PESTICIDE RECIPE: The Best Bug-Killing Mix for Mites, Mealybugs, Aphids, and Thrips (Works well for orchids & house plants)

In Orchid Tips & Care
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I prefer not to use systemic pesticides—they are not easily available for purchase in Canada and while they are effective at killing insects, they can also be toxic to pets and people. To be transparent, I have in select situations, used imidacloprid (a systemic) for particularly infested plants. I also used Malithion once…and I’m pretty sure I knocked 5 years off the end of my life. If you are going to opt for systemic pesticides rather than the less-toxic option outlined below, go for something that isn’t a spray-on application (which will increase your chances of inhaling it) and read/follow the safety precautions closely. There are some granular application types which can be sprinkled into the potting mix and reduce your general chance of toxic exposure.

General Notes About Application

  • Using the non-systemic pesticide recipe below will likely not be a “once and done” application.
  • You’ll want to repeat application 3-5 times in order to ensure the pest (and subsequent egg-hatched babies) are all killed. Speaking from experience, it is more difficult to broadly treat a large collection (say over 50 plants) because you kind of end up spot-treating your collection rather than eradicating the pest all at once.
  • All it takes is one single surviving pest to restart the infestation cycle and most pestiferous insects reproduce asexually. So, start treatment at first sign of a pest, treat all plants if possible, or at least all plants near the infested plant, repeat treatment a few times after visible insects are gone, AND consider proactively applying this to new plants when you bring them into your home.
  • Non-systemic pesticides require insect contact in order to work best. Soak the plant down and coat the leaves above and below with 2-3 liberal applications at each treatment; there are more detailed directions on application down below the recipes (keep scrolling).
  • How it works: the soap changes the surface tension of the water helping the oil mix with the water and the oil smother the pests, suffocating them. If the insect escapes your initial sprays, the neem oil will help inhibit its feeding and slow its growth and reproduction cycle.

Kill Spider Mites, False/Red Mites, Mealybugs, Aphids, and Thrips

Ingredients for the Best Bug for Killing Pesticide

  • 1 cup – Water
  • 3-4 drops – Blue Dawn Dish Soap; not sure why the blue version is preferred, but it works for me and is widely recommended, so I’m not arguing it.
    • Substitution: 1/2 tsp – Dr. Bronner’s Peppermint Soap – after hearing the value of this from a few sites and from Glen Decker from Piping Rock Orchids I used it for a while. I have since stopped using it because the soap and neem oil would make a bit of a clumpy-slimy mess on my shower wall and in the spray bottle. I prefer the Dawn soap because it seem to offer a more consistent and even application—but see what works for you.
  • 1/2 tsp per cup of water – Cold-Pressed Neem Oil is a good choice
    If you can’t find neem oil at the garden centre, check your local health food store in the Skin & Ointments Section; cold pressed neem may also be a solid at room temp, so you might need to heat it slightly before adding it to your soap/water mix. Just float the container in a warm cup or bowl of water. Neem works by affecting the feeding and growth cycle of insects.
  • 1/2 tsp per cup of water – Horticulture / mineral oil
    If you can’t find neem oil, use a full tsp of mineral oil per cup. I have used baby oil in a pinch and I’ve heard of people using vegetable oil too…but I don’t recommend that in case it goes rancid on your plants.
  • Optional: Some people use 1/2 ratio of isopropyl alcohol to 1/2 water.
    *I don’t but I have used straight ethanol rubbing alcohol (70%) for spidermites and mealybugs (in addition to this above recipe). In that case, I’ll apply the rubbing alcohol first, wait 15 mins and then apply the oil-soap mix.

