MORE URGENT GARDEN QUESTIONS: In the July edition of Ken Druse’s and my monthly Q&A radio podcast, we tackled listener questions about powdery mildew prevention and aftercare, and what to do when an abundance of roly-poly or sowbugs and pillbugs has descend on the garden. Also: Should you use copper-based fungicides against tomato blight—and what to do after an infestation by the garlic bloat nematode?

In Part 1 (a transcript of which is at this link) we talked with a caller curious about the wonderful tree called Stewartia and how to make it happy—plus Ken recommended other garden-sized, multi-season trees to consider adding to your landscape, including dogwoods, redbuds, and tree lilacs.

Ken, of Ken Druse dot com, is a longtime garden writer, author and photographer and all-around great gardener—and great friend. If you have a question for a future show, you can submit it in the comments on either of our websites, or use the contact form to send us an email from either site, or ask us on my Facebook page.

Read along as you listen to the July 10, 2017 edition of my public-radio show and podcast using the player below (or at this link). This is Part 2 of the two-part show, beginning at 24:48 in the audio.

And a small apology: The sound, especially in Part 1, is a little uneven; we had an electrical brownout in the area while taping and lost our master audio file. The backup that survived this unique power event was not ideal, but the transcript is thorough.

part 2 of the july q&a with ken druse

Image from Missouri Botanical Garden

tackling powdery mildew

Q. I have a question I suspect others are having at this moment, from Zoe on email via the contact form on my website:

“Help! Several of my peonies have powdery mildew. From what I’ve read, it’s best to prevent early on, but now that the blooms have passed what, if any, action should I take to clean/remove the mildew.”

Did you know that there are like 11,000 species of powdery mildew organisms on ornamental plants? [Above, mildew on peony foliage, from Missouri Botanical Garden.]

Ken. I don’t doubt it for a minute—there are like 12 growing on the sponge in the kitchen.

Q. So the basic thing is when you get warm days and cool nights, it can be good conditions for it, and the spores exist—that’s what happened to Zoe. My understanding is that once it happens you don’t get rid of it, right?

Ken. It doesn’t seem to ever really be…

Q. It doesn’t kill it.

Ken. It’s not terminal, it’s just unsightly. It’s very unsightly, and the lilacs always seem to get it at the end of the summer, but it doesn’t seem to kill them.

Q. And really, it’s fungal—and really when she said peonies…

Ken. Botrytis…

Q. Yes, so you like to check because peonies get other fungal diseases, so you want to check. It’s great to go to Missouri Botanical Garden website, or Cornell—or if you live in a different region, pick a different botanical garden website. Look at some pictures of the different fungal diseases of the plant, so you can be sure. I think she is sure; she knows what it is.

So really with these fungal diseases, prevention is the thing—but those fungicides that were used for prevention, I don’t want to be spraying that stuff.

Ken. I’d like to go back in time; I’d like to be 26. But that’s another story.

Q. OK. [Laughter.]

Ken. You said prevention, and I would say especially with peonies, if you see any kind of disease on them, in the fall when things are quieting down and everything’s turning brown, that’s one plant I would cut the foliage off and discard; put it in the garbage. Don’t compost it.

Q. I agree; anything with a mildew situation or let alone botrytis—the fungal diseases. A really, really good cleanup in fall, including raking up under the plants. If it’s really disfigured or discolored—besmirched! [laughter]—you can even cut off some of the worst so that you can limit the number of spores that are flying around, but you don’t want to defoliate the plant entirely early in the season. That’s a judgment call, I think.

Since roses get fungal diseases, too, rosarians have looked for what’s natural, safe antifungal preventive thing instead of [chemical] fungicides. Isn’t there a baking soda recipe?

Ken. I used to use that, something like a tablespoon to a gallon of water, and then you need something for a spreader-sticker, a surfactant, like dish soap or better would be some kind of sun oil, some kind of natural oil spray so it spreads over the leaves. But a lot of people, especially rose people, really had not as much success as Napalm, but a lot of success with baking soda—and of course it’s perfectly safe.

Q. I looked up Cornell’s recipe, because I remember it was like the late 80s or 90s when they did some testing. It was like you said, but they used a little extra baking soda—like 4 teaspoons instead of a tablespoon, and a gallon of water, and they put a couple of teaspoons of Sunspray or one of the other ultrafine, year-round horticultural oils (again, not toxic). And they put it in a no-clog kind of hose-end sprayer, and then they sprayed them prophylactically—not once they had an outbreak—every three to fours days, and had tremendous results.

[Vintage-2001 pdf on baking soda recipes for fungicidal use, from National Sustainable Agriculture Information Service.]

Armadillidium vulgare pillbug from Wikipedia

pillbugs and sowbugs

Q. I think we have a caller on the line named Lynda. Where are you calling from?

Lynda. I’m calling from Lilburn, Georgia, which is just outside Atlanta—northeast of Atlanta. It’s kind of hot and steamy here, as opposed to what you guys have.

Q. We actually are having a break from the humidity, which we are very thankful for, but I guess you are not.

Lynda. No, full-tilt. We were in Maine and Canada recently and enjoyed it, and came back and walked into a wall of humidity that hasn’t left since we got home.

Q. My goodness. So what’s your question?

Lynda. Well part of it is because of all the rain we’ve had, but I seem to be overrun with the little pillbugs and sowbugs—both kinds. I do kind of know…