Ahhh, aloe mites. The bane of most aloe growers’ existence. If you’ve been diligently collecting your aloes for years, growing several in the ground for those giant trees, the last thing you want to see is one of those little cancerous looking lumps. While they won’t actively kill your aloes, they’re extremely unsightly, especially in later stages as they develop some size.
Despite being a pest, which you would think makes them obviously and objectively bad, they can be a touch controversial.
Eh, maybe controversial is the wrong word. Touchy? Confusing? Divisive. They can be surprisingly divisive. I’ll get into some of the reasons why as I go through this post, but first, a great big disclaimer:
I’m not a scientist. I’m not a professional horticulturist. I’m not a chemist. My recommendations are just that, recommendations, and they’re based on my experience, what I’ve been able to learn from research, and from what I’ve been fortunate enough to talk to other growers about. There’s no single right or wrong approach or stance to take when it comes to Aloe Mites. Based on your own knowledge, risk acceptance, and ability to treat them, you can determine what you’re okay with (or not!).
What is Aloe Mite, anyway?
Also known as Aloe Cancer, Aloe Gall, Aloe Warts, or simply “the fucking worst”, aloe mites are microscopic little buggies that live exclusively in aloes (shocker, I know).
The latin name for the species is Aceria aloinis, and are an absolute plague for us here in California. While thought to originate in South Africa, it was first identified and named here in Southern California. San Marcos Growers has a great little discussion of the early description and naming, but simply put: it was spotted in the very early 1940s in LA, San Diego, and Santa Barbara – likely related to zoos or gardens importing infected South African aloes.
Aloe Mite showing up as a deformed growth on an Aloe “Purple Haze” hybrid
You can’t exactly be upset at the zoos or horticultural gardens who introduced this pest to us, though. The thing about Aloe Mite is that it’s a truly microscopic pest, one that resides, hidden, in the flesh of the plants. Sometimes it’s invisible for only a few months, sometimes it’s invisible for years.
The distinctive looking malformations on the plant are galls that are formed by the pest. These galls hide the mites, where they exist in relatively large numbers, and where they reproduce. In some aloe species, the first time you’ll spot them is on a bloom stalk, creating a montrose looking lump instead of a proper pretty cone of flowers. It’s thought this is one of the ways the mites spread; birds and bees and butterflies all pollinate aloes, and by drinking from a mite-infested bloom stalk, they carry the mites from one plant to another.
Regardless of how exactly they spread, the fact is: if your aloes are outdoors, they’re at risk. The more infested other plants are in your neighborhood, the more likely it is that your own aloes are going to catch the mite, despite your best efforts.
Let’s start with how to identify the little pests before we move into how to manage them.
Identifying Aloe Mite
I assume that you, like me, want to know how to spot the dreaded pest before it spreads throughout your entire aloe collection.
Some aloe species and some hybrids seem far more prone to displaying their infection early compared to other species.
At left is an Aloe striata hybrid, an attractive landscape plant with no spines on the leaves and beautiful blue flesh color with red margins.
It’s also extremely susceptible to Aloe Mite. I’m in an area where many of my neighbors have aloe mite, and it’s quite common outdoors, and I’ve never had one of these landscape varieties last more than 2 or 3 years before getting galls like this one. The galls grow in size extremely rapidly, too, from a little blemish to a full blown tumor in under 6 months (like the one at left).
At first glance, both of the plants below seem healthy, happy, and gall-free. They’re large, they’re established, they’re beautiful in-ground landscape specimens that I’ve had in the ground for over 4 years.
Sadly, both have aloe mite – but both are early enough that they are treatable.
Plant above was purchased as Aloe vryheidensis in January of 2020, and has been in ground since then
Aloe thraskii, purchased from a friend back in 2016 as a seedling, has been in ground since 2018. Started blooming in 2022.
How do I know these plants both have aloe mite?
Like an obsessed weirdo, I stare at them up close on a regular basis. At least once a month, usually much more often. I walk around the property regularly, and check on my rarer species or favorites even more often. A little bit of aloe mite gall that appears can, and will, very rapidly become a large and unsightly growth.
The Aloe vryheidensis, when I get up close, has the first signs of aloe mite showing up at a leaf edge near the center of the plant. This is most often where you’ll see it pop up, especially on tree-like species.
This is a far more subtle sign of aloe mite recurring in this Aloe thraskii – I treated it for the first time 3 years ago, so I knew what to look for. The edge looking…almost dirty, with no tooth serration, is an early sign.
Lower down on the Aloe thraskii, the leaf edges are healthy and look normal. If I didn’t check the entire plant closely, I wouldn’t know there were mite bolls starting to emerge in the newest growth on the plant.
While the edges closest to the trunk are smoother here, with little to no serration or teeth visible, you can see the clean white-green edges. There’s even sign of a tooth or two, just widely spaced out.
The important thing is seeing the crisp, clean edge compared to the mite coming in above. Keeping up on application of a preventative pesticide in this plant would keep it looking pristine like this.
