This disease, which very closely resembles Alternaria leaf spot, is caused by the fungus Cercospora zinniae. It should go without saying, that is a level tablespoon. Choose a location where your plants can receive direct sunlight. The disease causes a white to grayish powdery growth on the leaves. sticky "honeydew" (waste) on the stems (aphids) or tiny bugs that jump up off the plants as you disturb the leaves (leafhoppers). Amending the soil with compost will speed the flowering process. Note to readers: if you purchase something through one of our affiliate links we may earn a commission. They can be planted in the spring throughout Florida and also in the fall in South Florida. Some of the leaves have holes in them, and a few plants are turning brown and dying. If there's no sign of bugs and the leaves are just discoloring from white to brown, a fungicide spray would be the answer to mildew. They are usually spread by insects. Zinnias sometimes suffer from powdery mildew (Golovinomyces cichoracearum), a fungal disease that causes a white or grayish-white powdery growth to form on leaves, flowers and stems. Zinnias need full sun and well-drained soil. Various diseases caused by viruses occasionally attack zinnias. But most of the older varieties are so prone to mildew (and occasionally bugs) that I stick mainly with the compact new zinnia series 'Profusion' and 'Zahara.' Most fungicides you'll encounter in garden centers are labeled for mildew control. But zinnias are easy to direct sow and bloom fairly quickly from seed so direct sowing may be a better option for some gardeners. Plant after the last frost date and be sure to give them space; crowding encourages disease. How do I get my zinnias to bloom more? The holes could be due to Japanese beetles or to a couple of other smaller beetles that sometimes eat zinnia leaves. 'Crystal White' is another fine Mexican Zinnia with excellent disease resistance. De-stressing includes picking good varieties in the first place, growing them in good soil and the right light exposure, and keeping them watered in hot, dry weather -- and especially when young. Stem and root rot diseases cause black, mushy growth, and often kill zinnias. Q: My zinnias are really being wiped out this year. Bacterial leaf spot causes reddish brown, angular spots on the leaves and can cause plants to die out by mid-August. All are easier to prevent than to cure. Zinnia Leaves Are Turning Yellow White And Turn Crispy Starting From Outside Edges, Zinnia Leaves Have Holes And Thimble Sized Droppings On Them, Zinnia Leaves Have White A Spot With A Black Spot In The Center, Zinnia Leaves Are Looking Like Spider Webs, Zinnia Leaves Have Dark Veins And Are Curling, Zinnias Stayed Dried And Wilted Even After Watering, Zinnia Are Still Blooming But Leaves Are Turning Brown, Dark Red Zinnias Are Turning Pink And White, Benarys Giant Zinnia Stems Flop Over When Flowers Are Cut, Recently Purchased Plants Developing Fungus That Girdles Bottom Of Stem. Star Zinnias are varieties of Mexican Zinnia (Zinnia angustifolia). A: Zinnias can be prone to several bugs as well as the most common problem -- powdery mildew, which is a disease that turns the leaves whitish, then brown. Are they growing tiny because they are over crowded or because the seeds are just a small variety. I have definitely had an insect problem. The plants may show curled, distorted, mottled foliage, they may be stunted or deformed, wilting, turning yellow and then dying. Zinnias are sensitive to frost, so do not seed until the last frost has passed. Work some organic matter into well-draining soil before planting, aiming to achieve a soil pH between 5.5–7.5. They live until hard frost doesn’t kill them. These include fungal leaf spot, powdery mildew (which looks like someone sprinkled flour over your plants) and blight. But if your plant started out with faded color, it may be that it is lacking fertilizer or is seeing sunlight much more intense than it is use to. Sevin kills most bugs. Start planting them 2-3 weeks after frost. Can I grow zinnias as a houseplant? Thank you so much for your time! Registration on or use of this site constitutes acceptance of our User Agreement, Privacy Policy and Cookie Statement, and Your California Privacy Rights (each updated 1/1/20).