Scale Insect – Experimenting with Treatments


So I may have mentioned previously that I recently came upon an unfortunate case of scale insect at some point in the last year or so. Sometime between moving here, and bringing plants inside, they got scale. Or perhaps a newly acquired plant did not get properly quarantined. Next thing you know, you are finding sticky splatters on the floor, sticky leaves (with cat hair stuck on them, as I find in my home), just sticky everything around it! It’s really unsightly, and left too long, it’s disastrous. I have thrown plants away that were too far infested. I remember a beautiful bird’s nest fern. It was given up on. I don’t like doing it, and I definitely DON’T doom my plants to the compost heap if I have had them a long time and grew very attached to them. Some of the ones I love dearly have had a brush with the Scale.

Where I work, there is occasionally a customer who comes in with scale problems. I usually pity them as much as Goutweed victims. There isn’t a LOT out there, in Nova Scotia, that will successfully eradicate scale, as there is no systemic insecticide available in a hardware/garden shop that you could use. And even doing so is risky, as I know a gardener who killed a few of his citrus trees from systemics. Even garden center owners I have enquired about Scale report they do the Alcohol/Q tip method. It’s just not a thing to use a systemic, and only those who boldly import from across the border typically use it. But I’m here to help you, the less ballsy gardener, who may not want to do daring feats or use potentially toxic systemics.

So let’s continue. Let’s say that you have scale. You see them, likely on new growth. Or a few here and there, on a plant that has few leaves. Check the undersides, and check the stems. They can hide very well on stems as I have discovered, almost posing as part of the natural look of the bark.  And they cuddle right into the midrib of leaves for a sap snack. If it is minor and you feel as though you can tackle them easily, you will need:
1) A bottle of rubbing alcohol (and a bowl or something to pour some into)
2) Cotton Q-tip swabs

Sit down and pop on some music. Dip your swabs in the alcohol, and apply directly to the scale. You will find it will pop them off fairly easily with only a small amount of pressure.  Depending on the type of plant that you are treating, you could probably apply a fair amount of pressure to really penetrate that scale shell and flake them off. I tried this (and gave up) on a poinsettia. That was a hard one to swallow, but I gave up before I could come up with trying a more effective solution (such as the one I have below). Citrus, ficus, and other tough leaves will withstand this treatment with no issues or bruising at all.

Once your swab is really gross, flip it over, use the other end, continue. I usually go through a lot of swabs. At first, I started treating my staghorn ferns in this method. But it wasn’t enough. 2 weeks pass, and there it was again, back with a vengeance. Now, I’m not saying there were hundreds on the plant. I would say I could find 12-15 of them on the entire plant every time I checked them again.

That’s the next issue with scale, if you can’t get it all because you don’t see it, they’ll find their way back on the plant from those crevices you missed. This is probably a moderate infestation at this point, by my standards. This is where I move to the next step.

Previously, I attempted a product called End-All. This did not work. Don’t make a special trip for it. It is quite effective on spider mites and aphids, but I wasn’t sold on the “treats scale” side of things.

20160708_073355The next thing I tried, as I saw on the label that Horticultural Oil treats Scale. So I made up a litre bottle of Hort Oil and spritzed down all of my infested plants. I treated a Ficus benjamina (Minor problems), Staghorn Ferns (Moderate), Goldfish Plant (Severe), Jasmine (Minor), and Variegated Lemon tree (Minor), and Adeniums (severe). Horticultural oil is fairly easy to get your hands on. Mine came in a box paired up with Lime Sulphur. You often find these two pals together in Dormant Spray Kits.

The result? They required 2-3 sprayings, after which, I removed my jasmine and citrus from the spray routine. After a 3rd spray application, the staghorn is showing no scale issue as far as I can see. I revisit every 7-10 days and really look them over, even if they were all clear. My Ficus, as you see in the above photo, still has scale, but it’s incredibly minor, and still receives regular sprayings until the infestation is gone. I’m also finding that ants are interfering with my efforts, and they often show me where the scale is. Ants treat scale very similarly to the way they treat Aphids. When spraying horticultural oil, SHAKE IT FREQUENTLY. Otherwise, you’re just spraying water.

Hort Oil is effective due to the oils clogging the pores of the insect pests, causing them to die. You may need to flick the dead carcasses off the leaves, as they sort of latch on once they find a host.

Depending on the severity, I will sometimes also prune the plants back, as scale might like the tender new growth. But don’t do what I did with my goldfish plant. I pruned it back so hard it was incapable of recovery. I would suggest cutting back NEVER any more than 1/3 of the new growth (Always use the 1/3 rule with most plants). So I learned from this experience.

The other thing I would reccommend is when spraying, do it in a place where you don’t mind overspray. Do it early in the day, so the plants don’t burn from the droplets magnifying the sunlight. (And definitely don’t forget your staghorn ferns in the greenhouse in the hot sun as I did…oops)

So let’s say you don’t have or want to use horticultural Oil. I have another trick I have seen used by other gardeners. The 50:50 Rubbing alcohol:water spray. This will also work, as far as I’m told, but I haven’t escalated to the point where I needed to explore another option. But if you are having this problem, you can explore this option. And if I am still fighting scale on my adeniums by fall, I will also try it and report my findings.

The other thing you can do if your infestation is severe is to repot your plant. Scale will also live in the root area/soil. Repotting will refresh the soil. With my Adeniums, because they are so tiny, I unpotted them, washed their roots and then applied horticultural oil to the root zone before repotting with fresh soil again. Their infestation problem is still a problem, which is still being treated with oil.

20160707_134124But you can see from the photo how they began as vigorous young seedlings, and suddenly, a few tiers of growth later, they got very stunted with puckered leaves. Then later, the growth resumes at a semi normal rate. This is where the oil had begun to work. (Pardon the water droplets, I had just watered them at this time) You can still see one scale on the trunk just above the lowest leaf. This one is likely dead. If they are dead and the oil was effective, they should just wipe or flick right off. They are no longer causing damage.


Always check the undersides of leaves. That’s why they always sneak up and cause visible damage before you notice them. 




20160704_191749.jpgSo how do you prevent scale?

  • Quarantine all your new plants. I know you got it from a reputable person, or your bestie. Do it anyway, you’ll be glad you did. If it’s infected, you can either spray it, or discard.
  • Don’t overcrowd your plants so that their leaves touch the leaves of their neighbors. Scale travels easily this way, and it’s a surefire way to spread many insect problems, not just scale.
  • Avoid stressing plants out by over/under watering, moving it to a bright/dark location, etc
  • Avoid putting them outside. If you put them outside, spray them well before bringing them back in. Trust me, you will be glad you did.

That concludes my Scale rant for today. Try these. Check your plants regularly, and don’t let them cuddle too close! 😉

Next week might be a mix-up post between some super simple pinterest-inspired projects and pics of the Montreal Botanical Gardens. Yay!


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