Ginseng Crop Update – July 15, 2016

Cutworms have been reported causing damage to mostly seedlings across the ginseng production area (Figure 1). The cutworms are still relatively small, so it will be important to control them before they cause more extensive damage. Proper timing and application procedures are very important for getting optimal control of cutworms.

160715 Figure 1
Figure 1. Cutworms coil up into a ‘C’ when disturbed and have a greasy skin. There are several species that can damage ginseng.

There are three products registered for control of cutworms on ginseng: Pounce, Coragen and Exirel. Coragen and Exirel are in the same insecticide group (Group 28) so they have a similar mode of action. If repeated applications are necessary, it is important to rotate between Pounce and either Coragen or Exirel.

Cutworms, like slugs, are mainly active at night. During the day, they bury themselves in the soil under the straw were they are unlikely to be contacted by insecticides. As a result, all three products are best applied in the evening close to or after dusk when they are active and they can be directly contacted by the product. If they are applied during the day, the cutworms may still be killed by feeding on plant tissues coated in the product, but they will have to cause damage before they can take up the product.  Also, products degrade faster under warm and sunny conditions, so efficacy would be reduced the longer the product is on the plant tissues before dusk. Pyrethroids like Pounce in particular degrade very fast under hot conditions. They are best applied when temperatures are more moderate.

The products are best applied at a water volume that ensures coverage of the stem and some run off down the stem to the soil surface. This is because the cutworms can feed on the stem below the straw. Moist conditions may be necessary for the cutworms to be active, so irrigation may be required before application to ensure the garden is moist. Overhead irrigation or rainfall should not occur after application for at least 24 hours because it will wash the product off of the plant tissues. Unlike fungicides for root disease control, these products and the registered application rates are not designed to control the cutworms when they are buried in the soil.

No other major issues have been reported on ginseng this week. Despite the rainfall yesterday, it remains very dry and it is important to monitor soil moisture closely to avoid unnecessary stress on the plants. In un-irrigated soil at the Simcoe Research Station, the 18 mm (0.7 in) of rain we received only penetrated about 10 cm (4 in.) into the soil with very dry soil beneath.

About Sean Westerveld

Ginseng and Medicinal Herbs Specialist, OMAFRA
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