Conditions over the past week have been conducive for the development of Alternaria stem and leaf blight. Look for tan-coloured lesions along the stem that are brittle and eventually form black spores. Lesions on the leaves are often circular, tan in colour with a yellow halo and concentric rings. Alternaria will often develop first in older gardens next to infected stems from last year. Consult OMAFRA Publication 610 Production Recommendations for Ginseng and the 2012 Supplement for a list of products to control Alternaria.
Insect issues usually begin to affect ginseng at this time of year. Insects are often patchy problems in ginseng and do not always require a control. However, occasionally cutworms (Figure 1) four-lined plant bug (Figure 2), leaf rollers (Figure 3), and aphids (Figure 4) reach sufficient populations to warrant a control. These insects require close monitoring of gardens for early growth stages. By the time damage becomes noticeable in a ginseng garden, it may be too late to adequately control the pest. Spot application in problem areas may be sufficient for some insect pests. Aphids and the nymphs of four-lined plant bug are beginning to show up in the landscape and may affect ginseng over the next few weeks. Permethrin products (Pounce 384 EC, Perm-Up EC, Ambush 500 EC) are the only registered products for control of cutworms and four-lined plant bug in ginseng (Only four-lined plant bug for Ambush 500 EC). Dipel 2X DF is the only product registered for control of leaf rollers. Beleaf 50SG is the only product registered for control of aphids in ginseng. Consult the product label before applying any pest control product.
Figure 1. A severed top lying upside-down on the straw is a common symptom of cutworm feeding.
Figure 2. Nymphs of four-lined plant bug are red with black wing pads, move rapidly when approached, and cause small circular windows in leaves.
Figure 3. A leaf roller caterpillar on ginseng. Normally these are protected in rolled leaves but they come out at night to feed.
Figure 4. Aphids often line the stem of the developing flower head.