Added Oomf / Additional Bug-Killing Power

Other oils. I have since stopped using different oils because the smells bothered me and I have generally decided that it’s better to use things that have been specifically tested on plants. Some of the concentrates may burn or harm plant leaves, so it becomes more experimental using these. Many of my plants are slower-growing orchids, and it can take them years to recover from toxic shock, so have abandoned these in favour of neem and mineral oil only. That said…others have had great success and some of those oils used include:

  • Cinnamon oil / extract (10-20 drops)
    Stinks—makes your whole house smell like cinnamon (which sounds nicer in theory than it does in practice).
  • Eucalyptus oil / extract (10-20 drops)

Directions for Applying this Home-Made Pesticide to Infested Plants

  • In a spray bottle mix the above ingredients.
    If using neem that is solid at room temp, start by adding 40% warm water, shaking it to blend the oils and water, then add the rest of the cooler water to top-up the spray bottle.
  • At each application shake before use. The oils will separate out over time and you need to re-distribute into the water before application.
  • At each treatment you’ll want to spray the plant down 2-3 times just to make sure you’ve fully coated the insects.
  • Generously spray the plant down. Get the tops & bottoms of all leaves, and also cover the stem, trunk, petioles, inflorescence, etc. Pay special attention to coat any visible mites, aphids, thrips, mealybugs or whatever bug you’re trying to kill. Consider spraying the top of the substrate/soil as well.
  • Let plant sit for 5–10 minutes.
  • Spray a second time liberally; wait another 5 mins.
  • Optional: Spray a third time.
  • Optional: finish by rinsing the leaves off with clean water; let the water run through the potting mix for a while too to rinse out any soap. You can leave the oil on (which may be more effective), but you may increase your chance of leaf spotting or even leaf burn as the stomata may be blocked by oils reducing the standard cellular functions.
  • Repeat treatment in 5-7 days.
  • Repeat treatment in 5-7 days for a total of 3-5 applications.

Tips for Mealybugs & Thrips (hard to kill bugs that camp out in the soil or at the roots):

If you really want to get rid of pests on a plant, I suggest repotting it the first time you do this application. Spray the leaves, the stem, AND the roots…nuke the plant with the spray after you’ve unpotted it. Toss the old potting mix which can have eggs and or nymphs (ie. Thrips) and repot after you’ve completed the round of sprays for a single application. I have eradicated spidermites and false mites with a single application by doing this—but you should still reapply the spreay 2 or 3 times after, to be safe.

Tip for Spider mites (the kind that make webs):

Use a really fine atomizer spray bottle and just make a nice clouding mist around the plant from top to bottom. The webs will grab the droplets and the spidermites are hooped b/c they cant walk around without getting stuck in oil. I don’t even drench plants that have these, I just give it a good and even misting spray a couple days in the week, followed by a shower at the end of the week and the spider mites are gone for another year.

Tip for False/Red mites (the kind that don’t make webs):

These things are a pain and will be all over the plant including on the roots and in the pot. Make sure you fully drench the plant if you have false spider mites…for orchids like phals and jewel orchids, it’s a good idea to repot them and spray the roots. If you’re not going to repot…then run that mix through the potting media a couple times so that it kills any on the roots or in the media.

Caution: Test this home-made bug spray first

Before you go spraying ALL of your plants with this mix, you may want to test it on your plants. Also, know this: orchid buds and blooms do not do well with alcohol or soap on them. I lost a giant spike on my Phal. Malibu Madonna that had over 20 flowers on it when I sprayed—all of the flowers: DEAD.

Why does this non-toxic mite, mealybug, thrips and aphid killer work?

The soap reduces the surface tension of the water and allows the oil to mix. The soap also has that surface-tension changing property on the bug’s waxy outside layer…so insects that can normally repel, now can’t. The ratio of water to oil helps distribute/dilute the oil so you’re not coating your plant in a thick layer of oil. The diluted oil is enough to coat the insect and they suffocate. In the cases where a bug is able to avoid suffocation by the mineral oil, the inclusion of other oils like neem, cinnamon, or eucalyptus make the plant surface less ideal for the bug. Neem stops them from feeding so it’s the best. Cinnamon burns my mouth…so I assume it does the same to the bugs. And Eucalyptus is likely toxic to many bugs…so it just makes sense.

Anyways, the point is, this mix suffocates and drowns your bugs but any insects that survive as eggs or on a non-treated plant can restart the infestation…so be vigilant about your application.