It is will be no surprise to ginseng growers that emergence of ginseng will be late this year, but how late will it be? We have had snow this late in the season before, and sometimes well into May, but often those are short lived bursts of cold. Looking through weather records at Delhi for the past 80 years, the last time it was this steadily cold this late in the season was in 1975. Depending on temperatures for the next few weeks, this will likely be the latest ginseng emergence that most growers have ever seen. It may be May 10 before older gardens start poking through the straw, unless we get a sudden heat wave in early May. The only unknown is how much the warmth in the end of February and the sunny weather through March may have moved things along in the soil.
So what does this mean for growers? First, there is no rush to get shades erected (unless it takes several weeks for you to get all of the shades put up). The chances for snow are low in the next week, so that may not be a big concern. However, snow can happen late and the longer you wait to put up the shades, the lower the risk. Second, in a normal year, growers are starting to think about the first fungicide applications of the season in the next week. Those can also be delayed this year, since applications at this time may have minimal effect in protecting the crop. Some fungicides like Ridomil and Orondis have upward mobility in the plant. These need to be taken up by the roots in order to protect the plant. If the plant is dormant and not taking up water, there will also be minimal uptake of the fungicide. These fungicides will still have some direct effects on pathogens in the soil, but will not protect the developing shoot as much as when the plant is actively developing.
Grower members of the OGGA received a copy of OMAFRA Publication 847 – Crop Protection Guide for Ginseng at the OGGA AGM in March. Growers not in attendance should receive a copy in the mail soon. This publication contains a list of all of the fungicides registered on ginseng up to November 2017, along with efficacy ratings for different diseases. Anyone else interested in the guide can purchase a copy for $5 plus tax from the OMAFRA Simcoe Resource Centre or online through Service Ontario.
Absent from publication are two fungicides that were registered after November 2017, Luna Sensation and Polyoxin D Zinc Salt 5SC. Luna Sensation (fluopyram + trifloxystrobin) is registered for control of Alternaria blight on Crop Group 1B including ginseng. It is a combination of a new active fluopyram and the active contained in Flint, which was already registered for use on ginseng for control of Alternaria. Research has shown good control of Alternaria on ginseng in field trials. Apply Luna Sensation at a rate of 300 to 500 mL/ha on a 7 to 14 day interval. Do not apply more than 1680 mL/ha in a single season. Luna Sensation must be rotated with non-Group 7 and 11 fungicides (e.g. do not rotate with Flint, Fontelis, or Sercadis). Trifloxystrobin, which is contained in both Flint and Luna Sensation, can only be applied a maximum of 4 times per season. Luna Sensation has a Restricted Entry Interval (REI) of 12 hours and a Pre-Harvest Interval (PHI) of 7 days.
Polyoxin D Zinc Salt 5SC is registered for control of Botrytis blight on ginseng. It is a Group 19 fungicide, which is a new group for ginseng, and good to use in fungicide rotations for resistance management. Research has shown fair to good control of Botrytis blight on ginseng. Apply Polyoxin D preventatively at a rate of 611 to 1222 mL/ha on a 7 day interval. Do not apply more than 3 times per season. Workers can re-enter treated fields once sprays have dried, and it has a PHI of 0 days, meaning it can be applied up to the day of harvest.
The information listed above is a brief summary of the product labels. Consult the labels for more details on use and precautions with these two products. As with all fungicides registered on ginseng, Maximum Residue Limits for these products will be different in importing countries. Care should be taken to avoid applications close to harvest, well beyond the listed PHI, to avoid residues on exported roots that are above the MRL of the importing country.