Death to scale bugs - help me brew up some organic death spray to save my citrus trees

The scale got so bad on my potted lemon and lime plants before I noticed and now I'm scraping it off daily.  But it's still not enough.

The plants spend the summer outside and they are bug-free, but it's not warm enough to keep them outside year 'round, so I bring them in for the winter, and that's when the scale takes over.  

I tried the organic spray from the shop, but it's citrus.  The plant is citrus.  The scale bugs like the plant and they seem to LOVE the spray.

There's got to be a better way.

Anyone got some organic or better homebrew recipes for killing scale so my citrus trees can overwinter in peace?  

Soap. Plain dish soap works pretty well on scale and because citrus leaves are thick and waxy it won't bother them too much. Reapply after rain and after a few cycles you should see the scale start to drop off. It's most effective on the younger instars, as they haven't developed the hard shells yet, so repeat applications get the population down through attrition. Neem is effective as well but soap is cheaper.

I give my plants a shower in plain old water.

My scale aren't responding to water.

Or soap.

They have a shell on them that seems to protect against this.  But they do move around.

Either I need something that can penetrant the soft protective layer, or something that will coat the leaves that damage the bugs but not the plants.

Or.... figure out more about the life cycle and attack them younger.   Are they ever grubs?   If so, where?

How are you applying the soap? In what concentration? And like Phil said, it takes repeated applications and some time to see results.

I don't remember anymore what kind of plant it was, but we used to have one that got scale quite badly. I'd scrap off the bulk of it, then spray every day with very soapy water, turning the plant sideways so I didn't get too much in the soil.  It did work, but I'd have to do it every winter when the plant was unhappy due to low light.

My philosophy now is that if a plant doesn't like my conditions or how I treat it, I don't want it...even if I really, really want it! I've got a mandevilla vine right now, rescued from the yard waste recycling place, that gets spider mites in the dark winter. I'm seeing if cutting off pretty much all the foliage and just letting it regrow every year will work, cause it's very beautiful. But if it doesn't work, it's gone.

Oh, and spray from all directions. Make sure tops and bottoms of the leaves get hit.

I just did a search and apparently rubbing alcohol, ideally applied directly to the scale will kill it. Probably a good idea to test a leaf to see how the plant responds. For widespread application 1:7 with water and sprayed to completely coat every bit of the plant is what's suggested. Just like when I spray my plants, I'd do it outside and turn the plant this way and that to get every surface.

r ranson wrote:

Or.... figure out more about the life cycle and attack them younger.   Are they ever grubs?   If so, where?

The eggs are laid under the protective shell of the mature ones. The nymphs move around, and that's when they're weakest. Something like dishsoap or oil will coat their respiratory openings at that point. But there are still eggs waiting to hatch and mature ones that need repeated applications or to be scraped off. That's why it takes time.

With my lifestyle,  a mix I can spray on the plants after my daily bug hunt would be ideal.  

We've got Soap and water 1 to 7.  I bought some unscented dr B for this.

Some of the mixes suggested adding alcohol to the mix.  But would it work?  Seems too watered down to do anything.

I didn't really measure my soap, but I'm almost certain it was more concentrated than 1:7. Castile soap is thinner than the dish soap I use. Not sure how that translates.

Some home treatment tips.

Jan White wrote:I didn't really measure my soap, but I'm almost certain it was more concentrated than 1:7. Castile soap is thinner than the dish soap I use. Not sure how that translates.

Dr Bronner's is very concentrated, so I'm sure it's a fine dilution.

I have never encountered scale insects. I had to look them up, so maybe what I am about to suggest is useless to you and your problem.  However, when I have an infestation I usually go for the bicarbonate of soda and neem oil,

I dilute a teaspoon of neem oil in some organic washing up liquid or castille soap, add it to a one litre spray bottle of water to which was added 2 to 3 teaspoons of bicarbonate of soda.  Shake well before use and spray the plant over and under leaves. Repeat.

If you do not have, or like neem oil, you can replace it by a teaspoon of olive olive in which was added a couple of drops of essential oil of cloves or eucalyptus.  Maybe both for good measure, though I've never tried that.

It would be nice to know if you have managed to save your plants, whatever the method you've used.  Good luck

It has been a while, but if I recall correctly, I used neem oil on a scale infestation on a potted gardenia along with manual removal.

