Anybody know of a organic solution to black spot on roses? Any help would be greatly appreciated!
As these “Black spots” that you describe are a form of “Fungus” and you are looking for an Organic solution to this problem, perhaps I can suggest “Prayer” that is about your only hope.
A more helpful response, from someone who has nearly 100 roses, all grown organically, it to experiment with various sprays and growing conditions and companions: Garlic, planted around roses increases sulfur in the soil, but this takes several years to be effective. Water, a sharp spray in the morning will knock off infected leaves and take many of the spores with them, preventing the new foliage from becoming infected.
Do this early in the day so the foliage will not remain damp for a long time, which encourages black spot. Make sure the roses get adequate sun and air circulation and are staked if necessary to prevent the leaves from coming in contact with the soil. I have been experimenting with the use of WiltPruf to stop the spread of blackspot. It seals the leaf surface and inhibits the fungus’ ability to infect the leaves. Also, it keeps the plant from drying out and becoming stressed, making it generally stronger.
Once the leaves have blackspot, it can’t be „cured”, but you can get rid of the infected foliage and stop the fungus from being spread to new foliage. In the winter, you can try dormant oil to prevent the fungus from overwintering on the canes and infecting the leaves next year.
For fungus problems try using horticultural corn meal mixed into the soil. This by itself seems to be the best fungus fighter around. Also, Alliance makes a soil admendment with corn meal, wheat bran, and molasses. This works as a very mild yet powerful firtalizer and fungus control. I use it in all my bed preps at about 40 lbs per 1000 sq feet.