It’s Coming for Our Basil!

News of a new blight, which I had not heard about until people started talking about it on yesterday’s pesto threads:

A potentially fatal fungal disease called downy mildew has been attacking basil plants in New York, New Jersey, Ohio and Florida. Gardeners are worried that it could spread farther throughout the summer, turning delicate green basil leaves an ugly shade of brown, yellow or gray…
So-called basil blight is similar to late blight in tomatoes or downy mildew in cucumbers, squash and melons. McGrath says these are considered “community diseases” because they move easily. “If you have it in your garden, you can affect other gardeners and farmers because the pathogen can jump onto their crops and plants,” she says…
The sign of the blight, McGrath says, is the top of the leaf will start yellowing. But to really know the state of the plant, you have to flip the leaves over and look on the undersides.
“You’ll see a grayish, almost purplish dusty growth on the underside, sometimes turning to almost black — and that is all of the pathogen spores. And there are incredible production of them on the underside of the leaves,” she says. “The wind will pick those up and blow them off and the disease just keeps multiplying like crazy.”
McGrath says that if you see the blight, you could get rid of the leaves, but if you remove one, you’ll probably knock around the spores and they could get on other parts of the plant. She suggests making pesto on the spot with the healthy leaves when you see the first signs of blight.

This would be the year I decided to grow more than two basil plants. I’m planning to spend some time this afternoon spraying a product called Serenade on my plants. Don’t know if it will help with the basil blight, but it’s supposed to be a broad-spectrum fungicide, and I already planned to try it on the tomatoes, roses, and lilacs.

33 replies
  1. 1
    frankdawg says:

    Just heard about it on NPR a couple nights ago – another absolutely useless story with an ‘expert’ that illuminated nothing & provided no real information about the condition, what causes it, how to stop it.

    She did suggest that making pesto was a really good idea.

    “Hey! The Titanic just hit an iceberg!”
    NPR ‘expert’
    “Well this is a bad thing and the ship is taking on some water in some places. You should try swimming now.”

    & I am supposed to send money to support this level of ‘news’?

  2. 2
    Tom Betz says:

    Try a spray of one part full cream milk to 5 parts water, add a table spoon of bicarbonate of soda, and spray the leaves when not too hot in the morning or evening. Much less toxic than the commercial preparations.

  3. 3
    frankdawg says:

    @Tom Betz:

    Have you tried that on this blight & does it work?

    I’m think of moving some of mine indoors to try and protect it.

  4. 4
    Violet says:

    I’ve sprayed the baking soda and water mixture on my crepe myrtles. It killed off the powdery mildew pretty well. I didn’t do a good job of covering the leaves, but on what I managed to cover it killed off the mildew effectively.

  5. 5
    4tehlulz says:

    This is Obama’s Katrina.

  6. 6
    Tom Hilton says:

    And just so there are no misunderstandings downthread (it’s a really poorly worded story), it’s ‘potentially fatal’ to the plants, not to humans.

  7. 7
    ricky says:

    This is the worst news I have heard since learning Tori Spelling tried to dial up her dad on Psychic Friends and got that damn Farrah Fawcett instead. Not that I didn’t like Farrah but she did impose her death on Michael Jackson’s.

  8. 8
    mr. whipple says:

    Great, another disease to deal with this year.

  9. 9
    Li says:

    Plant pathologist here; serenade should work well against Oomycete diseases such as downy mildew. But, be sure that you are doing prophylactic sprayings every three or four days if downy is in your area, because it’s much more effective as a prophylactic than as a treatment (this is true of most Oomycete diseases actually). If you find a plant with the distinctive dry purplish grey spore mass under the leaves, rouge it out and burn it or bury it. I would suggest using a plastic grocery bag to cover the plant before cutting it off at the base, to prevent the light spores from being spread around. Or you could pesto it, I suppose.

    This is nothing new, it’s just been a cool moist spring and downy loves that. Greenhouse grown plants are immune if you are watering at the base, because the disease basically -requires- leaves to be wet for hours at a time.

  10. 10
    Li says:

    Oh, and bicarbonate of soda with either horticultural oil, sesame oil, or milk (there needs to be some fat to carry it) seems to work quite well too, but -only- as a prophylactic. It damages spores, but does nothing for established infections.

    Good luck!

  11. 11
    Tom Betz says:

    @Violet: The butterfat in the cream is in the mix I posted above so it sticks to the leaves better and spreads on them more evenly – it acts as a surfactant – giving the bicarb more of an opportunity to do its job.

    And no, I haven’t used it (no garden this year for a number of reasons), but people I trust have.

  12. 12
    Joel says:

    So if John Cleese’s herb garden gets hit by blight, does that mean he’s growing faulty basil?

  13. 13
    Gus says:

    @Joel: Groan (but smiling). I hope that doesn’t make it to my neck of the woods. I had blossom end rot on my San Marzanos last year. That sucked, but it was actually my own fault.

  14. 14
    SiubhanDuinne says:

    @Joel: Oh GROAN.

    @Tom Hilton: I fear I was the one responsible for the initial misinterpretation on yesterday’s thread. Thanks for giving me a bit of an out by saying it’s a really poorly-worded story.