Try taking a close look at the immediate environment of the tree - what is making it weak and thus a target for infestation? How's the soil ph? Is the topsoil draining well enough to enable the water to reach deeply for the entire root system? Too much shade, maybe on one side? Another plant around that it doesn't like? The healthiest plants do not become hosts for pests. Also, painting lime on the trunks from the ground up 2-3 feet prevents pests from climbing up, it's a desiccant that they can't abide. Won't deter airborne pests but will prevent the ants which move in to cultivate the scale bugs.

On my citrus trees, where there's scale there are ants.  The ants milk the scale and in turn protect them, and even move them around.  So part of the solution is to stop the ants from moving up the tree(s).

Soap wise, I use Safer Soap, which is a concentrate containing the potassium salts of fatty acids. It is inexpensive, certainly costs  less than neem oil, and very easy to mix and use.  I mix 1 1/4 tbsp of the concentrate with 1 quart of water.  The soap mixes mentioned already seem to be very dilute and  Safer Soap is considered more effective (and easier on the plants) than the dish soap mixes.

I don't know if any soap will penetrate the scale hard shell, but at certain intervals (temperature ranges?) the baby scale (nympths) are outside and moving around and very vulnerable to soap sprays.  I also have used rubbing alcohol sprayed on the hard  scale and it seems to make them easier to wipe off...I don't know if it penetrates the shell and kills them...I use straight undiluted isopropyl alcohol.

Ladybugs and predatory wasps are good to control them, have you try to encourage them to live in your garden ?

How did it go?

On my young citrus seeds (outside) I occasionally get scale, with and without ants. Without ants, when it's bad I use alcohol on a q-tip to get them off, then spray the plant with dilute soapy water. Obviously, works better on a smaller plant than a large tree.

I do find that whether I use alcohol or soapy water, i need to physically move the bugs or it doesn't do much. so i may spray soapy water and then rub my fingers on the branches to dislodge the little monsters. then maybe hit with the hose, and spray soap again.

Isopropyl alcohol had been mentioned a couple times, but that's what I use. Everywhere on the Internet I see says to dilute it, because it might hurt some if your more sensitive plants, but I never do.  A, I've not yet found a plant sensitive enough to care, though I've not tried it on my flytrap yet.  The pitcher plant didn't care, neither did my citrus trees when I had them.  And B, I figured at this point, either I'm going to kill them trying to kill off the infestation, the infestation is going to kill them, or I'm going to dispose of the plant before the rest of my indoor jungle is infested. I put it in a spray bottle and spray the whole plant until it's dripping off.  I would try to avoid so much that it's dripping into the pot, maybe turn it sideways like someone suggested with the soap.

First though, go through and manually remove every one of the scale bugs you can find, pay close attention to the undersides of leaves and to joints. If you have a particular heavily invested spot, consider if the plant can stand to have that spot removed entirely. As someone else mentioned, they lay eggs. If you remove the branch, eggs and all are gone. I would either incinerate or garbage the clippings, rather than risk contaminating my compost.

Also, if you haven't already, inspect every plant nearby. If you have a heavy enough investigation, and it sounds like you do, these videos will spread from the initial host to whatever is nearby. They are much easier to deal with when they're just a few of them.

Also, again because of the eggs, you'll have to keep going back every day or three and play the removal game again, until you manage to kill the very last one from the very last egg. This will probably take the better part of a month to get the last, though total number of the pests should drop of fairly sharply.

Insects employ water repellent coatings to protect themselves. Soap, oil or alcohol are used in an attempt to overcome the water repellency, by acting as a wetting agent, and clogging their breathing pores, or creating some kind of imbalance that can weaken and kill them. But that means that these measures only work if applied directly to the bugs, fully coating them. Scale bugs hold onto leaves like limpets, and that makes it difficult or impossible to wet the underbelly where the pores are, and physically wiping them off might be your best option.

Another alternative method for hard shelled insects is to physically compromise their coating, which can upset their internal moisture balance, causing them to slowly die. Diatomaceous earth can do this because diatoms are spiky and their razor sharp tips can scratch the coatings, creating openings to allow moisture to migrate through. The diatoms also wreak havoc with their joints, like sand in a bearing. Boric acid can stick to their shells and feet, and they ingest it while cleaning themselves. Then it throws off their body chemistry, and slowly kills them.

If you prefer natural pesticides, I suggest looking at the JADAM Sulphur mix, combined with Ginko leaf solution. Sulphur is great because being elemental means the insects have no good way of developing resistance. I have the recipe somewhere.