I say keeping up on a preventative pesticide because, as I alluded to earlier, I’ve already treated this plant for aloe mite once. It’s my “case study” for treatment, and also the warning. So…let’s talk treatment!
Treating Aloe Mite
Before we get into treatment, a comment:
You can’t completely cure aloe mite. You prevent it from emerging, and you manage it when it does. There’s a reason many collectors see it in their collections and simply toss any plants showing signs of the dreaded mite.
Can you treat aloe mite with organic or natural methods?
Sure. Throw the plant away.
That’s it. There is no natural cure for aloe mites. If there’s a predator that eats them, it hasn’t been documented or studied yet. Aloe mites live within the flesh of the plant, so unless there’s a predator getting into the skin and flesh of the aloe – it’s not going to eat aloe mite.
Treating aloe mite requires chemical warfare, plain and simple. If you don’t want to use chemicals to combat aloe mite, you’ll just keep seeing it, or you’ll need to throw away any plants that show signs of the mite.
Step 1 to treat Aloe Mite
First, you need to trim off any visible sign of aloe mite. Use a clean, fresh razor blade, and slice away.
At right is my Aloe thraskii in 2021, when I first treated it for aloe mite. You can see the infected flesh close to the stem of the plant, and that’s what you should be slicing away.
Slice with a heavy hand! The visible aloe galls will never go away, never get better, and never get smaller. They are dense concentrations of the mite (as far as I know), and one of the best ways to reduce the infection to a manageable level is to simply cut out the infected tissue.
Should you use cinnamon or a a topical powder on the cuts?
I didn’t, and I don’t think you really need to if you’re treating your aloes in the spring or summer, when the weather is best.
I’m in an ideal climate for aloes, so I can trim and slice and dice just about any time of year I’m not expecting a frost. When cutting your plants at home, use your judgement; you should have several days of clear, sunny weather, somewhere well ventilated to keep them, and if at all possible, it should be outdoors with mild weather that’s not any cooler than 50F.
All of that is just to give the plant the best chance at callousing over the cuts, scarring well, and preventing any rot from setting in. You may need to spray a pesticide on the aloe as well, to keep opportunistic pests deterred from taking advantage of an easy meal.
For my Aloe thraskii, I had to cut back pretty drastically. In order to cut away all the infected tissue, it detached almost the entire leaf from the plant, so I simply removed leaves where I saw that occurring.
Earlier, I referenced knowing when my Aloe thraskii was showing signs of emerging aloe mite: this process was how I learned what it looks like in its earliest stages.
See the “dirty” looking edge at left? That’s aloe mite and had to be cut off.
You can see that quite a few leaves were cut away. You will likely need to do the same! If you have a healthy aloe that’s growing in a compact, stacked form…the mite can be hiding very effectively next to the plant stem. Take your time and be ruthless with your cuts!
With this tree aloe, I cut a lot of leaves off, leaving it looking rather bedraggled and lopsided.
The aloe mite only showed itself in the middle growth of the plant, and I was able to effectively cut it out and cut off quite a few leaves.
It looked quite sad that first year, but rebounded quickly! And for a landscape plant that will last decades, a few months of looking rough are worth the effort to keep a plant that is highly sentimental to me.
Step 2 to treating Aloe Mite
You can’t just cut away the aloe mite and expect it to stay away. If you’re looking for a chemical-free way to treat aloe mite, step 1 is your first step to try and preserve your prized plants.
If you keep seeing the bolls appear and you don’t want to use chemicals, your only other option is to simply throw away the aloe. The mites will not go away; as I’ve said, they’re in the flesh of the plant. If your aloe is alive, so are the mites. They’re effective survivors!
However, if you do want to use chemicals, your options are slim.
Aloe mite is exceptionally resistant to nearly all pesticides.
There have been some studies on aloe mite, but the publicly available study was funded by commercial growers. The goal of the study was to identify pesticides and management methods that keep plants looking attractive for sale, NOT to eradicate the mite. The study – linked for you here – identified a lot of extremely helpful information! But it’s important to note that it was focused on keeping plants looking attractive for sale, and at scale.
Effective Pesticides for Aloe Mite
Hahaha, effective pesticides.
If you’re in California, like me, you have one option: Kontos.
It is not cheap. I’ve linked it for you here – it’s honestly prohibitively expensive if you only have one or two plants. As you get into growing dozens, or hundreds, of plants, it starts being worth it to invest in the equivalent of nuclear warfare against pests.
You cannot purchase it in Florida, Kansas, or Puerto Rico. In California (like me) and Washington, there’s specific formulas for our regulatory requirements.
Aloe gall under a simple computer-connected microscope; not a close enough resolution to see the mites. Shows the discolored skin and lumps.
If you’re checking that research paper I linked above, the active chemical in Kontos is Spirotetramat at 22.4%. It’s alarmingly toxic, and you should wear protection in the form of goggles, a face mask, and long sleeves/pants when spraying. It’s not a great chemical, and that’s probably why it’s expensive and restricted.
