Dogwood leaves have a mildew look..They

landdawg(8)June 5, 2008

don't look like the 2 diseases described on the UGA website. The leaves look normal as far as shape and the leaves aren't curling or anything. They just have some discoloration and they look like they have mildew on them. Am I watering them too much? I only water them once/twice a week.

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My dogwood's leaves look just the same (well, the ones on the lower limbs of the tree, the upper leaves seem unaffected so far).

Mine is a Kousa dogwood (i think, although it did not flower this year). What kind is yours? I've never watered ours.

I don't know what it is either and was going to post the same question.

    Bookmark   June 5, 2008 at 10:11AM
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Nearly everyone can appreciate the beauty of a flowering dogwood tree. The native Kentucky tree often is the victim of some nasty pests. Now it faces the adversity of powdery mildew.

"Powdery mildew symptoms may appear in mid-summer, long before the white powdery spores of the fungus, that causes the disease, are visible." Extension Plant Pathologist for the University of Kentucky College of Agriculture, John Hartman said. "Affected parts of leaves develop a mottled yellowing, or turn light green or yellow and develop brownish patches."

Hartman also said in some cases, the fungus is barely visible, yet in others it is more prominent. The disease can begin as light, reddish-brown or irregular purple blotches on the dogwood's leaves, which eventually turns to dark brown to tan patches.

Powdery mildew progressively increases from early June to early September. The most severely affected trees could be wilted and brown by late summer and the youngest leaves may be distorted and curled.

"Although it would appear to weaken trees," Hartman said. "Powdery mildew does not appear to be lethal. We have observed that under high disease pressure, flower production is decreased the following year."So, what can Kentuckians do to help out the dogwood's plight? Hartman said to avoid cultural practices that stimulate succulent growth, such as applying nitrogen fertilizer, heavily pruning and excessively irrigating. Also, apply mulch over the root system, prune out dead branches, and provide good air movement and light penetration by judicious pruning of nearby vegetation.

Do your part by planting dogwood species that resist powdery mildew, such as oriental dogwoods and cultivars. Make sure future generations can enjoy the beauty of dogwood trees in Kentucky.

Writer: Aimee D. Heald (606) 257-9764

Source: John Hartman (606) 257-5779

    Bookmark   June 5, 2008 at 10:24PM
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the thing I need???? Thanks alot for your help, I just called the feed/seed store and they have it.

    Bookmark   June 6, 2008 at 8:04AM
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Here is a pic of my dogwood's leaves -- Landdawg do yours look the same? Vroomp, is this powdery mildew? I dont have any discoloration or brownish spots, just this white stuff.

Only the leaves near the bottom of the tree have it, the ones at the top look healthy. Do you think I should cut off the affected branches?

Thank you!

    Bookmark   June 7, 2008 at 3:15PM
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Ohio State University Extension Fact Sheet
Plant Pathology
2021 Coffey Road, Columbus, OH 43210-1087


Powdery Mildews on Ornamental Plants
Stephen Nameth
Jim Chatfield
Almost all landscapes have plants that become diseased with one of the powdery mildew fungi. Although the fungi that cause powdery mildew are usually different on different plants, all of the powdery mildew diseases are similar in appearance. In most cases, prompt recognition and control actions can prevent severe damage to plants from powdery mildew diseases.

Powdery mildews, as the name implies, often appear as a superficial white or gray powdery growth of fungus over the surface of leaves, stems, flowers, or fruit of affected plants. These patches may enlarge until they cover the entire leaf on one or both sides. Young foliage and shoots may be particularly susceptible. Leaf curling and twisting may be noted before the fungus is noticed. Severe powdery mildew infection will result in yellowed leaves, dried and brown leaves, and disfigured shoots and flowers. Although it usually is not a fatal disease, powdery mildew may hasten plant defoliation and fall dormancy, and the infected plant may become extremely unsightly. On roses, uncontrolled powdery mildew will prevent normal flowering on highly susceptible cultivars.

Powdery mildew fungi infect almost all ornamental plants. They are commonly seen only on those plants more naturally susceptible to the disease. Susceptible woody plants include some deciduous azaleas, buckeye, catalpa, cherry, a few of the flowering crabapples, dogwood, English oaks, euonymus, honeysuckle, horse chestnut, lilac, privet, roses, serviceberry, silver maple, sycamore, tulip tree, some viburnums, walnut, willow and wintercreeper. Powdery mildews are also common on certain herbaceous plants, such as chrysanthemums, dahlias, delphiniums, kalanchoes, phlox, Reiger begonias, snapdragons and zinnias. Remember that each species of powdery mildew has a very limited host range. Infection of one plant type does not necessarily mean that others are threatened. For example, the fungus that causes powdery mildew on lilac does not spread to roses and vice versa.

Environment Favoring Powdery Mildews
Most powdery mildew fungi produce airborne spores and infect plants when temperatures are moderate (60 to 80 degrees F) and will not be present during the hottest days of the summer. Unlike most other fungi that infect plants, powdery mildew fungi do not require free water on the plant surface in order to germinate and infect. Some powdery mildew fungi, especially those on rose, apple, and cherry are favored by high humidities. Overcrowding and shading will keep plants cool and promote higher humidity. These conditions are highly conducive to powdery mildew development.

Control of Powdery Mildews
Before using fungicides you should attempt to limit powdery mildews by other means. The following cultural practices should be beneficial for controlling powdery mildews.

Purchase only top-quality, disease-free plants of resistant cultivars and species from a reputable nursery, greenhouse or garden center. Horticulturists in the green industry and Extension offices should be consulted concerning the availability and performance of resistant varieties.

Prune out diseased terminals of woody plants, such as rose and crabapple, during the normal pruning period. All dead wood should be removed and destroyed (preferably by burning). Rake up and destroy all dead leaves that might harbor the fungus.

Maintain plants in a high vigor.

Plant properly in well-prepared and well-drained soil where the plants will obtain all-day sun (or a minimum of 6 hours of sunlight daily).

Space plants for good air circulation. DO NOT plant highly susceptible plants--such as phlox, rose, and zinnia--in damp, shady locations.

Do not handle or work among the plants when the foliage is wet.

Water thoroughly at weekly intervals during periods of drought. The soil should be moist 8 to 12 inches deep. Avoid overhead watering and sprinkling the foliage, especially in late afternoon or evening. Use a soil soaker hose or root feeder so the foliage is not wetted.

Chemical Control of Powdery Mildews
In many cases, powdery mildew diseases do little damage to overall plant health, and yearly infections can be ignored if unsightliness is not a major concern. For example, lilacs can have powdery mildew each year, with little or no apparent effect on plant health. On some plants, powdery mildews can result in significant damage. Thus, fungicides must be used to achieve acceptable control. For best results with fungicides, spray programs must begin as soon as mildews are detected. Spray on a regular schedule, more often during cool, damp weather. Use a good spreader-sticker with the fungicides. Be sure and cover both surfaces of all leaves with the spray. Fungicides generally recommended for powdery mildew control include: Triadimefon (Bayleton, Strike); Triforine (Funginex), Thiophanate-methyl (Cleary's 3336, Domain) and Propiconazole (Banner).

Click here for a PDF version of this Fact Sheet.


All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.

Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.

TDD No. 800-589-8292 (Ohio only) or 614-292-1868


: Ohioline : Search : Fact Sheets : Bulletins :

    Bookmark   June 11, 2008 at 8:56AM
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Thank you so much, Vroomp, this is really helpful (shame-faced...I could have found this by Googling myself).

I will cut off the affected branches and hope it hasn't spread.
Thank you.

    Bookmark   June 12, 2008 at 9:55AM
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