PM on seedling inside under lights

I’m trying to save one of my seedlings after it lost most of its roots somehow. I brought it inside and am growing it under lights now. It has responded well and has put out good growth, but it now it’s getting PM on the leaves. What should I do? What is the best way to treat this?



Hi Paul,

PM doesn’t have to be treated, but is promoted by high daytime and cool night time temps. Did it get PM outside? Was it a mature seedling? Depending on how many other good traits it has, if it is badly infected, you may want to weigh out the good vs. the bad traits.

I am only keeping a rare seedling that gets PM - and only if it has some unique trait that I want to move forward with.

Jim Sproul

Hi Jim,

Right now it is in my basement under grow lights, so the temp and humidity should be pretty constant. I don’t usually get disease on my seedlings inside other than damping off. But then this is the first time I’ve had seedlings inside in November though.

It is one of this years seedlings. It was hit by a late frost last spring and it took some time to recover, so it isn’t very big. It had been very healthy, so I was surprised when the leaves just dried up and dropped. When I dug it up I saw that most of the roots were gone, I realized that I might be able to save it. Before it dropped its leaves I was excited about it because it was healthy with an unusual color that had good substance and form.

Though it was healthy outside, I culled some of it’s siblings because they got PM pretty bad. So I shouldn’t be too surprised that it has developed some also. I have read that some plants can be more prone to PM when grown in a greenhouse compared to when grown outside and I thought that might be the case here also.

So I guess your saying is that I shouldn’t treat the PM as it may not get that bad and if it does, I’ll have a decision to make.



Hi Paul,

What I meeant by not having to treat it, is that PM is not deadly. To clean it up if you want, you might consider taking it outside to spray it with a fungicide and bring it back into the house after the spray dries.

I think that it is true that indoor growth is more delicate and prone to PM. Certainly if this seedling has some of the other qualities that you are looking for, especially if it is blackspot resistant, you will want to save it.

Good luck with it!

Jim Sproul

Thanks Jim,

I know that PM is not deadly, but it can be quite disfiguring and I just wanted to nip it in the bud before it got too bad. I have a few other plants inside also and I just don’t want it to spread them as well. That’s good a point about taking it outside to spray it, it’s not that cold yet.

Though it may not be a plant that could be released to the public, it does have some qualities that I would like to evaluate more and maybe expand on.


Hi, Paul G.,

I had that happen with a seedling that sprouted in September; it got powdery mildew on the cotyledons! (And therefore I suspect this rose is a moss.) I sprayed it with Safer, and brought it into the greenhouse where it’s now under lights. One application did the trick, the little thing has many new leaves and is free of mildew.

Thanks Fara,

I sprayed some seedlings years ago when I had a damping off problem. They did not like at all, though they didn’t die, the leaves became all deformed. I don’t recall what I used then. So maybe I better use something like Safer or Bayer Advanced that is known to be less toxic.


I haven’t totally eliminated pesticides/fungicides from my roses yet, but I do check out the few I use for their toxicity before using them. As a former user of Bayer Advanced, I noticed that the bees would do all kinds of crazy stuff when gathering pollen from roses treated with Bayer-I attributed it to a “catnip” convulsion, like a cat with to much of a good thing. But then I noticed how many bees were ending up dead on the pavement, in the birdbath, and just plain disappearing;where I used to have many hundreds, I suddenly had days pass without any bees. (And I realize that this was not just from my roses-I live in a suburban area with lots of flowers, fruits, and bee attractants, along with neighbors who use Bayer on everything-esp. Bayer Advanced All in One for roses) And then I looked into Bayer, and they do have a good PR machine. Reminds me of the current political campaign. Check for some of the facts yourself-there are hundreds of studies that dispute Bayers’ bias. I cite a few links.

Greenpeace Publishes Pesticides Industry Ranking Bayer Pesticides Are Most Damaging for Humans and The Environment

Germany Bans Eight Pesticides Linked to Honeybee Population Collapse; Clothianidin Chemical Found Contaminating Dead Bees - The German government has provisionally banned a family of pesticides conclusively linked to the massive dieoff of honeybees in a southern state.


Not all Bayer products are the same. Some Bayer products don’t contain insecticides. I use Bayer Advanced Disease Control for Roses, Flowers & Shrubs. It is fungicide only. I have lots of bees and almost every other kind of bug.

The All-in-One (which lots of people pick up by mistake, or by the prompting of uninformed salespersons) has insecticide and fertilizer in it too, and I’d encourage you to leave it on the shelf.



If you want to control PM and don’t want to use a pesticide (not too many are for use in the house) I’d like to suggest spraying your seedling with 1:10 solution of Wilt-Pruf. This anti-dessicant will stop and control mildew.

You might also install an oscillating fan over your seedlings under lights. The air movement seems to prevent PM and actually ‘strengthens’ the stems due to the movement of the fan breeze.

Thanks Meg,

Those are good ideas. I think I will put up a fan and look into Wilt-Pruf as an alternitive to the fungacides. I tried some fungacide that I had around the house, but it’s to early to tell if it worked.