I'm not 100% sure what scale insects you're referring to, but the most common ones in citruses where I live (Center of Portugal, where we call them "Cochonilhas" - more at https://acientistaagricola.pt/cochonilhas-aprenda-a-identifica-las-e-a-combate-las-com-receitas-naturais/ are usually sensitive to wind, so prunning the tree to open her up on the inside and allowing air and Sun to shine through as much as possible usually works like a charm.

My neighbors usually wash them with black soap, but I never have and just prunning (though sometimes a bit too much in my husband's opinion) has been doing the trick.
Just need to use all the prunnings as firewood or burn them, so it doesn't spread.

The ladybugs are a good idea too - I'm preparing to collect some and bring them into the property in Spring.

Hope you can solve the problem soon. And please keep us posted.

I have some cherry shrubs (Carmine) that are susceptible to scale, a least under my conditions. I first used horticultural oil (petroleum) diluted in water, which helped a pretty well. I got grossed out by the motor oil sensibility and I switched to vegetable oil (diluted), with similar outcome: not bad but it took a long time to work and scale kept coming back. Then I noticed the scale was migrating to my peach tree. This was serious!

I was tired of spraying with oil from a gallon sprayer, so on a whim, I put my garden hose on a hard spray and just hosed with water (during dormancy when the leaves were gone). That knocked off the scale really well and was instantly gratifying. And it was so simple and didn't seem to harm the bark.

It took care of the peach tree, but scale keeps coming back to the cherries annually, so they need to be sprayed periodically.  I too don't like fussy plants, so I cut down the cherries, thinking I'd plant Cornelian cherries (Cornus mas) instead. Didn't get around to it yet, and meanwhile, the old cherries sprouted up again (I coppiced without intending to!) and seem to stay clean of scale for a couple of years. Meanwhile birds have spread more cherry bushes throughout my yard, so my latest unintentional technique is to cut down the scale-infested ones, let the others grow til they get infested, and rotate.

Don't think coppicing would work for your citrus, but I highly recommend hard water spray. Simple, cheap, nontoxic.

My potted citrus doesn't get scale during the summer when they are outside. Once I bring them in, they always get an infestation within a couple of months. I use a fairly dilute Dr. Bronners soap (2 Tbsp in a quart). The peppermint soap works best for me. I coat every surface of the leaves and stems once a week or so and the scales die and come off in later treatments. I don't rinse off the soap, which I think is really important. I do maintenance every few weeks and it keeps them under control until the spring when they can go outside again.

Now that I think about it, when they are outside they get the benefit of winds and high pressure sprayer from the hose so that may be why they don't have a problem. The physical removal of the mobile form probably keeps them under control. All the predatory wasps are likely doing their part too.

[quote=Robin Katz]My potted citrus doesn't get scale during the summer when they are outside. Once I bring them in, they always get an infestation within a couple of months. [/quote]

My situation exactly!  I scrape large ones off with a thumbnail, gently on the leaves.  Then I spray with an organic product which seems to help.  Also I have used a cotton swab (Q-tip) dipped in rubbing alcohol to dot the ones on more sensitive plants.  The thing I hate about spraying is that my potted citrus are huge and difficult to move around, and since I have them near windows the overspray messes up my walls and woodwork where I can't easily get to wipe it off without a major pot-moving task.  I've tried the parasitic doobies but either they were damaged in shipping or just didn't like my scale bugs!  Ladybugs don't seem to care for the scale either, at least not the mature ones.

So, with all the chores I have as a caregiver and small homesteader, even in winter, my plants get what spray and scraping attention I can spare the time for.  My citrus always manage to come through the winter and breathe a sigh of relief when I wheel them back outside in late spring.  I did recently lose a little variegated cotton plant that I thought would be cool to try growing indoors - the scale migrated from my nearby meyer lemon tree, and the poor cotton plant couldn't handle it, got overrun and even after my triage attempts it didn't come back.

I also use soap. Dr Bronners, since it's easy to dissolve. It gets thicker as it dries, and smothers them. Then after a few hours or a day, I go after the scale insects with a water hose at the best pressure I can get. Works for me. Easier if your tree isn't tall, of course.

