Managing Powdery Mildew on Poinsettia
Powdery mildew is a fungal disease of poinsettia caused by Oidium sp. Powdery mildew can occur on all above ground plant parts and results in a white, powdery or fluffy appearance. While severe infection can cause yellowing and withering of leaves, even a light infection can render plants unmarketable. The first colonies of powdery mildew can occur on the undersides of the lower leaves where they may escape detection until the environment is favorable for rapid production of conidia (spores). Once conidia are produced in large quantities, the disease spreads rapidly and becomes evident to growers. When powdery mildew “explodes,” it is difficult for even a highly effective fungicide to control this disease. Also, the white fungal colonies present before the fungicide treatment will remain on the plant surface and are unsightly. Since fungicide applications to colored bracts can result in phytotoxicity or residue, it can be helpful to use a long lasting fungicide just prior to bract coloration.
Source: • American Floral Endowment Research Reports #118
Keywords: Powdery Mildew