Distinguishing Aphanomyces Root Rot from Rhizoctonia Root and Crown Rot Rhizoctonia root and crown rot is another soilborne fungal disease common in western Nebraska. It is caused by a different pathogen, Rhizoctonia solani, but may be confused with Aphanomyces root rot. Rhizoctonia is similar to Aphanomyces root rot in that it is more severe in warm, poorly drained soils. However, symptoms can be easily distinguished between the two diseases. No yellowing is observed as is with the chronic phase caused by Aphanomyces.
Infection also can occur on roots after cultivation if soil is thrown into the crowns.
This ability to distinguish between the two diseases is particularly important now because fungicides are being developed with new chemistries effective for controlling Rhizoctonia root and crown rot. Plant early into cool soils to more quickly establish a crop before the pathogen becomes active as soils begin to warm. Plant cultivars with some tolerance to the pathogen. There are no locally adapted cultivars with specific resistance to A. cochlioides, but several cultivars that appear to have some field tolerance, and still can yield well in the presence of the pathogen. Do not evaluate plants for moisture stress in the afternoon, when both infected and healthy plants can wilt.