Often poinsettias are sold in a paper or plastic sleeve, but they should not remain sleeved any longer than necessary. Ethylene gas can accumulate within the sleeve and cause premature flower drop and leaf curling. Leaf drop is a common malady in poinsettias. They can be found either on the plant or soil surface. The adults are more of a nuisance, while the larvae tend to feed on plant tissue.
Mealybugs are serious pests of poinsettias.
These insects are soft-bodied and appear as a cottony mass, usually in the axis of the leaves. Most serious diseases that affect poinsettias are soil-borne and are primarily fungi. Species of Rhizoctonia, Pythum and Phytophthora are the most common diseases. The easiest methods for controlling these disease organisms are by sanitation and periodic soil drenches with a recommended fungicide. Reflowering Many of the new poinsettia cultivars will keep their leaves and remain attractive even in summer.