As the disease progresses, spots turn brown and angular and can be confused with poinsettia scab. Alternaria leaf spot is one of several fungal diseases that can pounce on your poinsettias when your attention is diverted.The pathogen, Alternaria euphorbiicola (or certain other Alternaria species) most likely travels along with poinsettia cuttings, and attacks when the environmental conditions favor infection. Until recently, it has been known to be a production problem only for poinsettias in Florida and Hawaii, where inoculum presumably survives from … However, poinsettias are susceptible to several diseases, mostly fungal and include root rot, root and stem rot, black root rot, scab, powdery mildew and blight. that spot leaves will also infect bracts. Whitefly . A festive houseplant during the winter holiday season, the poinsettia (Euphorbia pulcherrima) grows in U.S. Department of Agriculture plant hardiness zones 9 through 11. These pests can feed on many parts of the poinsettia plant or be associated with the production areas. Beware of this disease next year during poinsettia propagation season. Yellow or tan spots can develop across the leaf. As the disease progresses, spots turn brown and angular so could be confused with poinsettia scab. However, as a native to Mexico they can struggle to survive as a houseplant as it can be difficult to provide the right environmental conditions. Poinsettia scab is a spot anthracnose disease caused by the fungus Sphaceloma poinsettiae Jenk. Identifying Poinsettia Nutritional Disorders By Brian Whipker, Ingram McCall and Jared Barnes To view tables and figures, click on the PDF link to the right. & Ruehle (46,60). When poinsettia season comes, that also means the arrival of pests and diseases that affect the popular holiday crop. Yellow or tan spots can develop across the leaf. Poinsettia Insect & Mite Management A wide variety of insect and mite pests have been found in association with poinsettia production both in shade houses and in the greenhouse ( Table 1 ). Pathogens Root rot caused by Pythium is the most common disease affecting poinsettia production. Plant fertilization requirements, nutrient monitoring and nutrient disorders have been a major research and … & Ruehle (46,60). Phytophthora and Rhizoctonia can also rot the roots of poinsettias, and under favorable conditions, move upward to affect the stem and lower branches. Poinsettia pests and diseases Purchasing a pot grown Poinsettia is as much a part of modern Christmas celebrations as it is to buy a trimmed fir tree. A well-cared-for poinsettia can live for up to two years. So, it's a good idea to send samples to … Xanthomonas leaf spot on Poinsettias Symptoms of Xanthomonas campestris pv poinsettiicola begin with dull gray water-soaked areas. Botrytis is the primary disease affecting poinsettia stems, leaves and bracts at all stages of production. In the realm of insects and diseases, two of the most common poinsettia problems for growers are whitefly and Botrytis. Xanthomanas leaf spot on poinsettias begins with dull gray water soaked areas. Schlumbergera, commonly referred to as Christmas cactus, derives its common name from its winter bloom period. Each of the six Christmas cactus species produces a different colored bloom, with red being the most common. Beware: The Alternaria spp. As with all cacti and succulents, the Christmas cactus is susceptible to disease. Photos: Jim Barrett.