Given that poinsettias are propagated during the hottest months of the year and have a very long production time, they are prone to several pathogens, pests, and physiological disorders. Occasionally, greenhouse growers observe irregularities on the leaves or stems of their crops that are not caused by insects or diseases. Environmental factors during both propagation and production, such as drought stress, exposure to high light or temperatures, or changes in relative humidity, can all cause poinsettia leaf abnormalities, distortion, crippling, or puckering. These issues are often the most difficult to diagnose as you cannot isolate the problem in a petri dish or visually observe an insect or pathogen.
Recent reports of leaf abnormalities align with the traditional occurrence of these symptoms that often occur from mid-September to early October. Poinsettia leaf distortions (Figure 1) often occur on young or immature leaves and are believed to be caused by many factors.
Leaf and meristem distortions can be caused by herbicide exposure, but if you can rule out an exposure there are many environmental and cultural factors that can lead to leaf distortions. Physical damage during pinching, ruptured cells and latex residue can cause the expanding leaf to become distorted. Therefore, care should be taken to avoid latex from dripping onto the plant during pinching.
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