and Pratylenchus penetrans in northwestern Washington red raspberry Fields. Phytopathology. 99:S43. Interpretive Summary:
Technical Abstract: The Pacific Northwest of the United States encompasses 90% of processed raspberry acreage nationwide. The duration of harvestable plantings has declined from >10 to approximately 5 yrs. Root damage by Phytophthora rubi (Pr) and Pratylenchus penetrans (Pp) has been associated with this decline, but soil characteristics that promote these pathogens are not well understood. Ten fields with root rot symptoms were sampled (10 sites per field; 10 soil cores (15 cm deep) per site) within Skagit and Whatcom Counties in October 2008. Soil samples were sieved (2 mm diam.) and root fragments were collected. Root sections (1 cm) were surface-sterilized and cultured on P5ARP agar medium to recover Pr. A subsample of root sections was also evaluated by ELISA (10 sites/ field) and PCR (3 sites/field) for presence of Phytophthora spp. and Pr, respectively. Population densities of Pp were determined from root and soil samples. A composite soil sample from each field was sent to a commercial laboratory for chemical analysis. All fields had sites that were positive for Phytophthora spp. (30-100% of sites per field) and seven fields were found to have excessively high (>1,000 g/root) levels of Pp. Sampled fields had a wide range in pH (4.2 to 6.8), organic matter (3.3-8.7%) and available nitrate (2-145 ppm). Further analyses are in process to understand the contribution of these pathogens to raspberry root rot and decline.