How to Treat Rose and Flower Pests Naturally: Organic Control of Black Spot/ Powdery Mildew, Aphids, and Caterpillars

If you’ve tried to prevent rose problems with the tips in this article, but still ended up with some pests (it happens!), here are the methods I recommend to get rid of pests on roses the organic way. (Obviously, before spraying anything, read the instructions on the bottle and be sure to suit up appropriately – organic choices are usually safer, but that doesn’t mean you want to get it on your skin or eyes.)

For fungus problems like black spot, rust and powdery mildew:

Safer Garden FungicideSulfur (not lime-sulfur) is an effective way of getting rid of fungus organically during the growing season, and is usually my first choice for a fungicide. I use a sulfur spray every 1-2 weeks at the first sign of a problem. Coat the under and the upper sides of the foliage well. Sulfur is harmful to beneficial mites, so if you’ve put out beneficial mites nearby, don’t use sulfur. It is safe for honeybees, though! Truth About Organic Gardening book by Gillman Jeff Gillman, author of The Truth About Organic Gardening, suggests spraying weekly with a mixture of 1 part milk to 2 parts water to treat fungus problems. Check out this quirky video here in which he mocks some organic fungicides and synthetic fertilizers. I haven’t tried the milk treatment yet, but he’s a scientific-minded fellow, so I trust that it works. I’m guessing that spraying weekly and covering every surface of the leaves, upper and undersides, are the keys to success with this method. Serenade rose disease controlSerenade, a bio-fungicide, is a new-ish spray that I’m testing in the gardens I maintain this year. Basically it is a type of bacteria (Bacillus subtilis) that attacks the fungi causing problems on your roses. Word around the nursery is that it’s effective if sprayed regularly, once a week. I like using biologically-based controls like Serenade (where one beastie eats another) because the action is usually so specific that it doesn’t harm good bugs, birds, or us. Pick the infected leaves off. This is a free and simple way to reduce pest populations, and you can do this in conjunction with any of your sprays.

To get rid of aphids:

Prevention is the best cure, as aphids just love that soft new growth that occurs from over-fertilizing, using synthetic fertilizers, or a plant not getting enough light. If you do end up with a problem, try these fixes: Insecticidal soap is fairly effective at killing aphids, while being pretty harmless to beneficial bugs. It works by sticking to a bug and smothering it, so once it’s dry it doesn’t really hurt anything. You have to keep up with it to be effective, but it’s a simple cure for a small infestation. Friendly Petals photo by audreyjm529 on Flickr via CC Attribution License You can also attract beneficial insects that eat aphids,  like lacewings and ladybugs, by planting nectar plants like daisies, yarrow, lavender, catmint/ Nepeta, and flowering sages/ Salvias. What rose wouldn’t look great with some lavender or Shasta Daisies planted nearby? If you’re trying to attract beneficials, be careful not to use broad-spectrum insecticides in your garden, like most synthetics, or the organic Pyrethrum. You’ll kill the good bugs along with the bad. If you’re going to buy beneficial insects, I’d choose lacewings over ladybugs, since lacewings often arrive in an egg form, meaning you have them for their voracious larval stage AND the adult stage. Ladybugs arrive as flighty grownups and most of them take off as soon as you let them go.

Stop caterpillars from decimating leaves:

Monarch on a Carnation photo by audreyjm529 on Flickr via CC Attribution license Now, before telling you how I kill caterpillars in the garden, I want you to think first about what caterpillars become. If you’re planting things in the garden to attract butterflies, then killing caterpillars may be counter-productive to your goals. You’ll usually find caterpillars on the undersides of leaves that have been munched, so if you see damage, turn the leaves over and look to see if caterpillars have caused it. For me, the first step is trying to pick them off. A couple caterpillars won’t kill your plant and aren’t that big of a deal. If you don’t want them on your roses, set them on your neighbor’s patch of weeds or some sturdy perennial that you don’t care too much about. If you end up with lots of caterpillars all at once, too many to reasonably pick off, there’s a biological spray that works great called BT, Bacillus thuringiensis kurstaki. It’s brewed from a soil-dwelling bacteria and it’s only effective on caterpillars, so it won’t harm beneficial bugs or birds. BT (sold as Caterpillar Killer by Safer) makes caterpillars stop eating almost immediately, though the caterpillars stay on the plant for about a week, until they die. Even though caterpillar damage can be dramatic, plants usually recover quickly and I’ve never seen anything actually die from them, so don’t worry too much if they’ve scalped your rosebush – it’ll be back!

Snails and Slugs:

Snails and slugs aren’t usually a pest for roses, but many flowers have problems with them, so go here to learn how to kill snails and slugs organically. [print_link]

Comments

  1. says

    Genevieve,

    This post is especially timely for me and probably many other eastcoast gardeners. The wet and soggy June (it rained almost every day here that month) means I have an inordinate amount of insects and fungus in my garden. I feel like all I do lately is try to figure out what’s basically cosmetic and what will actually kill my plants and then treat accordingly. I’m especially intrigued by Serenade, I think I’ll have to see if I can find any around here.
    .-= Debbie´s last blog ..Happy Bloom Day! =-.

  2. says

    I like this post on natural pest control for roses; roses seem to bring out the poisons. From most reports and my experience, I would say that black spot is cosmetic, not dangerous – but I don’t live in an extremely moist climate. (Some black spot tolerators are from the UK, however.)

    I think one of the most important (and easy) natural rose care tips is: plant roses other than those poor inbred tortured hybrid teas! I love some of the hybrid teas, but it is a fact that they are the most disease-prone high-maintenance roses around. David Austin roses are a wonderful reblooming alternative, as are many other shrub roses, grandifloras, and floribundas. Tea roses (precursors to HTs) do well in hot climates; hybrid musks are great in semi-shade; Buck Roses are good for cold climates. So are a lot of old roses, though many of them bloom just once. But beautifully. And historically.
    .-= Pomona Belvedere´s last blog ..Salvia sclarea: Clary Sage =-.

  3. says

    Debbie, so glad this is timely for you guys! Not so glad you’re having a bumper year for pests and fungus. Bummer, dude. I bet you can find Serenade where you live – they’ve been trying hard to get it out there to people, I think. They even have a (very lame) twitter account.

    Pomona, what an incredibly helpful post! I love your listing of the roses that tend to do well without disease, and I concur – those Hybrid teas are pretty but I think the reason so many are sold is good marketing more than good performance. You look at the old roses and the Austins and such and they do just beautifully without any real pest control needs. I’ve never met anyone who actually enjoys spraying for pests, so why do we torture ourselves?

    Here, Black Spot can defoliate a rose if it’s bad enough, but you’re right – it usually isn’t a terrible condition.
    .-= Genevieve´s last blog ..How to Treat Rose and Flower Pests Naturally: Organic Control of Black Spot/ Powdery Mildew, Aphids, and Caterpillars =-.

  4. S Tariq says

    My standard roses have begun drying up in spite of adequate rainfall and watering. Digging around the roots revealed large white caterpillar like bugs. I don’t want to use a pesticide on my plants – could someone please suggest an alternate remedy?

  5. Sam says

    Is it worth having Roses ? The war with all the pests is not worth it, dig them out and toss. They cost me more than my stress medicine.

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