I keep our dogs indoors for at least 4 hours, and the chickens stay in their coops for at least 24 hours after I spray.
It’s a systemic pesticide, so you want to spray it in the early morning or, even better, in the early evening as the sun goes down so the plant absorbs as much as possible. You can also dredge the soil, which is helpful for potted plants, but requires a considerable amount of treatment for in-ground and larger aloes. I didn’t dredge my Aloe thraskii with a dedicated treatment, but after spraying plants, I’d rinse the sprayer and then dump that and any excess at the base of the aloe.
Healthy aloe tissue; still not a close enough microscope resolution to see the mites themselves but you can clearly see how different the healthy tissue looks from the mite-infested tissue.
When you first cut your aloe, immediately spray with the Kontos within 24 hours, preferably the evening of the same day.
If you’re not in California, you can alternatively use Sevin concentrate with carbaryl, which is one of the other effective chemicals identified in the study. It’s also significantly more affordable, available in a dust form that helps treat grubs, and is actually ideal when paired with a systemic treatment.
Other chemicals identified effective in the study include fenpyroximate and spiromesifen, but I couldn’t reliably find commercially available pesticides that included those in their active ingredients.
How often should you keep treating your aloes?
I was following a schedule of twice a year with my Kontos applications; once in late fall, when any risk of heat waves was probably past, and then again in late spring, before the summer heat really hits.
It’s very similar to my schedule for a residual pesticide, which I aim to apply at the start of the dormancy period for many of my cacti, and then again as they start to wake up for the year.
The same Aloe thraskii in December of 2023, showing happy, healthy new growth.
The difference between 2023 and 2024?
This year, I was a little late applying my Kontos – I usually spray everything in early October, but it’s been a very hot fall for us. I didn’t want to risk scorching my cacti, and have delayed the application.
Whomp whomp, the mites are appearing.
I’ve also seen several of my other, less prized landscape aloes showing significant signs of mite infestation with big galls, indicating I need to go through the yard to remove the less costly specimens.
Can I prevent Aloe Mite from occurring in my collection?
If you’re in Southern California and your aloes are outdoors, it’s simply a matter of time. If you see infected plants within walking distance of your house, your aloes are at risk.
Any aloes you get from a big box store are almost guaranteed to be infected, and for those, it is also often just a matter of time. The gorgeous star aloe hybrids we all love are grown in the exact nursery conditions described in the study, where the goal is to keep as many plants as possible at an infestation level that keeps them suitable for sale.
If you’re collecting hybrids, honestly, you can’t escape the mite. It’s there. Anyone (including me!) growing their aloes and dividing their named hybrids is growing them in an area that is exposed to aloe mite.
Can you reduce the risk? Yes, significantly.
Some species, and some hybrids, are much less susceptible to the mite than others. My Aloe vaombe garden hybrids have grown next to highly infested aloes from garden centers for years, and have never shown a blemish. Some Home Depot hybrids (like Aloe “Oik”) seem to rarely, if ever, show sign of the mite. I’ve never seen it on one of my Aloe “AJR”, or many of my less common hybrids, like the “Intense”.
I do see it often on large landscape specimens, and it seems oddly common on the “mauna” family – Mauna Loa, Mauna Kea, etc.
There’s no guarantee as to which hybrids, which plants, or which species will for sure get the mite and show signs of infestation. Apart from how attached you are to a given plant, that is. I swear it’s a rule that if you really love a given specimen, that is for sure the one that’s going to show signs of the mite in a matter of weeks.
Is aloe mite a bad thing?
Should we be upset about nurseries simply trying to manage the pest, rather than eradicate it? Is it problematic that it’s likely spreading all over the US thanks to big box stores and nursery distribution?
Ehhh…maybe. We don’t know enough about it to say either way.
We do know that it is almost entirely a cosmetic issue. It makes the aloes ugly. As collectors, this is antithetical to our existence. We despise this.
Does it truly hurt the plant? Does the plant suffer for the mite?
A bit, it seems, but eyeing some of the enormous landscape aloes showing extreme amounts of aloe mite infestation, it sure doesn’t seem to stop them from growing, blooming, or otherwise reproducing. It’s just part of their lives, and they’re just less attractive to our human eyes.
Should you toss out your infested plants? Cut them up and treat them with chemicals? Leave them be and hope for the best?
The answers to those questions are your own.
The best I can do is be honest that I live in an aloe mite infested area. I treat for them, and don’t sell plants showing signs of gall. But can I ever guarantee that any aloe I sell isn’t infected with aloe mite?
Nope.
Neither can anyone else in California. We can make our best effort, and that often is more than enough. Preventative measures, especially for seed grown specimens, go a long way.
But they’re always out there.
And if that’s not the perfect horrifying thought for a Halloween-season post, I don’t know what is.
You’re welcome for the nightmares.
