What is black spot disease?
Black spot is a disease in roses caused by the fungus Diplocarpon Rosae. It presents as black or brown spots on the leaves of roses. It can usually be tolerated by an otherwise healthy rose in a mild form, but left untreated it can spread. When the disease spreads and the spots become more prevalent, the leaves will begin to yellow and drop. The canes of the rose can also display yellowing and some spotting, but it most often is noticed on the leaves of the rose. Eventually the disease can cause the entire plant to lose it’s leaves, therefore losing it’s ability to photosynthesize.
One of the reasons I decided to write this blog post is because I couldn’t find any images that showed how the disease spread over time. I am located in zone 8a of Georgia, and it remains very hot and humid for the better part of our year. One factor that increases the chance of black spot is constant moisture, such as humidity. Since it is nearly impossible to keep my rose leaves dry with my level of humidity and at times, rain, it seems as if I am at war with my very climate.
Now that you have a brief description of what black spot looks like, I would like to share images of the disease from mild to severe.
Treating black spot disease
When I was researching treatments, I wanted to avoid using strong chemicals on my roses for fear of burning them. I tried several mixtures including diluted milk, a baking soda solution, and a white vinegar / oil concoction. None of them were successful for me. Next, I purchased a 3-in-1 Neem Oil product that was touted to be a combination fungicide / miticide / insecticide. Since Neem Oil is a natural product I was willing to give it a go. I was very surprised with the results that I had with the Neem Oil spray and continue to use it successfully on my roses when I have an outbreak. Just a note to not spray your roses in the morning or during the day, because it can cause burning on the leaves in the same way that watering during the day can cause. I spray my roses every other evening during our rainy season until I notice all of the black spots are gone from the infected plant.
I will link the spray I have used on my roses and would love to hear if it works as well for you. In the future, when purchasing roses look for more disease resistant strains will also help to minimize the spread of black spot. Good luck and happy gardening!