Nurserymen and landscapers should consider using scab resistant crabapple varieties. The following is more information.
Use scab-resistant or scab-immune crabapples in the landscape. Scab immune trees don’t get scab while scab resistant trees may show some lesions, but not enough to cause defoliation. Nurserymen should be growing scab-immune or scab-resistant crabapples; these may include the following: these may include the following: ‘Adirondack’, ‘Bob White’, ‘Brandywine’, ‘Callaway’, ‘Camelot’,‘Candymint’,
‘Canterbury’, ‘Christmas Holly’, ‘Cinderella’, ‘Coralburst’, ‘David’, ‘Dolgo’, ‘Evereste’, ‘Excalibur’, ‘Firebird’, ‘Foxfire’, ‘Golden Raindrops’, ‘Guinevere’, ‘Hamlet’, ‘Holiday Gold’, ‘King Arthur’, ‘Lancelot’, ‘Lollipop’, ‘Louisa’, ‘Manbeck Weeper’, ‘Mary Potter’, ‘Molton Lava’, ‘Pink Princess’, ‘Prairifire’, ‘Prairie Maid’, ‘Professor Sprenger’, ‘Purple Prince’, ‘Rawhide’, ‘Red Jewel’, ‘Sentinel’, ‘Silver Moon’, ‘Sinai Fire’, ‘Strawberry Parfait’, ‘Sugar Tyme’, ‘Tina’, ‘White Angel’, ‘Winter Gem’, M. baccata ‘Jackii’, M. floribunda, M. sargentii, M. x zumi ‘calocarpa’.
Do not grow these in the nursery or plant in the landscape:
Very susceptible: ‘American Masterpiece’, ‘American, Triumph’, ‘Harvest Gold’, ‘Indian Magic’, ‘Jewel Berry’, ‘Pink Satin’, ‘Red Jade’, ‘Royal Scepter’, ‘Spring Snow’, ‘Thunderchild’, ‘Weeping Candied Apple’, ‘White Cascade’.
Extremely susceptible: ‘Almey’, ‘Eleyi’, ‘Hopa’, (there are others).
Information from the University of Kentucky.
Showing posts with label scab. Show all posts
Showing posts with label scab. Show all posts
Friday, May 29, 2009
Friday, May 22, 2009
Landcape - Current Diseases in the Landscape
The following is information on current diseases in the landscape from Bob Mulrooney, Extension Plant Pathologist, UD.
This is turning out to be an exciting year for plant pathologists--diseases springing up everywhere (pun intended). Look for scab, frog-eye leafspot and cedar-apple rust (bright orange lesions) on susceptible crabapple cultivars. Frogeye or Phyllosticta leafspot on red maple, silver maple and boxelder (irregular tan spots withred-brown margins--a minor disease rarely requiring control). Anthracnose, booming due to the cool wet weather can be found on sycamore, ash (same fungus causes anthracnose on Chinese fringe tree--look for curled, deformed leaves or leaflets and brown necrotic areas), even on oak leaves in the understory (producing large brown blotches and small irregularly shaped spots). Each host has its own specific anthracnose fungus. These diseases are usually not serious enough to warrant fungicide control.
This is turning out to be an exciting year for plant pathologists--diseases springing up everywhere (pun intended). Look for scab, frog-eye leafspot and cedar-apple rust (bright orange lesions) on susceptible crabapple cultivars. Frogeye or Phyllosticta leafspot on red maple, silver maple and boxelder (irregular tan spots withred-brown margins--a minor disease rarely requiring control). Anthracnose, booming due to the cool wet weather can be found on sycamore, ash (same fungus causes anthracnose on Chinese fringe tree--look for curled, deformed leaves or leaflets and brown necrotic areas), even on oak leaves in the understory (producing large brown blotches and small irregularly shaped spots). Each host has its own specific anthracnose fungus. These diseases are usually not serious enough to warrant fungicide control.
Friday, April 18, 2008
Landscape and Nursery - Crabapple Scab
Consider fungicide applications for control of crabapple scab on susceptible varities. The following is an article on the subject.
CRABAPPLES are pushing new growth now, some are approaching bloom, if very good control is needed on susceptible crabapples now is the time to begin fungicide applications for crabapple scab. Commercial applicators can apply Banner Maxx, Systhane, Daconil 2787, Cleary's 3336 (thiophanate-methyl), or any of the mancozeb fungicides beginning now at 7-14 day intervals depending on the label directions. Crabapple scab does not kill trees but can defoliate them prematurely if weather conditions favor infection throughout the season. The most effective chemical control is preventative fungicide applications before infection takes place during this time of year. Many landscape situations do not require heavy fungicide use and the use of resistant cultivars is always encouraged.
