|I have old fashioned perennial phloxs. Each year they get white and powdery leaves and stems. What can I spray or do to stop that from happening and why does it happen? Tnaks, Elaine|
|Powdery mildew and phlox see to go hand in hand. There are some disease resistant cultivars on the market so if you continually have a problem with powdery mildew, you might want to consider planting some more resistant types such as David (white), Orange Perfection (dark salmon), Prime Minister (white, red eye), and Starfire (red). Good cultural practices will help your plants avoid the disease, including spacing the plants adequately to allow good air movement throughout the foliage; watering the plants early in the day so leaves dry quickly; be careful not to over fertilize (especially with nitrogen); and remove diseased plant debris at the end of the season to minimize survival of the fungus over the winter.
In addition to these good cultural practices, regular fungicide sprays can be used to protect the leaves of the plants. Spraying will not cure the disease, so the fungicide must be applied early and repeatedly according to the directions of the label of the product purchased.
Good luck with your phlox.