I think the soil is too acidic? The upcurled leaves and the PM are a sign for that.

I have not had any fungal problems with my roses since 2002 when I began using ordinary corn meal to feed them. Before that they were covered with black spot and powdery mildew. Also keep the base mulched so that when it rains, no soil splashes up onto the stems of the plant. I have also had no more problems with aphids since 2002. Coincidence? I don't think so. Every month I drop a heaping handful of cornmeal down from the top of the plant for every foot height of plant.

in my MI.. when i grew roses.. i had to spray them every 6 weeks.. starting easily in the season... this was back pre WWW... so i dint have any info on options..

either start a spray regimen... or find plants that are more resistant to the problem...

also.. NEVER wet the leaves int eh evening.. and if possible.. dont let the lawn irrigation wet them at night...

and if possible.. increase air movement... thru judicious pruning of other plants ..

standing in dark dank still air.. is what mildew is all about...

ken

Powdery mildew has nothing to do with soil pH. The pH may have an impact on other growing issues if out of whack but PM is primarily weather related although also encouraged by lack of air circulation, over crowding and excessive shade.

dchall: as you drop cornmeal down from the top of the plant, are you trying to get cornmeal to stick to the foliage to exert anti-PM effect, or is it just a convenient way to get the cornmeal to the base of the plant? You did mention ”feed”.

I sometimes try to throw the cornmeal under that plant but it all lands in one clump. Organic fertilizer hates being in a clump, so when you drop it down through the middle of the plant there is a Plinko effect which randomizes the droppage through the leaves.

Cornmeal is one of the ingredients in many organic fertilizers. When the beneficial microbes in the soil decompose it, in about 3 weeks the end result is plant food. That is why organic fertilizer is said to be slow release. Actually it is slow decomp followed by very fast uptake by the plants.

What cornmeal do you use?

I use whatever they have at the feed store. Ordinary whole ground corn meal. NOT corn gluten meal.