Q. A blight or mildew appeared on the leaves of my phlox last spring. Spraying them with bug-killer has not helped. I'm hoping you have a remedy to stop it from appearing. - F.L., Charlevoix, Mich.
A. Judy Lowe, an experienced gardener of Chattanooga, Tenn., says your bug spray had no effect because powdery mildew is a fungus; it isn't caused by insects. Phlox is very mildew-prone, so if you want to continue to grow this colorful flower, preventive measures will need to be taken each year. Using one or more of these methods should take care of it:
*Increase air circulation around the plants by digging up crowded clumps and replanting them farther apart. If plants tend to flop over, stake them so they're upright and not touching each other.
*Plant phlox where they receive more sunlight.
*Use less fertilizer or fertilize only with a low-nitrogen plant food.
*Water at the base of the plants so that the leaves don't get wet.
*Spray weekly with sulfur or another fungicide from early spring until the flowers fade. Read and follow the label directions carefully. (Sulfur can burn plants when the weather is very warm.)
*After phlox have finished blooming, stop spraying and cut back the plants if mildew develops, in order to stop the spores from spreading. Dispose of the mildewed cuttings away from the garden.
*Replace the plants with a variety of phlox that is mildew-resistant.
*If mulch is used, make sure it's not right up against the stems of the phlox. Remove mulch that was around the mildew-infected phlox last year, and replace it with new mulch.
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