How to use rubbing alcohol to kill mealybugs, spider mites, aphids and scale
Before you jump in and start using rubbing alcohol to get rid of pests on your plants, it's important to check you have the right product and are using it at the right dilution rate so your plant can handle the treatment. Coming up is what to look for so you get the right type of alcohol, what the dilution and application rates are for different plant pests, and how to keep your plant safe so it's only the pests you say goodbye to!
Which plant pests does rubbing alcohol kill?
Rubbing alcohol is very effective for soft-bodied pests including mealybugs, scale, spider mites and aphids. It's especially popular for pests with a waxy coating (such as scale and mealybugs), because that coating makes them difficult to kill with other pest treatments. Coming up are the specific directions for Mealybugs, Scales, Aphids and Spider Mites...
Is rubbing alcohol the same as isopropyl alcohol?
Yes and no. Rubbing alcohol contains isopropyl alcohol, but at a lower concentration. Before you use the treatment dilution rates below, check what percent of isopropyl alcohol your brand of rubbing alcohol uses. Rubbing alcohol varies between brands but for use to kill pests on indoor plants, the general advice is to avoid going over 70% alcohol.
Precautions: Is rubbing alcohol safe on all plants?
No, some plants are more sensitive than others. Unless you're confident your plant is not sensitive to rubbing alcohol or dish soap, dilute as per the directions below, and do a test patch first and just treat a couple of leaves. Always avoid getting rubbing alcohol on roots, especially undiluted.
How to do a patch test: Apply to one or two leaves and wait at least 2 days / 48 hours. Look for signs such as leaf scorch. If you do see a reaction, either do not treat the rest of the plant, or dilute more than usual and patch-test again before treating the rest of the plant.
When to apply: As with any insect treatment, it's best to apply early morning or early evening, and apply on a day not expected to reach over 30 degrees Plants being treated should always be isolated (if they are movable) or if they can't be moved, shift away nearby plants if you can. Avoid direct sun on leaves during treatment.
Treating pests comes with risks: There is always some risk involved in treating any plant with any insecticide or non-insecticidal treatment (including soap). Some leaf browning, wilting or leaf drop are common. This should come right relatively quickly, once the pests are eradicated, and your plant can put out healthy growth again, without pests damaging foliage or stunting growth.
Directions for using rubbing alcohol to treat mealybugs, aphids, scale and spider mites
READ BEFORE FIRST USE: Check precautions above as some plants are more sensitive to alcohol than others. Some plants will need a more diluted rate depending on how sensitive their foliage is (eg: 1 part rubbing alcohol with 4 parts water, instead of 3 parts water). Following are shortened directions for use by pest, however these are a guide only because rubbing alcohol is a 'DIY treatment' for plant pests, so you won't find this on the label. You can also search 'rubbing alcohol + [pest name]' online for more advice. For best results use a super fine spray mister for better coverage and better contact with the leaf surface and pests.
MEALYBUGS: Isolate the plant. Dip a cotton bud, cotton pad or similar in rubbing alcohol (undiluted). Press on-to then wipe off visible adults for instant kill. Then treat the entire plant with a mix of 1 part rubbing alcohol with 1 part water and a couple of drops of liquid dish soap. Stir then spray foliage thoroughly, including stems and (lightly), the top of the soil (do not pour mixture on to roots or drench the soil). Wait 5 to 10 minutes. Spray off and rinse thoroughly with plain water. Repot if needed. Repeat fortnightly until gone (check detailed mealybugs treatment directions here). As mealybugs are a type of scale, you'll typically need to follow up with a systemic to stop them coming back as they are excellent hiders. The systemic I use is linked below.
SCALE: Isolate the plant. For a light infestation, dip a cotton pad or cotton bud in rubbing alcohol (undiluted), and dab on then wipe off visible scale. For a more serious infestation, spot treat (undiluted), and also spray the rest of the plant with diluted rubbing alcohol. Mix 1 cup rubbing alcohol with a tablespoon of liquid dish soap (see soap recommendations coming up), and 1 litre of water and spray foliage and stems. Repeat every 3 days for at least 2 weeks. Scale is best followed up with a systemic also to stop them coming back as they are excellent hiders.
SPIDER MITES: Isolate the plant. Use undiluted rubbing alcohol for best results, or for sensitive plants (test first), mix 1 part rubbing alcohol to 3 parts water, and wipe leaves (top and bottom), with mixture. For best results follow-up with the diluted mixture in a spray bottle, applied to foliage, top and bottom. Leave for 1 to 3 hours and rinse off dead mites with plain water. Another popular combination against spider mites is 1 tablespoon of liquid dish soap, 1 litre of water and 1 cup of rubbing alcohol. Mix and apply as both a wipe and a spray, rinse off 1 hour later. Repeat every 3 days for at least 2 weeks.
APHIDS: Isolate the plant. Make an insecticidal soap and alcohol solution, using 2 parts rubbing alcohol, 5 parts water and 1 tablespoon of liquid dish soap (pure castile soap is best, see the link below for the brand I use). Spray foliage and stems liberally. Although time-consuming and fiddly with how small aphids are, you can also spot treat aphids directly using undiluted rubbing alcohol on a cotton bud or similar. Rubbing alcohol kills aphids almost instantly on contact but a spray treatment is usually needed for anything except a very light infestation caught early. Spray or spot treat (or both), every 2 to 3 days, for at least 2 weeks.
What systemic is best for hard-to-kill plant pests?
If you've already got rid of them once but they are back again, try a systemic insecticide. I use Groventive for those in New Zealand, or if you're overseas have a look at Captain Jacks Systemic on Amazon. A systemic stops them getting established again by working from the inside of the plant and kills pests when they feed. Rubbing alcohol acts as a contact insecticide for an instant kill, it's not a systemic. To fully eradicate pests and stop them coming back, you'll often need to use both.
What type of rubbing alcohol is used for plants?
I use (and sell) this brand: Isocol Rubbing Alcohol (that's if you're also in New Zealand) which is 64% isopropyl alcohol, but you can also get rubbing alcohol from your chemist, hardware store and some supermarkets. If you're not local, Whole Foods Market 70% Isopropyl Alcohol is another good option that's easy to find online (that link takes you to Amazon), and in-stores. Just make sure you check the label before you buy. Some brands still call it 'rubbing alcohol' even when it's over 70%, but keep in mind the dilution rates above are based on using maximum 70% alcohol.
What type of liquid soap is best for plants?
When using dish soap on plants, plain liquid soap without scents or other additives is best. Pure castile soap is often recommended for plants for that reason. Dr Bronner's is probably the best known brand of pure castile soap and is available in New Zealand from most chemists and whole food stores, or for my international plant friends you can get Dr Bronner's Pure Castle Soap Unscented on Amazon too.
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