Any proprietary fungicide containing Captan or Mancozeb are effective for controlling both mold and mildew. As before, a weaker than recommended solution is advisable, regardless of brand. Unlike insecticides, fungicides may be sprayed at regular set intervals as a precautionary measure. If either disease appears, spray trees immediately with fungicide. The placement of bonsai is another important factor in their success.
Hardy bonsai do best if grown outside as long as possible.
They can even be left outside in the winter and allowed to go dormant as long as they are protected from our harsh winters. Some species need cold conditions to induce dormancy and to enable the trees to shed leaves, or to produce flowers and fruit. If varieties such as Japanese maples, crab apples, larch and beech do not have cold conditions, they will be unable to go through their natural growing cycles, and will thus soon weaken and die. Tropical Bonsai can be grown outdoors in the summer as long as they are shaded from the hot sun. They must be brought indoors before frost and placed in a warm, well lighted area.