2017 ASHS Annual Conference

In the past few years the number of orchids infected with Fusarium has increased tremendously. There are over 10 species that have been associated with different orchid genera. Eight have been confirmed as pathogens and a few more need to be tested. The symptoms caused these Fusarium species include: leaf spots, large rots, and kill of the leaves; bulb spots and loss of bulbs; flower spots and rots; spots on young shoots and loss of shoots; Cane or pseudostem rots; root rots and plant decline; Fusarium diseases have been found on Dendrobium species, Cymbidium, Cattleya and hybrids, Miltonia, Odontoglossum, Epidendrum, Oncidium, Phalaenopsis, Vanda, and many others. Intergenerics are also infected. Seedlings growing close together share diseases with ease, as splashing water spread the spores from one plant to another. Tissue infected with Fusarium form spores on the outside of the plant. These spores are splashed from one area to another or one plant to others. As long as the environment is moist, the spores will germinate and penetrate the new clean plant. It will penetrate the epidermis and grow internally. The fungus feeds on the host plant and many parts are killed. Seedlings are easily infected and many die from Fusarium diseases. These diseases may resemble those caused by Pythium or Phytophthora. To control these diseases, avoid purchasing weakened or disease plants. Check for healthy roots if possible. Fungicides can be used and thus far, Rally (myclobutanil) is effective but must be sprayed before infection. Keep the environment dry and if possible water early in the morning and not in the late afternoon, to prevent moisture during the night. Remove any dead or dying plants, as well as diseased leaves and flowers.