The ginseng crop has fully emerged and canopies are expanding. We have accumulated 300 GDD (Base 5) so far this year as of May 15. Normally we don’t reach that level until May 25. The only year in which we reached 300 GDD earlier in the last 25 years was 2012, when it was reached two days earlier. By the weekend, 2024 will pass 2012 as the warmest for temperatures and likely earliest for crop development in the last 25 years. While warm or even hot weather periods are relatively common in late April and early May, what is unprecedented this year is the early warmth, the duration of the warmth, and the abnormally warm night temperatures for this time of year.
This level of spring warmth will have an impact on some aspects of ginseng production:
1. The risk of frost is normally a concern with early emergence, but there is no risk of frost in the current 7-day forecast.
2. Any insect pests of ginseng are likely to emerge 10 days early this year. This includes slugs and cutworms which have already emerged, four lined plant bug, which is emerging now (although very localized in ginseng), and leaf folders which will start to emerge soon. It is best to time scouting activities and any management options for different pests based on the stage of crop development rather than the calendar. Diseases may develop early as well based on early canopy closure, but disease development also depends on specific rainfall and humidity conditions rather than strictly air temperatures.
3. Adding an extra 10 days of a full canopy at a time when daylengths are nearing their longest could increase root growth and yield for the year but is obviously dependent on the weather conditions for the rest of the summer.
Foliar Phytophthora
Foliar phytophthora has been found this past week in the area of a former phytophthora trial in the OGGA research garden which is entering its third year. This likely means there was an infection period about two weeks ago. If the main stem is infected the entire top may droop over resulting in the classic shepherds crook appearance (Figure 1). Sometimes just a single leaf is affected, which will droop straight down (Figure 2). At this time of year single lesions on leaves are rare because the leaves were not unfolded at the time of infection.
Figure 1. A ginseng top drooped over on May 15 as a result of foliar phytophthora on the main stem.
Figure 2. A single leaflet drooping straight down as a result of foliar phytophthora on the petiole (leaf stem) of a leaflet.
While the risk of further spread is relatively low based on a mostly dry forecast, any localized rains that keep foliage wet for extended periods could lead to further spread. Ensure protection of the crop from both foliar and root rot phases of the disease. The area of the symptoms has very little straw cover due to harvesting activities last summer, so is probably at higher risk for splashing of soilborne inoculum onto the leaves than typical commercial gardens.
Ginseng Scout Training
A reminder that ginseng scout training is scheduled for Thursday, June 6 (rain date June 7) from 1-3 pm at the OGGA research garden just north of 785 Byerlay Sideroad near Courtland. Registration is required so attendees can be updated on any potential changes to the schedule. Click here to register.
After registering using the link above, you will receive a confirmation email containing information about joining the meeting.
