Root, crown, and stem rot caused by the fungus Rhizoctonia solani is a problem in the early to mid - stages of Poinsettia production. In most cases the fungus as a lesion or sunken area at the base of the stem (crown area) (Photo 1) . Under ideal conditions ( warm and wet) the fungus can move rapidly up the stem and result in complete girdling of the stem and sudden wilt of the plant (Photo 2) . If left unchecked the fungus will move down into the roots and cause root rot. Usually the stem symptoms are the first to be seen. By the time that the fungus reaches the roots significant damage has already occurred on the stem. It is easy to distinguish Rhizoctonia stem and root rot from that induced by Pythium sp. because Pythium root rot tends to start at the ends of the root tips and Rhizoctonia at the base of the stem.
In order to manage Rhizoctonia avoid over watering and allowing plants to become too warm. A variety of excellent chemicals are labeled for the control of Rhizoctonia root rot. These include Banrot, Chipco 26019 (iprodione), Cleary's 3336, Domain, Systec, (thiophanate - methyl), Benefit (thiophanate - methyl + iprodione), and Terraguard (triflumazole).
