Has anyone used either milk or cornmeal/water spray successfully for blackspot on roses?
Milk and cornmeal sprays for blackspot
I've tried cornmeal sprinkled around the roses and had some luck with that. I used a copper spray on the neighbors roses and I think that it helped. Not sure as I was gone for a week - but I noticed that they looked much better when I was pruning them yesterday.
I have had great success in doing the following:
1 week spray with the following mixture: 1/2 tablespoon of apple cider vinegar, 1/2 tablespoon of pinesol and 1 quart of water.
following week spray with the following mixture: 1/2 tablespoon of baking soda, /2 tablespoon of pinesol and 1 quart of water.
I have been neglectful and did not maintain weekly spraying ... hoping the problem was gone for the season ....WRONG, WRONG, WRONG
Yesterday I noticed a black spot on a rose leaf. I apologized to the bush and later sprayed with the apple cider vinegar mixture. Next week I will use the baking soda mixture.
I do not know why but you should alternate the mixtures you use for spraying.
Neem oil is the best thing for black spot on roses but you have to start spraying early and maintain a regular spray schedule.
Just remembered one more remedy that works (sorry, I no longer grow roses, no time). Take leaves from tomato plants, about a cup full. Mix with one quart water in a blender, blend until really chopped up like slush. Strain to remove pulp, spray once a week. Same as neem, start early and maintain a regular schedule.
I'm having really good luck this year with a copper soap. I started spraying BEFORE I saw any mildew or black spot and continue every two weeks.
I like copper soap, it works well on PM and doesn't burn the leaves of tender plants.