Organic Control of Black Spot on Roses

“I would alike a solid reccomendation for preventing diseases and
especially black spot on roses.  I have four of your roses and they are
doing great but I do know that disease and ‘spot’ will show up especially in
florida.  Your help will be greatly appreciated.  Thanks! ~J.D.”

Thanks for the email regarding black spot on roses.  There are several
organic ways to control black spot. Most of them rely on regular monitoring
and upkeep. None of them are difficult, and can be accomplished while you’re
admiring your roses.

–Plant roses in full sun. If you give your roses a spot where they receive
a full six to eight hours of sun per day, you’ll not only have plants that
grow more robustly, but also plants that are more able to resist black spot.
Black spot loves moisture, and, in shade, water evaporates much more slowly.
In full sun, evaporation happens more quickly, which not only helps prevent
black spot, but other fungal diseases as well.

–Plant roses in an area with good air circulation. This accomplishes the
same thing as planting in full sun: moisture evaporates more quickly. In
addition, with plenty of air circulation, hopefully breezes will blow any
newly-germinated black spot spores away from your roses. In an area with
poor air circulation, the spores have nowhere to go but back onto your plant
and the surrounding soil.

–Water correctly. Try to avoid overhead irrigation, which wets the foliage.
It’s more efficient to water at ground level anyway; you lose less water to
evaporation. Also, avoid watering late in the day. Water evaporates much
slower in cooler evening and nighttime temperatures.

–Remove leaves that show signs of infection. As soon as you see black spot
on your rose foliage, remove any infected leaves. Throw these leaves away.
Don’t put them in your compost pile. If you check your roses regularly, and
remove infected foliage immediately, you’ll have a good chance of keeping
black spot under control and keep it from infecting other parts of the

–Keep a clean garden. Pick up and throw away any fallen rose foliage
regularly. Especially in late winter, rake up the area around your roses,
dispose of any debris, and give the entire area a good three inch deep layer
of mulch. If you do this before new foliage begins to emerge, it’s fairly
unlikely that you’ll have any major issues with black spot.

–Choose resistant cultivars. If you’ve had persistent problems with black
spot in the past prior to your current four roses, be sure to make sure that
any new roses you add to your garden are resistant. Your local cooperative
extension service will be able to provide you with suggestions.

By following these steps, your roses should be healthy and beautiful for
many, many years to come.




© Mertie Mae Botanics LLC and Horticulture Talk!, 2011. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Mertie Mae Botanics LLC and Horticulture Talk! with appropriate and specific direction to the original content.


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