Green ideas for pest control?

Getting a program for spring and summer pest control underway for the bonsai yard can involve thoughts on green pest management. Predatory and parasitic insects sound great, right? Buy a bottle, wave it around your bonsai, and sit back with a bloody mary and assume great and devastating things going on in miniature, the remains of your aphids, caterpillars, and spider mites strewn right and left.

Sadly, predatory and parasitic controls are rarely solutions to a pest problem for the average hobbyist’s bonsai yard.


The familiar and popular ladybug, an aphid predator (if you can get the adults to stick around long enough)

For a small cluster of bonsai on a few benches in the middle of a half-acre of grass, or a couple bonsai on rooftop garden in the city, green pest controls will likely be very disappointing. Both these places have one huge minus for supporting predation:

The absence of a functioning ecosystem.


Terrible place for biodiversity and green pest controls…a lawn


A brilliant place to simply leave alone with natural controls…a meadow

We might buy some ladybugs and release them, they fly away, the kids squeal and clap, and that’s about it. Ladybugs look great, and are a kind of poster-insect for green pest management, but will tend to colonize the neighboring yards rather than your bonsai.


The much more effective aphid predator, the ladybug larva, which will keep eating voraciously until there are few aphids left on one plant

For many full, established backyard gardens, though, green technologies may be a good path. Particularly those gardens that have a vast array of plant species in them, and especially those gardens that are dense and stable. Meadows generally have a lot of biodiversity, for instance, and are perfect for natural controls. My entomologist father was a huge fan of meadows.

Once we take one thing out of environments like this and try to grow it, like a tree, we get into trouble…

Parasitic and predatory insects are rarely going to work for bonsai outside of these rich environments…for that to work, bonsai would need to be in close proximity to foliar biodiversity (where it is hard to see bonsai to their best advantage.)


A predatory mite (red), with an aphid (grey) it has found

If you have a situation where it might work, like a complex, full garden, by all means do look into predatory mites, parasitic wasps, and others that can often effectively control or keep in check many pest problems that could get out of hand in simpler gardens. Many green controls are already present…predatory mites are often 20% of the mite population, being the faster moving mites on your plant (or on a white sheet of paper, following the ‘brushing the branch’ test.) Surprisingly, unless you have a lot of bluebottles zipping around, up to 95% of all flies in the backyard are predatory.

Most bonsai yards are simplified for better appreciation, and unfortunately we often need to resort to other means of pest control…and we can talk about that in another post.

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  1. Dan M says:

    I recently found brown scale mites on my lemon tree when I moved it outside for spring. I tried spraying them with an alcohol/water/soap solution and it seemed to kill the majority of them but I could still see crawlers or baby mites and the alcohol spray looked to be damaging the leaves at the same time.
    I followed up with 1500 ladybugs ($7) to see if they would take out the remaining baby mites and eggs. I was worried about them just flying away as you stated, so I covered the most of the tree with a clear poly tarp first and then released the lady bugs inside. I also poured some of the hummingbirds’ sugar water on a couple of baseball sized lava rocks and placed them at the base of the tree in an attempt to keep the ladybugs around with food.
    This was 2 weeks ago, the ladybugs seemed very active and stuck around for the most part. I removed the tarp off the tree 5 days after letting the ladybugs loose. Although it was wet, cold, and windy; a decent number of ladybugs stuck around on the lemon tree. Some just hung out on the sugar water rocks but most of them just clustered in spots along the main trunk of the tree. Now, 2 weeks later I would estimate about 100 ladybugs remain on the tree.
    Results: So far, so good. I don’t see any mites, although babies are super tiny and hard to see. I agree this doesn’t seem practical for large scale treatment as most of my energy went into keeping the ladybugs on one tree. You mentioned ladybugs colonizing neighbors yards, I’ve heard stories of them colonizing inside the walls of neighbors houses and they end up with a ladybug hatch inside their house every spring. Luckily for me I only have one neighbor within 100 yards and as far as biodiversity goes I have forest, creek and swamp on 1/2 the property and orchard, meadow on the other 1/2, BUGS GALORE!!!

