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Powdery Mildew on Basil

Posted by shadygarden_co z5 Denver (My Page) on
Fri, Jul 9, 10 at 20:50

I heard today on NPR that powdery mildew was appearing on basil plants and was glad to figure out what was wrong with my basil. The leaves appear yellow and if you look at the underside, you see very fine gray or almost black powder.

I am just wondering if anyone else in the Denver area has this problem, and, if so, what you are doing (if anything) about it. I Googled it and apparently it isn't toxic to humans and you should just destroy the affected leaves.

I'd love to know if someone else has it.


Follow-Up Postings:

RE: Powdery Mildew on Basil

I don't have it but each year I get white powdery mildew on my...weeds! If I don't pull them or cut them, they look like they've been dusted in baby powder and then it gets on the violas. So, I pull, chop, pull and pull.

But, this is the first year I'm trying basil up here so hopefully it won't happen. We are having a pretty wet summer so far...

Can you remove the infected parts then bring the plants inside at night?


RE: Powdery Mildew on Basil

Marlene, I was at first inclined to say, "Don't you mean fusarium wilt."

I mean, that's the big disease problem with my basil. I've decided to NOT grow some of the Italian varieties next year that are so vulnerable to it. There are newer types that have resistance.

Then I read a little about fusarium wilt. Here's what North Carolina State says about it, "Fusarium oxysporum f. sp. basilicum was first discovered in the U.S. in 1991 and identified in N.C. in 1992." Wow!!

So, I began growing basil about the same time it showed up in the US! I just thought it had always been around . . .

Okay, if fusarium wilt has only been here for 20 years, I suppose that we are about due for something new. Powdery mildew, you say?

I never got the milk out to the garden to see how it would work sprayed on those developing pea vines (and their "developing" powdery mildew). Maybe I'll get around to spraying the summer squash with it. And, maybe it would help with basil . . .


RE: Powdery Mildew on Basil

  • Posted by skybird z5, Denver, CO (My Page) on
    Sat, Jul 10, 10 at 16:20

Basil is one thing Ive never had powdery mildew on. Really glad for that, since its an eatin type thing! Several years ago I did get it really bad on the peas, but that was towards the end, and since I wasnt eating the pods, I just washed them off and ate the peas anyway! Havent seen it on the peas again since thenand I think that was one of the years I wasnt around here to water regularly, so they were way stressed that year.

Jennifer, lots of weeds, and bindweed in particular, can get mildew really, really badespecially when theyre/its not getting water and is stressed, based on my experience at my last housewhere there was a whole (unseen from the house) "field" of it that I mostly ignored since it was a rental house! Maybe you should do a better job of watering your weeds! LOL! I do recommend you keep cutting and pulling themjust to keep it from reaching critical mass! Ka-boom! There goes Nederland!

Most of my little omnipresent purple violas are starting to get it by the time they reach middle age, and as soon as I see it, I just pull them out and toss them in the trash! There are ALWAYS more to replace them!

I havent had a serious problem with it on any of my perennials since I got rid of my Scabiosa a few years back. From my observations, I still stand by my theory that the more stressed a plant is, the more likely it is to get mildewand various other maladies. So I try to keep most things well watered, and to keep dead, dying, and damaged leaves cleaned off, and get things cut down pretty promptly when they finish blooming.

But Im going to resurrect a thread from 07 where we were discussing mildew and some of the possible options for dealing with it!

I never got back for a final report at the end of that thread, so here it is!

The baking soda I was experimenting with didnt seem to work any better or any worse than the commercial topical fungicides I had tried in the past. It had to be sprayed over and over and over, and then there was a white residue from the baking soda, which didnt look much better than the mildew, but at least didnt seem to damage the foliage! I gave up on the baking soda the same as I had given up on the commercial stuff. But at least the baking soda was way cheaper than the store-bought stuff!

Then I tried the milk solution Digit brought up above. That pretty much had the same result as the baking soda and everything else I had tried. It had to be applied over and over and over, and while it seemed to help somewhat when I kept applying it, as soon as I stoppedMILDEW! Gave up on that too! My final solution for the Scabiosa that was NEVER without mildew, no matter how young the leaves were and no matter how well it was taken care of, was to dig it up and throw it in the trash! No more mildew on the Scabiosa!

With basil, I guess Id recommend cutting it WAY back, and trying the baking soda or milk spray just to keep it going long enough to get some useable basil. Keeping it well watered, and washing it off thoroughly with the hose when youre watering it may help too, and definitely wont hurt. Im still not convinced that wet foliage is the main promoter of mildew, but just to be sure, Id recommend the watering and washing early enough that the foliage is well dried before dark! (Im not convinced of the wet foliage theory, because several times when I was back in HIGH HUMIDITY, wet all the time, Illinois, roses and other things I expected to see COVERED with mildew, had NONE! In my head, that really messed with the theory that too much moisture on the foliage was the cause of mildew!)

So heres the link to the old thread which has some good info and some possible things to try.

Good luck with the basil,

Here is a link that might be useful: Shoveling Sand against the Tide? - 07.01.07

RE: Powdery Mildew on Basil

  • Posted by jnfr z5b CO (My Page) on
    Sat, Jul 10, 10 at 16:40

I've never had powdery mildew on basil either, knock on wood. It does come in on the bindweed, and usually my squashes succumb to it at the end of the season (by which time I've usually had enough squash anyway!)

RE: Powdery Mildew on Basil

I remember that thread, Skybird! Still miss Cnetter . . .

Immunex fungicide is back in the sprayer again this year.


RE: Powdery Mildew on Basil

Shouldn't have PM out here on basil. If you do, you are watering Waaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaay too much.


RE: Powdery Mildew on Basil

Yeah, I've never seen PM on basil before. I'm wondering what part of the country the NPR show was referring to?


RE: Powdery Mildew on Basil

Mid-Atlantic states, following on with the blight problems they are having again.


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