The poinsettia plant is well known as a festive plant that is often given as a gift during winter holidays. Although the poinsettia is fairly easy to take care of, some problems can occur. One of the most common issues is a disease known as alternaria leaf spot. Treating this disease properly will help keep your poinsettia plant healthy for a long time.
The most common signs of alternatia leaf spot disease are brown or blackish spots on the leaves. These spots can start off small, but if left untreated, can grow to the size of the entire leaf. In its advanced stages, this disease can cause the leaves of your poinsettia plant to fall off. Alternatia leaf spot is not necessarily fatal, but if action is not taken for an extended period of time, the plant will eventually die.
The most important thing you can do when you first spot alternatia leaf spot is to remove as many of the affected leaves as possible. Because this disease is caused by a fungus, each spot is capable of spreading, so extensive pruning may be necessary. Once you have pruned the plant adequately, spray the poinsettia with a fungicidal spray to prevent any further growth.
Continue to monitor your poinsettia over the next few weeks. If you see any spots, prune immediately and then spray with fungicide again. However, take care not to spray with fungicide too much because it can be toxic to your plant in large quantities. If you have already sprayed your plant twice in a week, hold off three or four days before spraying again.
To keep this disease from occurring again, make sure to remove all plant debris from the bottom of the poinsettia pot and keep the plant healthy. Make sure it has access to partial sun and is watered regularly so it does not become susceptible to an outbreak of alternaria leaf spot again.