Management strategies for Alternaria leaf blight on American ginseng

Cultivated American ginseng (Panax quinquifolius) is a perennial herb valued as traditional Chinese medicine. The crop commercially produced under polypropylene shade cloth, creating climate favorable for leaf blight caused by Alternaria panax; frequent fungicide applications are required annually to protect yields of the root and seed. Our objective was improve tactic identifying effective products application intervals using calendar or TOM-CAST disease forecaster. Product efficacy trials were conducted at two sites over years included 14 an untreated control. fungicides pyraclostrobin azoxystrobin + difenoconazole consistently in limiting compared Fluxapyroxad also both across with one exception. Mancozeb, fluazinam, chlorothalonil, difenoconazole, penthiopyrad when pressure not severe. Applications mancozeb resulted higher seedhead yield than forecaster, spray thresholds 10 15 severity values (DSVs) tested four field each applied every 7 days (untreated control). All treatments three limited control years. According area progress curve (AUDPC) data, treatment programs 2013 similar better AUDPC data from 2014 indicated that 7-day had fewer diseased plants all sites; DSV sites. yielded similarly 10-day site fresh dried root; similar. At second site, treatments; may provide balance between reducing while protecting valuable yields.