Cause:
Blumeriella jaapii (formerly Coccomyces hiemalis), a fungus. It overwinters on fallen cherry leaves and in spring produces large numbers of spores from the previous year's leaf infections. Air currents and rain move spores. In spring, with moisture, they initiate new infections on young leaves through the stomata. Once unfolded, leaves are susceptible throughout the growing season, but susceptibility decreases with age.
The disease is particularly severe on sour cherries, but also attacks sweet cherries in western Oregon and Washington. It is especially a problem in recently planted orchards that are not being sprayed for brown rot control. Resulting losses are associated with a weakening of the tree as a result of early summer defoliation.
Symptoms:
On the sour cherry leaves, variously colored spots develop on the upper surface. The spot or lesion rapidly enlarges, becoming brown or purple, and dies from the center out. Infected spots are irregular or round and are over the entire leaf surface. Individual spots never become large. They merge together to kill large areas of the leaf. Spot development precedes yellowing and leaf dropping. The area adjacent to the spot may remain green while the rest of the leaf turns yellow. Diseased leaf tissue may separate from healthy tissue, drop out, and give the leaf a shothole appearance.
On sweet cherry leaves, spots often are larger and nearly circular. Cream-colored spore masses of the fungus appear on the lower leaf surface associated with the spots on both sweet and sour cherries. On fruit stems, infections sometimes girdle the stem to cause a fruit drop. While infections occur on the fruit, they are less common than on foliage.
Notice the sporulation of cherry leaf spot fungus in both leaf and stem lesions.
Infected leaves turn yellow and fall off.
Cultural
control: Rake up and destroy infected leaves.
Chemical
control: Apply a fungicide at petal fall, shuck fall, and 2 weeks later. Postharvest applications are helpful in wet years. Rotate or tank-mix materials to prevent resistant strains from developing. Fungi resistant to group 3 fungicides have been detected in Michigan. A forecasting program is available from Michigan to help time applications. Tests in western
Oregon show the program is useful at higher temperatures.
Bravo Weather Stik at 3 to 4.1 pints/A. Do not apply after shuck split but may be used after harvest. Do not use more than 20.5 pints/A/season. Generally excellent control. Ortho Daconil Multi Purpose Fungicide is registered for home use. 12-hr reentry.
Captan 80 WDG at 1.9 to 2.5 lb/A. Applications may be made day of harvest. For home use but only available with other chemicals in pre-packaged mixes. Generally good control. 24-hr reentry.
CaptEvate 68 WDG at 3.75 lb/A Do not apply more than two (2) consecutive application or more than 18.75 lb/A/season. Can be used day of harvest. 24-hr reentry.
Echo 720 at 3.1 to 4.1 pints/A. Do not apply after shuck split. 12-hr reentry.
Elite 45 DF at 4 to 8 oz/A. Do not apply more than 3 lb/A per crop season. Can be applied up to and including day of harvest. Generally good control. 12-hr reentry.
Gem at 4 to 8 oz/A. Rotate with other fungicides that have different modes of action. Do not apply more than twice consecutively, exceed four (4) applications, 32 oz/A/season, or within 1 day of harvest. Do not use with ogranosilicate surfactants. ‘Concord’ grapes may be injured if accidentally sprayed. 12-hr reentry.
Indar 2F at 6 fl oz/A plus a wetting agent. Do not apply more than 48 fl oz/A/season. Generally good control.
12-hr reentry.
Orius 45 DF at 4 to 8 oz/A. Can be applied through the day of harvest. 12-hr reentry.
Pristine at 10.5 to 14.5 oz/A. Do not use more than 2 consecutive applications or more than 5 times/year. Can be used day of harvest. 12-hr reentry.
Procure 480 SC at 10 to 16 fl oz/A. Do not apply within 1 day of harvest or more than 96 oz/A/year. 12-hr reentry
Propiconazole-based fungicides are registered. Limited to four (4) applications (2 during bloom and 2 before harvest). May be used up to and including day of harvest. In the Willamette Valley, smaller, deeper green leaves have been observed on ‘Royal Ann’ cherry trees treated with a dilute application at 3 oz/A.
Bumper 41.8 EC at 4 oz/A. Do not use on Stanley-type Plums. 24-hr reentry.
Orbit at 4 oz/A. Do not use on Stanley type Plums earlier than 21 days before harvest. 12-hr reentry.
PropiMax EC at 4 fl oz/A. Do not use on Stanley-type Plums earlier than 21 days before harvest. 24-hr reentry.
Tilt at 4 fl oz/A. Do not use on Stanley type Plums earlier than 21 days before harvest. 12-hr reentry.
Quilt (propiconazole + azoxystrobin) at 14 fl oz/A. Do not apply more than two (2) sequential sprays. May be applied the day of harvest. 12-hr reentry.
Rally 40 WSP at 2.5 to 6 oz/A. Use Eagle 20 EW at 2 to 3 fl oz/100 gal water for landscape use. Can be applied up to day of harvest. Has eradicant activity. Generally excellent control. 24-hr reentry.
Rubigan EC at 6 to 12 oz/A. May be applied from late bloom up to harvest. Do not apply more than 48 oz/A per season. Generally excellent control. 12-hr reentry.
Spectracide Immunox at 0.5 fl oz/gal water. Can be applied up to and including the day of harvest. Do not use more than 7 times per year.
Sulfur, flowable (52%) at 5 gal/A. May be phytotoxic if applied at temperatures above 85oF. Generally fair control. 24-hr reentry.
Syllit FL at 1 to 3 pt/A. 48-hr reentry.
Topsin 4.5 FL at 22.5 to 30 fl oz/A.. Do not apply within 1 day of harvest. This material may kill earthworms which help decompose infected leaves. Halt (by ferti-lome) is registered for home use. 12-hr reentry.
Ziram 76 DF at 6 lb/A. Do not use within 30 days of harvest. Generally fair control. 48-hr reentry.
Notes:
Although effective, copper products are not recommended due to phytotoxicity to fruit.
References: Eisensmith, S.P. and A.L. Jones. 1981. Infection model for timing fungicide applications to control cherry leaf spot. Plant Disease 65:955-958.
Content edited by:
Jay W. Pscheidt on
January 1, 2009
