Detection of Aphanomyces euteiches in Field Soil from Northern Idaho by a Wet-Sieving/Baiting Technique. John M. Kraft, Supervisory Research Plant Pathologist, Vegetable and Forage Crops Production, Agricultural Research Service, U.S. Department of Agriculture, Prosser, WA 99350-9687. Joanna Marcinkowska, and Fred J. Muehlbauer. Plant Pathologist, Department of Plant Pathology, Warsaw Agricultural University, Warsaw, Poland 02-766; and Research Geneticist, Agricultural Research Service, U.S. Department of Agriculture, Pullman, WA 99164. Plant Dis. 74:716-718. Accepted for publication 28 February 1990. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1990. DOI: 10.1094/PD-74-0716.

Aphanomyces euteiches was detected at three locations in northern Idaho by a wet-sieving technique. Five-day-old pea seedlings were used to bait the fungus from the sieved organic fraction from 10 soil samples per field. Inoculated seedlings in rolled germination paper were incubated and observed at weekly intervals for 3 wk. Almost all fields sampled in the Grangeville area were severely infested, and fields in the Kendrick area and two out of six fields in the Genesee area were heavily infested with A. euteiches. This wet-sieving technique gave results similar to the greenhouse-pot technique currently used to determine Aphanomyces root rot potential and required no greenhouse space or special watering requirements. This technique revealed that infective oospores of A. euteiches were as deep as 60 cm in the soil profile and were present in areas with poor drainage in fields with low inoculum levels overall. A hierarchical statistical analysis was used to separate differences in inoculum levels within areas and between fields.