major black spot infestation in hybrid tea roses

Question

Hello. My roses got black spot like crazy this season. Is there anything I can do now before the end of the season (probably about 6 weeks until first freeze)? I even transplanted a couple bushes to try to get them more air to help deal with the fungus. Thank you.

Bryce Anderson
Omaha, Nebraska

Answer 1

Some rosebushes seem to be black spot magnets and will be attacked at the drop of a hat regardless of where they are planted or the air circulation provided. When under a severe black spot attack, I have found only one product that flat stops black spot in its tracks and helps me gain control of the situation. It is called Mancozeb. It is available for purchase on Amazon.com or at a website called Rosemania.com. Under severe attack you will likely need to spray the rosebushes down with this product 3 to 4 times at 5 to 7 day intervals. Mancozeb fungicide will leave a yellowish powdery looking residue on the foliage, this is part of how it works. If the black spot fungus is killed, the new foliage coming on should be free of the fungus. The old black spot damage will not go away and will be on the foliage effected until they eventually drop off the bush. The worst rosebush I ever had for getting black spot was named Angel Face. Love that rosebush and the fragrance of her blooms as Heavenly, but she had to be kept sprayed or she would get black spot and totally defoliate! Thus I do not grow her in my rose beds anymore. Here is a link to an article I wrote on this subject for you as well: https://www.gardeningknowhow.com/ornamental/flowers/roses/black-spot-roses.htm