White Mold On My Miniature Rose Leaves

[Flowers]

Okay, so a couple days ago I noticed a leaf with white mold on it on my "Parade Roses". Now, several leaves have this mold on them. I removed these leaves in hope to avoid the mold spreading.

It is sitting on a window sill with several other plants. I water it every other day to keep the soil moist and mist it occassionally (once or twice a week) for humidity. Last week, I noticed some aphids on the plant and picked them off, but I don't see any now.

What is this? Thanks a bunch, as always!

[applestar]

It's probably powdery mildew. You could start by trying a spray of 1 part milk and 4 parts filtered/U chlorinated water. Put the plant in the sink or outside and spray thoroughly top and underside of the leaves, stems, growing tips, all over unti, dripping. Keep it out of direct sun until the droplets dry. There are various theories about why this works (or doesn't work). We discussed it here and I have a post/thread with a bunch of reference links. Suffice it to say it's a non-toxic benign method that is an excellent preventative and should work on a minor initial infestation.

I would repeat in a week.

If this doesn't work, you could go for somewhat more stronger remedy like baking soda solution or hydrogen peroxide solution which will kill the fungus.

[imafan26]

I prefer copper sulfate for mildew on roses, but the the milk and other things should also work. You want to make sure the plant has good air circulation and to avoid the leaves staying wet. If the plant is outside where it will get rained on a lot, fungicides need to be applied weekly as long as the air is humid. Outside you can use something like systemic rose care which will control mildew and black spot for up to six weeks. Make sure the roses do not have blooms on them at this time to protect the bees.

As a preventive when I know rain is coming, I spray my plants with either the copper sulfate or I spray with a horticultural oil (not neem). The oil makes the leaves slicker and more water repellent so they water does not stay on the leaf as long. If oil is used then it cannot be used within two weeks of using sulfur. Oil and sulfur combined will burn the plant, so chose one or the other but not both. If it is going to rain for several days, I prefer to use the oil because sulfur will be washed off the plant by the rain but the oil is not. When the rain stops, that is when it gets humid as the moisture steams off and that is usually when fungal problems appear.

If the plant is inside, then try to keep the leaves dry and don't over water the plant. Have a fan gently creating a breeze to help keep the leaves drier.

If the rose can handle it cut off heavily infested leaves and dispose of them in a sealed bag. That will leave fewer spores in the air.

Feed the rose and make sure it is in good soil and not pot bound. A healthy plant is more resilient. Roses with glossy leaves are less susceptible than roses with matte leaves.

[Flowers]

I'm still having this problem after trying the milk solution twice, one week apart. The plant is inside, so rain isn't a concern and I take good care not to get any water on the leaves. I haven't been misting it either. I did notice that several of the leaves were overlapping and crowding each other, so I have been taking care to prune out the overcrowded leaves to increase circulation. I have also repotted since this post to ensure that it is healthy.

Any suggestions? What ratio would you recomend for baking soda or hydrogen peroxide solutions?

[imafan26]

If there are only a few leaves involved, pick them off.

You can try alcohol or hydrogen peroxide straight out of the bottle. Hydrogen peroxide does have anti- fungal properties. Alcohol promotes drying of the leaves. I use alcohol for bug control too.

I usually use copper sulfate or sulfur dust for powdery mildew.

Fungal disease is hard to stop once it takes hold, especially when the fungal filaments dig into to the leaf. If your plant is no where near pets or people (kids) and it is in the house, you can use systemic rose care. It will treat the fungal infection internally and lasts about 6 weeks. I would still pick off any of the infested leaves just to keep the spores from spreading.