The ginseng root pathogens Cylindrocarpon destructans and Phytophthora cactorum are not pathogenic to the medicinal herbs Hydrastis canadensis and Actaea racemosa

Abstract

Goldenseal (Hydrastis canadensis) and black cohosh (Actaea racemosa, syn. Cimicifuga racemosa) are medicinal herbs that are indigenous to North America. Both are potential companion or rotation crops in shadecultivated ginseng (Panax quinquefolius) production systems. The susceptibility of H. canadensis and A. racemosa to three serious root diseases of P. quinquefolius was determined in a series of inoculation trials. Plants of the three species were grown in a shaded greenhouse and inoculated with isolates of Phytophthora cactorum, Cylindrocarpon destructans, or Rhizoctonia solani known to be virulent to ginseng. Panax quinquefolius plants were severely diseased or killed by the pathogens. However, P. cactorum and C. destructans were not pathogenic on H. canadensis or A. racemosa. Rhizoctonia solani caused damping-off of emerging seedlings of all three species.