Pythium and Phytophthora belong to a special group, so direct treatment must be done with special fungicides. Effective substances to control Pythium species are Propamocarb and Metalaxyl-M. Metalaxyl-M, Fosetyl or Dimethomorph can be used to control Phytophthora.
Plants showing symptoms must be removed from the stand immediately.
Endangered stands should not be sprayed with water as this might help the zoospores to spread quickly, in companies with recycled water the pest might spread via the roots.
Cultivation vessels, shelves, greenhouse tables and tools that were in contact with infected plants or water must be disinfected.
To prevent infection, cultivation conditions must be improved. In addition to avoiding high temperatures (early shading required) water treatment must be done carefully. Humidity may only be increased moderately.
Stagnant moisture is not to be expected in orchid substrates, but the substrate used for Phytophthora prophylaxis needs to meet certain requirements. The substrates used should not warm up too much, which would lead to the considerable weakening of plants in extreme conditions and contribute to spreading the disease more quickly.