By Bob Mulrooney, Extension Plant Pathologist, UD
CRABAPPLES are pushing new growth now, some are approaching bloom, if very good control is needed on susceptible crabapples now is the time to begin fungicide applications for crabapple scab. Commercial applicators can apply Banner Maxx, Systhane, Daconil 2787, Cleary's 3336 (thiophanate-methyl), or any of the mancozeb fungicides beginning now at 7-14 day intervals depending on the label directions. Crabapple scab does not kill trees but can defoliate them prematurely if weather conditions favor infection throughout the season. The most effective chemical control is preventative fungicide applications before infection takes place during this time of year. Many landscape situations do not require heavy fungicide use and the use of resistant cultivars is always encouraged.
By Bob Mulrooney, Extension Plant Pathologist, UD
Friday, December 21, 2007
Greenhouse - Scab on Poinsettia
Scab can be a disease problem on poinsettia. Fortunately it does not show up each year. The following is an article on this disease.
Scab is a type of fungal disease called a “spot anthracnose”, which means that the pathogen, Sphaceloma poinsettiae, will cause tiny round spots and will be splashed about to start new infections if leaves sit wet for long periods. The disease does not appear to be widespread this year, but it is a good idea to review the symptoms so that you can keep a watchful eye on your crop.
Although scab can cause alarm because it is unfamiliar—it is not a disease that occurs every year without fail (like Botrytis!)—it is actually very nicely controlled via fungicides and cultural adjustments. The trick is to notice that it is present in the crop, so that the diseased plants may be promptly rogued out and the neighboring plants treated for their protection.
Often it is the growing areas with the highest amounts of leaf wetness where scab disease symptoms appear. Long periods of leaf wetness are needed for infection. Adjusting cultural procedures so as to reduce the length of time the foliage sits wet is important: water early in the day, use fans strategically and heat and ventilate at sunset to avoid condensation.
Among the fungicide choices, strobilurins such as Heritage and Compass alternated with Eagle, Terraguard or Strike is a strong program that conveniently guards against powdery mildew and gives some Botrytis suppression. Mancozeb-containing materials are effective but may leave high residue, so these should be used at early stages of production.
The symptoms of scab are very striking. The spots are light-colored, small, round, and blistered out from the leaf surface; often they run down a vein. There is usually a yellow halo around each spot. The fungus also infects stems, where it causes larger raised whitish oval “scabs”. Eventually these stem lesions turn brown, after the spores have matured. The most peculiar scab symptom of all is seen on plants that have stem infections, or else extremely heavily infected leaves. The shoots that have these symptoms will hyper-elongate, so that they stretch up several inches higher than the rest of the crop. This effect is due to the plant growth hormone produced by the invading fungus!
Although scab can cause alarm because it is unfamiliar—it is not a disease that occurs every year without fail (like Botrytis!)—it is actually very nicely controlled via fungicides and cultural adjustments. The trick is to notice that it is present in the crop, so that the diseased plants may be promptly rogued out and the neighboring plants treated for their protection.
Often it is the growing areas with the highest amounts of leaf wetness where scab disease symptoms appear. Long periods of leaf wetness are needed for infection. Adjusting cultural procedures so as to reduce the length of time the foliage sits wet is important: water early in the day, use fans strategically and heat and ventilate at sunset to avoid condensation.
Among the fungicide choices, strobilurins such as Heritage and Compass alternated with Eagle, Terraguard or Strike is a strong program that conveniently guards against powdery mildew and gives some Botrytis suppression. Mancozeb-containing materials are effective but may leave high residue, so these should be used at early stages of production.
The symptoms of scab are very striking. The spots are light-colored, small, round, and blistered out from the leaf surface; often they run down a vein. There is usually a yellow halo around each spot. The fungus also infects stems, where it causes larger raised whitish oval “scabs”. Eventually these stem lesions turn brown, after the spores have matured. The most peculiar scab symptom of all is seen on plants that have stem infections, or else extremely heavily infected leaves. The shoots that have these symptoms will hyper-elongate, so that they stretch up several inches higher than the rest of the crop. This effect is due to the plant growth hormone produced by the invading fungus!
Raised oval lesions form on stems as well.
Poinsettias with scab lesions on the stems will hyperelongate. Here the (normal height) plant at the right had only moderate leaf infection, while the one on the left had “scabs” on the stem as well. Photos: Maria Tobiasz Article extracted from "Scab on Poinsettias Again This Season" by Margery Daughtrey, Cornell University Dept. of Plant Pathology, LI Horticultural Research & Extension Center in the October 2005 edition of Northeast Greenhouse IPM notes.
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