Alternaria and Botrytis (Figure 1) continue to be the biggest issues in ginseng at this time in gardens damaged by frost. It is important to continue spraying for both diseases on a tight rotation. Once weaker plants die off and plant tissues harden, the risk of Botrytis will gradually decline. The risk of Alternaria will likely remain all season but with wider spray intervals once active infections are controlled.
With the heavier rains over the past two weeks, the risk of foliar Phytophthora has increased. Foliar Phytophthora will show up first in areas of the garden with a history of the disease, especially in areas with standing water or where soil is uncovered. Spores of the pathogen can splash onto the leaves in these areas. The best way to reduce the chances of the disease developing in these areas is to subsoil to allow drainage of excess water and to cover exposed soil and any remaining standing water with straw, wood chips or gravel to reduce the potential for splashing. Avoid driving or walking through areas with muddy soil or standing water to avoid spreading spores down the trenches.
This is the time of year when leafrollers begin to show up in ginseng gardens. However, most growers do not notice them until the damage has already been done. It is important to scout gardens carefully at this time for curled up leaves and minor feeding damage. Damage is usually more prevalent close to woodlots. Uncurling the leaves should reveal some webbing and a small caterpillar. The insecticide will only be beneficial when the caterpillars are young. They are usually only needed in localized areas of the garden because leafrollers tend to be very patchy. Dipel 2X DF is the only insecticide registered for use on leafrollers. The caterpillars will pick up the insecticide when they feed at night. Direct contact of the caterpillar is not required with this product.