Efficacy of fumigants and biofumigants for the control of replant disease of American ginseng (Panax quinquefolius)

Abstract

Abstract Ginseng replant disease (GRD) prevents the successful production of a second ginseng crop on the same ground even decades after the first crop. A study was initiated in 2013 to compare the efficacy of fumigants and biofumigants at two sites: (1) a replant garden planted to ginseng one year after a crop had been harvested, and (2) a non-replant site in which ginseng had never been grown. Treatments included chloropicrin and metam-sodium fumigants covered in totally impermeable film (TIF), un-tarped metam-sodium, modified mustard seed meal (MSM), and a mustard-capsaicin product (MC), and both a tarped and un-tarped control. Treatments were applied in June and July 2013 and ginseng seeded in August 2013. Plant stand was assessed monthly throughout the trial beginning after germination in spring 2014, and yield and quality were assessed at harvest in 2016 (replant site) and 2017 (non-replant site). At the replant site, plant stand declined rapidly in the un-tarped control, MSM, and MC treatments in the seedling year with no roots surviving to harvest. Although all plots had some disease at harvest, chloropicrin, metam-sodium, and the tarped control significantly improved yield. Disease pressures were low at the non-replant site and there were no consistent differences among treatments. Using Koch’s postulates, the cause of the rot in the replanted plot was confirmed to be Ilyonectria mors-panacis, although other factors are likely involved in the disease. Plant parasitic nematodes were not present in the replant site suggesting they may not be important factors in replant disease severity.