  15. 15
    jeffreyw says:

    @Violet: Try adding a bit of dish detergent to the mix. Makes your potion “wetter”. Doesn’t take much. I mixed 15 gallons of a cattail herbicide once using maybe one ounce of Dawn, worked like a champ.

  16. 16
    QuaintIrene says:

    Try a spray of one part full cream milk to 5 parts water, add a table spoon of bicarbonate of soda, and spray the leaves when no

    I’ve tried spraying that concoction against powdery mildew on my squash plants and zinnias, two plants very prone to it.
    And it actually works! You have to wet the leaves pretty thoroughly and reapply after rainfall. But it’s a low-cost, organic way to beat it.
    And I even used skim milk.

    Agree that this article is useless. Exactly why is this mildew attacking basil plants this year? Is it a different variety? Like last years tomato blight, is it spread from commercially bought plants at Big Box stores?


  17. 17
    Violet says:

    @Tom Betz:
    That’s an interesting suggestion, using cream for the butterfat to hold it on the leaves. I’ve used dishwashing liquid and something hot like cayenne to deter something (I can’t remember what not) from eating my plants. The dishwashing liquid was supposed to hold the cayenne on the plants.

  18. 18
    frankdawg says:


    And we have a winner :) Thanks.

    Thank you very much! YOU should have been on NPR the other day. As noted above about the on-line version the audio version was poorly worded & pretty much useless.

    I’m sorry but I have to add:
    ha-hee-hee, he said prophylactic
    Its the inner Bevis

  19. 19
    Tom Hilton says:

    @SiubhanDuinne: it really is poorly worded, and I don’t blame you for interpreting it the way you did. It had me scratching my head for a while.

    Style note for all journalists everywhere: never use the phrase ‘potentially fatal’ without identifying what could be killed.

  20. 20
    Violet says:

    I posted before I read your comment. I’ve used dishwashing liquid! Works pretty well!

  21. 21
    cmorenc says:

    On a somewhat related note, I’m growing basil seasonally but also have five year-established rosemary bushes nearby which I hope to grow into a belly-button high perennial hedge. However, some sort of tiny mite seems to persistently be attacking them, with the effect of slowly sucking the sap out of the leaves and leaving them mottled white/green, draining the plants of vigor. I noted that one “organic” anti-bug spray I’ve been using on the rest of my herb garden has as its main active ingredients four highly aromatic plant oils, including clove, olive oil, peppermint, and rosemary. That’s worrisome that I have a mite infection that eats the sap of one of the main anti-insect ingredients in this organic “insecticide”, which supposedly not only repels, but is actually fatal to a great many bugs.

    I have sprayed them with an organic soap-like substance (mostly sesame-oil based) that supposedly smothers them, which seems to control the infestation for a bit, but they always seem to vigorously return. Suggestions?

  22. 22
    Tom Betz says:

    @Violet: Cream is much more tasty than Dawn. Even after it has curdled!

  23. 23
    Napoleon says:

    Of course I come home from work yesterday to find a nearly biblical size swarm of beetles trying to eat all my basil.

  24. 24
    Li says:

    That’s the benefit of using sesame oil as a carrier lipid; most bugs disdain it, and it has antibacterial properties. Three pathogenic problems with one stone! And it tastes good!

    Go to asian markets, you can find the stuff real cheap there.

  25. 25
    Violet says:

    @Tom Betz:
    It sure is.

    Have you tried vigorously spraying the rosemary to knock off the mites? You’d have to do it pretty much every day. Not sure if that would work with what you’ve got, but it works with some pests.

  26. 26
    Violet says:

    Found this with various suggestions for rosemary plant pests.

    Spider mites are little tiny bugs that like to drink the sap from different types of leaves. As they drink the sap they also inject the leaf with a poisonous toxin causing discoloration to the leaves. You can get rid of spider mites by forcefully removing them with a high pressure stream of water. Repeat as needed. If the problem persists, you can use an approved pesticide to remove the spider mites.

    The water idea might work.

  27. 27
    Origuy says:

    My basil should be ok, since I’m in California. However, I’ve got a whitefly infestation in my fuchsia that I’ve been fighting with ladybugs. The darned things fly away, though.

    I found a page from Clemson University that might be helpful called Less Toxic Insecticides.

    You could try a eugenol preparation for the mites. Eugenol is in clove oil so it smells nice and is not toxic to mammals unless you consume a lot of it.

  28. 28
  29. 29
    catclub says:

    @Phoenix Woman:
    and @ Joel

    “They put faulty basil in the Ratatouille!

  30. 30

    @catclub: “Meeester Faaaaaawwwty!”

  31. 31
    Platonicspoof says:

    Couple quick (gotta go do my own preventative chores) references, if only for search terms.
    Concentrations, variations and targets.

    Serenade and related products also have an antimicrobial Bacillus.

  32. 32
    Katherine Hunter says:

    luckily you can make pesto with almost “anything” : kale (use pecans), cilantro (use pistachios). “Genovese” is the only pesto that absolutely requires basil.

  33. 33
    goatchowder says:

    “Downey Mildew” was the name of a great college-rock band in Los Angeles in the 80’s.

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