Gardening Laidback Gardener Tip of the Day Pesticides

Using Alcohol to Control Pests


One homemade insecticide that can really do the job is 70% rubbing alcohol (isopropyl alcohol). Mix 1 part rubbing alcohol to 7 parts water and spray it on plants affected by aphids, mealybugs, thrips,  whiteflies, etc. The alcohol will melt the protective wax that covers certain insects and dries the soft body parts of others, leading to their death. Furthermore, alcohol spray tends draw mobile insects out of their hiding places, making them easier to control. Simply spray the solution to saturation, covering all surfaces, including stems, both sides of leaves, and especially leaf axils where so many pests tend to hide.

You can also add a few tablespoons of rubbing alcohol to insecticidal soaps and to other homemade insecticides to increase their effectiveness.

This treatment is most effective against nymphs and adults, but, depending on the species being treated, doesn’t always work on eggs and pupae. If so, they’ll soon awake to try and retake control of your plant, so you’ll have to spray again every week or so until you no longer see any pests.

A Tip to Ignore: Cotton Swab Versus Mealybug


On other sites, you’ll see the recommendation you can control mealybugs by touching each with a cotton swab dipped in rubbing alcohol… but I’m not going to waste your time. That simply doesn’t work. Yes, directly touching the insect with alcohol will kill it, but you’ll only be treating the most visible pests. Others are always hiding in places where you can’t see them and soon the infestation is back again, as bad as ever. Spraying with alcohol is more likely to get to all the insects and thus to be effective.

Beware of Intoxication


Yes, I know rubbing alcohol is a pharmaceutical product widely used to in hospitals to rub down bedridden patients. It is also the main ingredient of many hand sanitizers. Even so, it is poisonous and you can become intoxicated by rubbing alcohol fumes if you use it in an enclosed area. There is no problem with using it outdoors, but always ventilate the room when you use it indoors.

Whisky Versus Pests

Of course, you can replace rubbing alcohol as an insecticide with just about any other type of hard liquor… but I’m not sure that killing a few aphids is really a good use of 20-year-old Irish whiskey ! Rubbing alcohol is much more affordable.

Larry Hodgson is one of Canada’s best-known garden communicators. After studies at the University of Toronto and Laval University where he obtained his B.A. in modern languages in 1978, he succeeded in combining his language skills with his passion for gardening in a novel career as a garden writer and lecturer. He has notably been editor-in-chief of HousePlant Magazine, Fleurs, Plantes et Jardins, À Fleur de Pot and Houseplant Forum magazines and is currently the garden correspondent for Le Soleil and radio garden commentator for CKIA-FM Radio. He is a regular contributor to and horticultural consultant for Fleurs, Plantes, Jardins garden magazine and has written for many other garden publications in both the United States and Canada, including Canadian Gardening, Harrowsmith, Horticulture, Fine Gardening, Rebecca’s Garden and Organic Gardening. He also speaks frequently to horticultural groups throughout Canada and the U.S. His book credits include The Garden Lover’s Guide to Canada, Complete Guide to Houseplants, Making the Most of Shade, Perennials for Every Purpose, Annuals for Every Purpose, and Houseplants for Dummies, as well as nearly 50 other titles in English and French. He can be seen in Quebec on French-language television and was notably a regular collaborator for 7 years on the TV shows Fleurs et Jardins and Salut Bonjour Weekend. He is the President of the Garden Writers Association Foundation and the winner of the prestigious 2006 Garden Media Promoter Award offered by the Perennial Plant Association. An avid proponent of garden tourism, he has lead garden tours throughout Canada and to the gardens of over 30 countries over the last 30 years. He presently resides in Quebec City, Quebec.

5 comments on “Using Alcohol to Control Pests

  1. Pingback: Help! My Orchid is Losing its Leaves! – Laidback Gardener

  2. with Cpvid going on, it’s hard to obtain rubbing alcohol in grocery stores.
    So I bought a cheap bottle of gin, which is made from Juniper berries, to mix with insecticidal soap and spray my cymbidium orchids for roaches. I have the small German roaches in my house and have not been able to get rid of them.
    So far they don’t seem to be harming the leaves or the pseudobulbs, but they appear to be eating the growth tips of the new roots coming out on the hew vegetative growth.
    I can order rubbing alcohol on Amazon, but it is overpriced now and you have to pay for shipping and wait for delivery.
    I think that you can have iIt shipped to you from WalMart, but haven’t checked that out yet.
    One of my cymbidium plants got root rot and killed the lead growth on it, so I am putting cytokinin paste on the back bulbs and using rooting powder.}
    I didn’t see any old dormant growth nodes on the back bulbs, but two days ago I saw a little green shoot popping up from beneath the growing medium.
    I am afraid I will kill the existing roots with too much insecticide, and the alcohol seems to dry the old roots out. If this plant is going to recover I don’t want the new growth killed off by insects.
    My other plant has a new growth shoot coming up and what look like two potential flower spikes waiting for blooming season to arrive. I don’t want bugs eating the flower spikes and especially not the flower buds or blossoms.
    I’m going to get some sticky traps to put in the pots to catch a few “incoming” roaches but the ones crawling on the bulbs and the roots are the ones I need to deal with without damaging the plants or the flowers. I wonder if Diatomaceous earth would have any effect on the bugs, or if it would harm the plants. They say once it gets wet it loses it effectiveness against bugs, but if they eat the stuff it seems like it should mess up their digestive tracts..
    I want to try the Neem products, but I bought some Neem hand soap once and iit smelled horrible.
    Any suggestions or knowledge about fending off roaches would be appreciated. The man from the city said that these roaches are a plague here in Phoenix, and even very fine homes and business with a lot of paper files on shelves have to be treated several times to get rid of them.
    They also have no inhibitions about crawling on people, and if one of them is on me and I smack it, I am allergic to something in them and that spot will itch for hours.

    • First, diatomaceous earth is only effective when dry, but it works not because insects eat it (they don’t), but because it has sharp edges (dulled by water) than cut their bodies. You could put DE all around pots and that would keep roaches out… if they’re not already hiding inside the pots, that is. Or cover tender tissues and flower buds with DE (and not spray with water). They’ll look dusty, but insects won’t be able to eat them.

      For roaches in general, though, my only expertise is on plants, and it seems to me that this is more of a household problem that spills over onto plants. I’d suggest seeing an exterminator and following their suggestions.

  3. I read many articles saying that IPA(isopropyl alcohol) kills mealy bugs, and many says it kills them on contact. on testing, this is simply not true.

    I found some mealy bugs on my tillandisa harris plant. I capture 1 mealy bug and tested the IPA on it. It didn’t kill the bug. Some articles say it will turn brown meaning it is dead. Not true. The bug turn brown/reddish brown, but still moves around even after a few hours. it is so disappointing.

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