Question of the Week – Number 2 May 20, 2021 – Black Spot of Roses
“My roses’ leaves are developing black spots and falling off. What is wrong with them? How can I stop it?
This fungus dates back to the beginnings of rose growing. It’s far more serious in the warm, humid weather of spring and fall. It abates somewhat in summer’s hot, dry weather.
Some varieties of roses are far more susceptible to black spot than others. From that beginning, my friend Dr. Steve George of the Texas AgriLife Extension of Texas A&M began an exhaustive comparative study probably 30 years ago in which hundreds of rose varieties were grown and evaluated side by side at a large number of test sites in both Texas and across America.
As it became obvious that some of the varieties were far more resistant to black spot than others the tests were refined and the best of the best were identified as EarthKind® Roses. Click to read more at the Texas A&M website.
If you have a plant that is, unfortunately, not one of the EarthKind® Rose selections, apply an approved fungicide weekly in spring and fall. Plant your roses in raised beds in areas with good air circulation.
Note: As you’re growing roses, keep your eyes open at the same time for the serious rose rosette virus. It is a fatal disease for which we have no effective preventive technique, nor do we have a control once a plant is infected. See the information I have archived at my website.