Downy mildew—Peronospora destructor
The first evidence of downy mildew is a fine, furry, grayish white to purple growth on the surface of
older leaves. Leaf tissue under the growth becomes pale green, then yellow, and finally collapses. Large,
yellowish, circular clumps of infected plants may be the first symptom noticed in the garden. The yellowing
patterns often enlarge in the direction of prevailing winds.
Use disease-free bulbs, sets, and seed. Use a 3-year rotation away from onions, garlic, and related crops
where the disease has occurred. Destroy volunteer and diseased plants. Well-drained soil, freely circulating
air, and allowing plants to dry between irrigations help prevent the disease.
growth of downy mildew