I get the scale on citrus trees, sapote trees and olive trees. To kill the scale I mix a Tablespoon of the green Palmolive dish soap with a quart of water in a spray bottle. I like the dish soap spray since I can get my hands in there to move branches around to spray everywhere. It works very good, the scale dries up in a week and dies.
I mention the "green" Palmolive because one time I used the pink Vitamin E enhanced Palmolive (since that was what was on the kitchen counter next to the sink) and all the leaves fell off the sapote tree in two weeks.    
To prevent a massive scale infestation you need to stop the ants from climbing the tree who then protect, groom, distribute, breed, tend and milk the scale for their Honeydew. Just like tiny dairy farmers tending their cattle! Use Tanglefoot painted around the trunk, but NOT ON the trunk since it will kill the bark. Wrap the trunk with a strip of plastic ( I use the plastic yellow CAUTION tape, if you are a cop use CRIME SCENE tape) to protect the bark. Use spackling or some kind of putty to fill the rough bark so the ants cannot crawl under your tape, then put the tape around the trunk over the spackling. Never put duct-tape on the bark, the glue will damage the bark which will take years to heal (I tried duct-tape once for grafting. Big mistake.). Then apply the Tanglefoot on top of the plastic.
Once the ants are no longer in your tree then the predator bugs will come in and eat the pest bugs like scale and aphids.

Despite the method you choose to control scale, unless you address the underlying cause you have not fixed the problem.

The top reason for aphid infestation is excess nitrogen. Something to keep in mind.

I've tried almost every method above, the only one that had efficacy was Neem cake (Neem oil I thought was worthless). This is on a commercial tea farm.

In my experience even if you don't see ants they are almost certainly involved.

Neem cake becomes a safe, systemic deterrent. Sprinkle a small amount of cake from trunk to dripline. Repeat when needed until no longer needed.

But I think it best to address the cause (s) than treat symptoms.

Soap with either lemon or orange oil kills all insects on contact. I use for everything now if no beneficial insects are present.

You mention the spray from the shop was citrus based but in all honesty perhaps they didn't make it strong enough because I can't think of a time it hasn't worked. I have even used it on scale on a lemon tree etc.

My "go-to" for organic control is Diatomaceous Earth. We always have it around for the animals and even us humans so ...  You can just add some (1/2-1 cup per gallon of water) into your soap solutions that others have suggested, or you can dust the plants with it (I have a Dustin-Mizer that I use) for larger applications.

Sprays rarely work on scale because you need to time it exactly right... they are only vulnerable to sprays during a short time in their lifecycle when they are crawlers, just after hatching. They crawl to their new location and stay put and build a waxy coating to protect them. You'll need to manually remove, which it seems you are already doing. I dip a Q-tip in rubbing alcohol and rub them all off. You'll go through a bunch of Q-tips. You'll have to repeat this procedure every few days until you break the cycle (as others have mentioned).

The citrus leaves are thick enough to withstand the alcohol and the rubbing. You definitely do not want to coppice your citrus. Citrus are good as potted plants because they keep most of their energy above ground and therefore do better than most trees with a restricted root area. Plus, most citrus are grafted on rootstock which you don't want to start sprouting. If you do prune your tree, don't take more that 25% - 30% off.

Scale usually take over when the tree is stressed. They need lots of sun and regular water but wait until the top inch of soil is dry to soak it, and make sure it can drain so it's not sitting in water. They also are high iron and nitrogen feeders because most of their energy is stored in the leaves. Good luck. Hope this helps!

Hi Ann, and welcome to permies! That's a good point to know about citrus investing mostly in their above-ground assets. I've managed to move a productive lime tree by carefully lifting and preserving as much of the root mass as I could. I was actually surprised at how much was there and its extent...a relatively small tree, less than 2m tall, had more going on under the surface than I expected. But it survived the move and even though its new location might not be quite as cushy as the original spot, it's loaded with fruit. And no scale. Meanwhile, in another corner of the garden the lemon always has lots of whitefly and occasional outbreaks of scale. I spray it with the hose if it gets annoying, but the ants go into overtime.

I ended up with some scale and ants tending them.  I made a white oil spray which did the trick.  Thought that they were still alive until I was able to wipe the dried shells off.  This is a deterrent to the ants as well as the oil is sticky
1/4 cup of good vegetable oil such as olive oil or bran oil
2 Tablespoons of liquid soap
2 cups water.
Put in a bottle and shake.  It will turn white.
Make sure that the soap is a natural type and not bleach or detergent liquids.

