What does downy mildew look like?
Downy mildew looks very different depending on the specific plant, weather, fungicide use and sometimes the species of fungus involved. The most common symptoms are yellow or tan, angular or blotchy spots that appear on the upper leaf surface. Leaf distortion also occurs giving spots a blistered, pale look (common on pansy). On the undersides of the leaves, the white, lavender or purple spores of the pathogen form a “downy” patch between the leaf veins. Occasionally, the spores form all over the leaves. This happens frequently with alyssum, giving plants the appearance of being sprinkled with salt or sugar. In some cases, like with snapdragons, a systemic infection can occur with severe stunting and distortion of the final appearance. Rose downy mildew is remarkably variable. In the past 10 years the most common symptom has been angular, tan spots with a very small amount of white crystalline sporulation on leaf undersides. The name of the pathogen is Peronospora sparsa — a name that r
