Detection of Aphanomyces euteiches in Field Soil from Northern Idaho by a Wet-Sieving/Baiting Technique

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Abstract
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.