Other than the continued damage as a result of frost, the ginseng crop is proceeding as normal at this time, if there is such as thing as normal in ginseng. The typical root disease issues are beginning to show up including Cylindrocarpon, Pythium and Phytophthora. Hot and calm conditions over the last few days may have caused some heat stress in poorly ventilated gardens. Heat stress symptoms can include senescence of the leaf edges and papery sections of the leaves.
Growers should be monitoring the crop closely for moisture stress. This is best done with a soil moisture probe. Optimal soil moisture is especially important for seed production. Hot and dry conditions can lead to seed abortion or poorly developed seeds that are more prone to infection by fungi in the field or after harvest. Click here for more information on soil moisture monitoring for ginseng.
Growers are preparing land to be seeded in August. It is very important to keep these fields weed free until the crop is planted. Any soil pathogens or nematodes that survived fumigation can live and multiply on weedy hosts until seeding and can then live on cereals until ginseng germinates next spring. In addition, insects can use weedy hosts for egg laying and these may affect ginseng the following year. This is potentially a way that white grubs (European chafer) can affect the ginseng crop despite fumigation. Weed development in a ginseng garden during this time is a good indication of poor fumigation practices.
The ginseng replant research projects are progressing well. Figure 1 shows the tarp trial is being established this year. This trial is looking at the efficacy of solarization and anaerobic soil disinfestation. This is one of 4 new research trials established in 2015.