We have been finding a significant amount of aphids in ginseng fields over the past few weeks. They have been found on all ages of ginseng and several areas of the ginseng growing region. Look for aphids on the underside of the leaves and along the petioles of the leaflets (Figure 1). They can often be found clustering on the midrib of the leaflet or along a vein. Aphids are sucking insects that stay relatively stationary on the leaves. The sucking removes sugars from the plant and can reduce energy needed for root growth if populations reach sufficient levels. Aphids can be best identified by their two cornicles that look like tail pipes extending from the rear of their body (Figure 2). This species is completely green with brownish legs. Winged aphids will have the wings folded straight back from their bodies. They cannot be easily confused with any other pest of ginseng.
Figure 1. Aphids on the underside of a ginseng leaf.
Figure 2. Closeup of an aphid feeding on the midrib of a ginseng leaf.
There are no thresholds for aphids in ginseng that would indicate when it is necessary to spray, but populations seen so far probably do not warrant an insecticide application. At this time of year, yield may not be impacted until populations reach in the hundreds per plant, except on seedlings where fewer would be necessary to cause damage. Even on seedlings, dozens of aphids per plant would probably be necessary to warrant a spray this late in the season. Spray is also warranted when there are obvious visual effects on the health of the canopy due to aphid feeding. A localized spray with a backpack sprayer may be all that is needed to control hot-spots in the garden. The existence of aphids in gardens at this time does not mean the population will be elevated next season. Aphids are only occasional pests of ginseng and aphids will probably leave the garden for overwintering.
Other insect pests and diseases of ginseng are at typical levels for this time of year, except for hot spots of disease in areas where excessive rain fell over the past few weeks. It is still important to monitor soil moisture at this time of year because some areas did not receive nearly as much rain, and irrigation may be necessary. Cooler weather conditions this year should delay leaf senescence and result in higher root growth and improved seed development.