Ginseng Crop Update – May 12, 2017

Temperatures will be finally warming up next week and become more humid as well. With frost damage in some gardens this will greatly increase the risk of Alternaria and Botrytis. If there is any frost damage in a garden, now is the time to protect those plants with a product that provides good protection from both diseases. A dual active product (e.g. Switch 62.5 WG) or a tank mix of compatible products are the best options. Consult the product companies to determine if two tank partners are compatible and follow the most restrictive restricted-entry intervals (REIs) and other label precautions of the two products you are mixing.

Growers will be preparing for fumigation over the month. Our research efforts over the past 6 years into fumigation practices have shown us some keys to successful fumigation.

  1. Ensure Good Soil Moisture. This point can’t be stressed enough. Without good soil moisture fumigation will not work well and you will be wasting your money. Even if you are applying chloropicrin with tarp, dry soils can result in rapid release of the fumigant into the air below the tarp and reduce efficacy. When the soil is dry, the fumigants tend to go straight up from the injection point, resulting in poor efficacy between the shanks. Low soil moisture also prevents a proper seal. Consult the label for the required soil moisture levels. Generally, 50-80% of field capacity is necessary depending on the fumigant. Field capacity is the amount of water the soil can hold after free water has drained away. Soil should not be fully saturated either or the fumigant will not move in the soil and it may be trapped there. It is illegal to apply a fumigant at a lower or higher soil moisture level than is indicated on the label.
  2. Seal the Soil Properly. Tarping provides the best seal of the soil surface because it prevents rapid escape of the fumigant and ensures the top layer of the soil is treated. This applies to all fumigants. If tarping is not possible, then adequate soil moisture will allow for a good seal of the soil surface if the fumigant is sealed with a roller. After rolling, an additional light irrigation will improve the seal if tarps are not being used.
  3. Prepare the Soil Ahead of Time. Any crop debris in the soil will reduce the efficacy of fumigation. Corn stubble or other large debris can break the seal of the soil surface and allow a chimney that will vent the fumigant much more rapidly. Fumigants also do not penetrate easily into large clumps of organic matter and pathogenic organisms can be protected in these clumps. After fumigation when most of the soil is sterilized, these pathogens can quickly re-colonize the soil since they will have minimal competition with other organisms.

Do not let a custom applicator’s schedule rush you into doing things improperly. There is plenty of time for fumigation over the next 2 to 3 months. The custom applicator cannot apply the fumigant under improper conditions anyway. Also ensure you follow all of the label requirements including fumigant management plans, signage and safety.

About Sean Westerveld

Ginseng and Medicinal Herbs Specialist, OMAFRA
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