With the hot, humid weather over the past few days, Alternaria is reportedly showing up in many older gardens. Most of the damage is within the canopy and along the stems. This is where it is most difficult to reach with fungicide sprays. A combination of timely sprays, a rotation of effective products and good spray coverage are necessary to keep Alternaria under control. Studies lead by OMAFRA’s Sprayer Technology Specialist Dr. Jason Deveau have shown the importance of drop nozzles down each row for achieving good covered of the stems within a dense canopy. Consult the following two resources for more information on achieving the best spray coverage.
Given the shortage of chlorothalonil products (Bravo/Echo) this year, growers should pay particular attention to their spray rotation. Chlorothalonil provides a broader spectrum of disease control than many alternatives. However, some of the alternatives are actually better than chlorothalonil at controlling specific diseases. Products will have to be chosen more carefully to match the diseases that have the highest risk at the time. Right now, the highest risk is Alternaria and products most effective on this disease should be chosen.
Many species of insects are also starting to emerge in ginseng including cutworms, leafrollers and grubs (seedlings). Four-lined plant bug nymphs have also emerged on other crops and may be present in ginseng. At this time of year with warm temperatures and young tender growth, scouting fields at least twice a week can catch insect problems when the insects are small and still susceptible to insecticides. Some insects could develop enough in a week to go from eggs to a stage where it is too late to get effective control. For most insect pests, insecticides are only necessary if they reach high levels. Localized sprays may be sufficient to control these pests since they tend to be patchy.