    • crataegus says:

      That’s a good story…
      I’d offer a caution to anyone using the alcohol/water/soap/home brew pest control. That’s very bad stuff and does damage the plant. (I tried this years ago and now buy pest controls.)

    • White vinegar is often used as a primary ingredient in natural non toxic herbicides so I wouldn’t recommend spraying your trees with alcohol.

    • As for lady bugs crawling into houses, yes they do that. They will winter in any cramped crawl space they can find that affords protection from the elements. Unfortunately this results in ladybugs in the house. My house is full of them. Also if you are releasing them, it’s cold out, and they cluster together it was too cold. They aren’t going after the pest insects, they are just sitting there waiting for the weather to warm up.

  2. says:

    Good morning Michael,   You are so right about the Lady bugs. I buy them every year and within a few days I can’t find one any where. Where could I find Lady bug larva?   We have a rumor Saturday that there will be sun that will stay around for more that a few hours. Hope they are right this time.\ Happy Easter. Hope you can find lots of Chocolate eggs. hee hee   Annette Clark

    • crataegus says:

      There are companies that sell live parasite/predators for our gardens…I just don’t know who they are specifically. I was at a seminar recently and there was a company showing vials of parasitoids that were so small they were hard to see and names so weird I forgot them immediately. Not ladybug larvae, but maybe they would be able to help you find some-

  3. I’ve question regarding pests. A couple years back one of my trees, a small two hand weeping spruce, was covered in fine webs over night. The webs were so dense it nearly killed the tree. To combat this I used a small stiff paint brush to carefully remove the webs, but I never saw any sign of what created the webs in the first place. In the end I used a wide spectrum insecticide in powdered form in hopes of getting rid of the unknown critters. Any thoughts on what it might have been?

    • crataegus says:

      Sounds like it might have been spider mites. Very small webs. And the plants will go yellowish, under a magnifying glass it will look mottled. Identify spider mites with a piece of paper held under a branch, then brush the foliage vigorously. On the page you may see very slowly moving tiny dots. Those are spider mites. You may not have the mites any more, but maybe check to see.

      Some of the general insecticides kill mites, bad infestations might require a mitacide. Just check your chemical and make sure it kills mites.

  4. carterbeall says:

    Why not just blast them off with a hose repeatedly when watering? I have found this to be the most effective method for dealing with most pest insects.

    • crataegus says:

      The problems with hose washing for bonsai are multiple. For one, it’s hard to get underneath the leaves where many pests rest, and so numbers just rebound, and also that many pests are not easily washed off, like scale. Strong blasts of water can damage new spring growth. Also, it can literally adjust fine wiring. So for several reasons hose washing is not the best practice for pest control on bonsai.

  5. thomdec says:

    Michael – I just found this post, great content. I live in San Francisco and my trees are housed on my balcony, so unfortunately I have to resort to using insecticides to control any pests. I’ve found spider mites on my pines and have sprayed them with neen oil, but need your advice as to what to use on my spruce, specifically my Engelmann. I know they are sensitive and a bit finikey when it comes to sprays, so your help would be appreciated. I want to stay as environmentally safe as possible.


    • crataegus says:

      I think it’s wise to avoid the oils and soaps for the spruces, they might lose some of the protective wax that helps them survive the intense sun. Bayer is not too bad in some situations, especially on confers that do not attract honeybees. But you might want to look into a mitacide. The labels online should give you a sense if it will work with spruce. Mitacides are not cheap, but share it around with your friends.

  6. Nathan says:

    Michael, great post here. Came across your site while doing some research. I will definitely be returning.

  7. kapillokhande2016 says:

    This information is really nice, you have great post Michael, Keep It up.
    If you want you can ream more on Pest Control over here…

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