Scale – on houseplants

Raise your hand if your houseplants don’t have scale. Anyone, anyone? If they don’t, I’m willing to bet that either Mother Nature loves lucky-you especially (though she may have another plague in store, beware); you have only four houseplants, all begonias; or your plants have been infested with scale insects in the past and you have somehow managed to banish it from your house. If your plants do have scale, don’t be embarrassed. You’re in good company (says me).

scale, honeydew and sooty mold on a dwarf kumquat I freely admit to having disgusting scale on a few of my plants at home. (For Mr. McGregor’s Daughter’s houseplant census, I also admit to having upwards of 85 plants inside my approximately 1000 sq. foot house…) And I’m sorry to say that ever since we stopped using systemic pesticides, a few scale have found their way back into the greenhouse here and there. If you’re not already familiar with these sapsuckers, scale generally look like crusty brown or waxy yellowish scabs and are often found on the underside of leaves along the midrib, tucked into leaf axils or along the stem. (Mealy bug is also a type of scale which resembles sticky grey cotton goo.)

Scale life-cycle in a nutshell (ha!): Eggs hatch under the protective shell of the female and start their life out as “crawlers”. They don’t travel far or fast – but that would explain how they get from plant to plant especially in a cheek-by-jowl living arrangement. Once they’ve found their spot they lose their legs and settle in for a suck. After molting and morphing into their adult selves, male scale grow wings but lose the ability to eat (no mouth). Males use their day or two window of opportunity to search for and mate with females. Females meanwhile develop a crusty protective shell from their castoff molts.

I have never noticed any flyers, eggs or “crawlers” but I guess I haven’t paid very close attention. I do always notice a fresh crop of immature scale (the small yellowish ones), their honeydew poop and the opportunistic sooty mold that sticks to it. I periodically – probably once a week at home – put plants in the sink for a bath and I go after the individual scale with an insecticidal fingernail.

The recommended treatment (besides systemic pesticides, or introducing another insect into your house to eat the scale – which might be worth a try) is to scrape them off and give the plant a dilute soap and/or horticultural oil wash and a water rinse. But take care to test your chosen method before treating the whole plant. Ferns, for one, are notoriously sensitive to anything but a gentle fingernail and room-temp water, and citrus don’t love oil.

So, fess up now – do your houseplants have scale? What do you do?

2 thoughts on “Scale – on houseplants

  1. Earlier today, I came over here from Mr. McGregor’s Daughter, and saw this, and started writing a comment to you about how I’ve never actually had a case of scale on any of my plants at home. Spider mites, sure. Mealybugs, more often than I would like. Even aphids, once. But never scale. And I was going to attribute this to a combination of luck and clean living.

    Then I thought, No! I’ll jinx myself if I publish this comment! and deleted it without posting.

    So today, while watering, I found my very first case of scale at home, on two Neoregelias that I like too much to discard. I’ve just spent about half an hour trying to rub all the visible adults off with a wet paper towel (unpleasant! The Neoregelias in question have sharp, outward-pointing marginal spines.), and then I put systemic pesticide granules in the soil, and now my hands hurt.

    This somehow feels like it’s your fault.[1]

    Also I think it’s really, really unfair that just thinking about posting a comment can jinx a person as thoroughly as actually posting it. I think I should get some credit for deleting the comment. But no.

    *sigh*

    -

    [1] (I know that it is not actually your fault.)

    Mr. Subjunctive, I’m so sorry! I never even considered liability issues before posting this. I’d say that 2 out of 822 isn’t bad but am afraid that might get you into more trouble. (822 houseplants?! You win.) I do think it’s wicked of scale – and typical – to choose the spiny plants. If it’s any consolation, my cuticles are bloodied on a regular basis. -kris

  2. I haven’t found the miracle cure to get rid of scales yet (even though I never had any when I was living in Wales), but I control them by spraying the plant with a mixture of oil and water. It works for a few month. In summer, I leave them outside and is seems scales don’t come back as long as the plant is outside.

    Isabelle, I can’t wait to be able to move everything out… My only trouble with the oil is that the citrus don’t just love it. Otherwise, it works like a charm. -kris

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