Spray on the plants, particularly under the leaves and down to the base.  Or wipe the plants with a soft rag.
Make enough for a week or two because it goes off.
Works on  mealy bugs as well

My schizandra vines are getting some scale and I considering spraying with a white oil as described above. Then the other day I noticed a little black lady bug with an orange spot on each wing that seemed to be eagerly enjoying (ie consuming) the scales. I looked it up and sure enough, it seems to be a twice-stabbed ladybug (Chilocorus stigma), which eats aphids and scale, including pine needle scale, beech bark scale, and Florida red scale. Apparently it lives in North America east of the Sierra Nevadas. Somehow it found its way to my plants when they needed it. The scale is looking better, so there are probably a family or more hiding around my garden. Wikipedia says they aren't sold commercially, but maybe planting flowers they like around your citrus trees could help attract them.

https://en.wikipedia.org/wiki/Chilocorus_stigma

https://www.treehugger.com/how-to-attract-ladybugs-to-your-garden-4863669

Sarah Bassan-Zehavi wrote:Try taking a close look at the immediate environment of the tree - what is making it weak and thus a target for infestation

I am wondering if inadequate lighting could be the cause. There are established studies showing excess nitrogen makes plants weak and more susceptible to pests. Although it's more commonly found in over application of inorganic Nitrogen fertilizers, when a healthy plant is moved indoors for overwintering, lower light level reduces photosynthesis and causes relatively high nitrogen to build up. Being natural predators are not available, the pest pressure could increase quickly.

For example, I brought in some stonecrop shoots from outside to root in water. The ones sitting in a shady window sill showed stem elongation and had many aphids within a week. The others with bright indirect sun rooted fine without any pests. Since they were both in water, I am feeling the reduction in sugar content leading to excess nitrogen is making the difference.

So maybe giving the citrus tree additional light would help?

Any other solutions?

I've tried the lot and um, the scale bugs are winning.  

I don't remember whether you tried rubbing alcohol. I've had some luck with that on indoor plants with persistent scale problems.

Phil Stevens wrote:I don't remember whether you tried rubbing alcohol. I've had some luck with that on indoor plants with persistent scale problems.

I've been using alcohol on a swab to wipe off the scale, but they multiply faster than half an hour a day can remove.  

Spray without mixing and the leaves die.

spray mixed with soap and water hasn't had a great effect on this plant.

Is there another way to use alcohol for my scale bug genocidal plans?  

I'm pretty sure it was drugstore grade 70% isopropyl and I just sprayed directly on the branches. This was on a ficus, which was pretty tough. If the citrus trees don't have any tender new growth you can do a 50/50 dilution without harming the plants, but it might burn fresh shoots.

Spraying, whether it's with alcohol, soap, or neem, gets the small ones that are mobile and searching for a spot to clamp on, and it works by dessicating them before they've had a chance to grow a protective covering. They're just about invisible to the naked eye.

Ladybugs are voracious scale predators, but getting a hold of those in the winter might be difficult.

I tried catching ladybugs that got into the house, and putting them on my citrus trees infested with scale.  For some reason they didn't stay and eat the scale.  

Alcohol works OK but is labor-intensive as r has discovered!  I use an organic commercial spray which reduces them significantly... for awhile.  Then back they come.  it's virtually impossible to get every. single. one. so they will eventually make themselves known again once they multiply again.

I learned how they migrate from potted plant to potted plant:  the males can fly!  They don't kill my citrus trees as long as I spray or scrape them off or use alcohol once in awhile, but I've just lost a jiaogulan tea plant (immortality herb) that was just too delicate to handle the scale plus the "remedies" after about 3 years of fighting it.  Some plants just really attract scale.  Same with spider mites.  My citrus get those too, which i can control but never seem to eradicate.  I've set up an isolation room this winter for my citrus trees, and my aloe plants which appear immune to scale and spider mites, and a poor little spilanthes plant that succumbed quickly to the spider mites just from being near a citrus tree during the summer.  I sprayed it well but it hasn't come back to life yet.  It too is rather delicate.  

Sadly, the only true "cure" is to destroy all your infested plants, sterilize the pots, wait awhile to be sure anything hanging around in the room had died off, then start over again.  And probably do that every 3-4 years if you put your plants outside during the summer.  I've tried buying predator bugs and introducing them, but that hasn't completely handled the issue either, only reduced it for awhile.  Then the predators die off when not many scale or spider mites or thrips are left, leaving just enough of the pests to eventually repopulate the plants.

Sigh...  I guess that's what we get for trying to grow things outside their native zones!  I haven't tried putting electroculture antennae in these plants yet, too much else more urgent/important to do, but maybe I'll get around to it this winter and see if that helps at all.