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Rose Pests and Problems
by ChuchWelch

 

Roses are easy to grow if given the proper conditions.  Adequate sunlight (5-6 hours minimum), water (about an inch a week on average) and fertilizer (roses are gluttons and love to be fed).  Roses are also like most any other garden plants in that they are susceptible to a number of diseases, insect pests and other problems.  It is up to the gardener to decide what level of  damage and maintenance, or lack of,  they are willing to live with.  The hard core exhibitor is striving for the perfect bloom and immaculate foliage, and will do whatever it takes to achieve that goal.  Then there is the "survival of the fittest" type gardener.  This type gardener digs a hole, plops a rose bush in, fills the hole,  and gives little, if any, water or fertilizer through out the year.  Most rose gardeners fall some where in between the two extremes. 

Diseases

The most common disease problems in the Atlanta area are fungal diseases such as Blackspot, Powdery Mildew, Downy Mildew and Bothyris .  Blackspot is the most common disease and causes dark circular spots with irregular margins, mainly on the upper surfaces of the leaves.  The spots enlarge until the leaf turns yellow and drops from the plant.  Blackspot loves the humid conditions found in the Georgia and the Southeast and can occur at any time in the growing season. Uncontrolled blackspot can rapidly defoliate a rose bush and spread throughout a rosebed.  There is no cure for blackspot only prevention.  One of the best ways to control blackspot and other fungal diseases is the regular application of fungicides.  The ARS website has an article on blackspot titled What is Blackspot?.   Other ARS articles on Powder Mildew and Downy Mildew can be found at the Diseases in Roses page on the ARS website.

Two of the more serious disease problems are Rose Rosette and Rose Mosaic . While Rose Rosette hasn't been reported in Georgia, confirmed cases have been found in western and middle Tennessee, with possible cases in the Huntsville, Alabama area.  It is thought to be caused by a virus and spread by a specific type of mite.  Good articles on Rose Rosette can be found at:

Rose Mosaic is also thought to be caused by a virus that, unlike Rose Rosette, is not fatal to roses.  However it has been shown to reduce the vigor and flower production of most infected plants.  An excellent article on Rose Mosaic by Dr. Malcom Manners, of Florida Southern College, can be found on the ARS website at Rose Mosaic Virus Disease.

Insects

There are a multitude of insects that feast on roses and almost as many solutions for eliminating them.  Fortunately, most of the bad bugs have a good bug counterpart or predator.  The problem is that you first must have the bad bugs before the good ones show up and by then the damage is done.

Some of the more common bad bugs are aphids, thrips, caterpillars, grasshoppers, spider mites,  and the dreaded Japanese beetle.  The most common good bugs are Lady bugs, bees and wasps, praying mantis, and the one that I personally hate but co-exist with in the rose bed - the spiders.

All of the bug problems can be treated by various insecticide sprays with varying degrees of success.  The thing to remember is that when you use insecticides you are also killing the good bugs, which in the long run may make your problem worse.   By using Integrated Pest Management (IPM) you may be able to keep your bug problems under control.  A good place for more information on IPM is at www.gaipm.org/turf/index.html which is published by the UGA Dept. of Entomology.

If you do choose to use sprays, either fungicides, insecticides or combinations, always read the label carefully and follow mixing directions exactly.  This stuff is poison!!!  

More information on insects and insect control can be found at: http://www.jps.net/rosebug/
http://www.nysaes.cornell.edu/ent/biocontrol/predators/predtoc.html

Pesticide Safety information can be found at: http://ace.orst.edu/info/extoxnet/pips/ghindex.html