Symptoms of Parsnip Powdery Mildew
While powdery mildew affects many plants, it can be caused by a number of different fungi, many of which target only certain plants. For example, parsnips with powdery mildew are infected specifically by Erysiphe fungi. Erysiphe heraclei, in particular, is often a culprit. Powdery mildew symptoms start as small, white spots on both or either side of the leaves. These spots spread to a fine, sooty coating that can cover the entire leaf. Eventually, the leaves will turn yellow and fall off.
How to Manage Parsnips with Powdery Mildew
The best method for dealing with parsnip powdery mildew is prevention. Space your parsnips so the leaves of neighboring plants aren’t touching, and plant them in rows so that prevailing winds travel down the rows and provide good air circulation. Allow two years to pass between planting parsnips in the same spot, and plant in soil with a slightly high pH (about 7.0). Remove infected leaves or plants to prevent the fungus from spreading. Spraying preventative fungicides can sometimes be effective, but it’s usually not required if these other less invasive measures are taken. As a rule, parsnips are not especially susceptible to powdery mildew and aggressive fungicide application is not necessary. Some varieties of parsnip are tolerant of the fungus and can be planted as a preventative measure if powdery mildew is a particular problem in your garden.
