The aloe mite, Aceria aloinis Keifer, is a microscopic eriophyid mite that causes disfiguring gall-like growths on aloes and related succulents — a condition widely known among growers as “aloe cancer.” Unlike mealybugs, scale insects or spider mites, which are visible to the naked eye and attack the surface of the plant, aloe mites are invisible without magnification, live hidden inside the tissues of their host, and cause permanent, irreversible damage to every structure they infest. There is no cure for the galls themselves — they will not regress even after the mites are killed. For this reason, the aloe mite is considered the single most destructive pest of cultivated aloes worldwide. This article provides a comprehensive guide to the biology, identification, treatment and prevention of Aceria aloinis, based on the published scientific literature and decades of practical experience from specialist growers.
What is the aloe mite?
Classification
Aceria aloinis belongs to the family Eriophyidae, a vast group of gall-inducing mites within the class Arachnida (the same class as spiders, ticks and scorpions). More than three thousand species of eriophyid mites have been described, and most are highly host-specific. Aceria aloinis feeds almost exclusively on species of Aloe (Asphodelaceae), though it has also been reported on closely related genera including Gasteria, Haworthia and Haworthiopsis. A Dave’s Garden contributor has reported infestation on Agave, though this appears to be rare.
Morphology
Eriophyid mites are extraordinary among arachnids. They are vermiform (worm-shaped) — elongate, cylindrical, resembling a microscopic sausage — and possess only four legs instead of the eight typical of most arachnids. Adults measure approximately 0.1 to 0.2 mm in length. They are completely invisible to the naked eye and require at least 10x magnification to detect on a skin scraping of infested tissue. The Dave’s Garden contributor palmbob describes finding them under a microscope after performing a scraping technique similar to that used in veterinary dermatology for mange mites.
Biology and life cycle
The aloe mite lives, feeds and reproduces entirely within the tissues of its host plant. It feeds on epidermal cells, and during feeding, it injects a chemical — a growth-hormone regulator — that causes the plant’s normal growth pattern to become chaotic and disorganised, producing the characteristic galls. The galls then grow around the mites, effectively encasing them in a protective structure where they continue to feed and lay eggs.
Reproduction is prolific: Debra Lee Baldwin reports that each female can lay approximately 80 eggs per month, and as many as eight generations can be produced per year. This means that a single founding female, if undetected, can produce a massive infestation within a few months.
Dispersal is primarily by wind. The mites are poor crawlers (with only four tiny legs on an already tiny body) but light enough to be carried on air currents from one plant to another. They are also spread by contact — on gardening tools, on clothing, on the hands of people who handle infested plants, and critically, by pollinators (sunbirds, bees, butterflies) visiting infested flowers and carrying mites to the next plant.
Origin and history
Aceria aloinis is thought to have originated in South Africa, where it coevolved with wild aloe populations. It was first identified and described scientifically in California by the American entomologist Hartford Keifer in 1941, in a California Department of Agriculture Bulletin titled Eriophyid studies XI. Keifer named it Eriophyes aloinis (later reclassified as Aceria aloinis in 1952). San Marcos Growers notes that it was found on aloe plants in Los Angeles County (North Hollywood) and San Diego County (Pacific Beach) in 1940, and in Santa Barbara in 1941 — likely introduced through zoos or botanical gardens importing infested South African aloes.
The first mention in a horticultural journal appears to be a 1984 article by Charlie Glass and Bob Foster in the Cactus and Succulent Society of America Journal, which warned that “too many aloe growers diagnose this problem as an interesting malformation related to crests, whereas actually it is the external manifestation of a serious disease.”
Today, the aloe mite is established wherever aloes are grown outdoors in warm climates: throughout California, the Mediterranean basin, Australia, and of course southern Africa.
How to identify aloe mite damage
The fundamental problem: invisible pest, visible damage
The aloe mite itself is never visible on the plant without a microscope. Identification depends entirely on recognising the galls — which is the damage, not the pest. By the time galls are visible, the infestation is already established and the damage is irreversible. This is the central challenge of managing this pest.
Early signs
The earliest signs of infestation are subtle and easily missed by inexperienced growers. Trex Plants describes the first symptom as a leaf edge that looks “almost dirty, with no tooth serration” — a slight blurring or irregularity of the normally clean, toothed leaf margin near the growing centre. At this stage, the galls have not yet formed but the mites are already feeding and injecting their growth-altering chemicals.
Other early signs include slight distortion or swelling at the base of new leaves, and unusually lumpy or deformed emerging flower buds.
Fully developed galls
Once established, the galls are unmistakable. They appear as clusters of warty, tumorous, blister-like growths — dense masses of fleshy, spindle-shaped projections that erupt from the leaf surfaces, leaf axils, stems, and especially from inflorescences. The galls are typically greenish at first (matching the host tissue), later turning brownish as they age.
Galls can appear anywhere on the plant but are most commonly found at the growing tips (meristems) of leaf rosettes and on flower stalks. This is because the mites are attracted to the most actively dividing tissues. The flower stalks are often the most severely and earliest infected part of the plant — and this is also the primary route of dispersal, as pollinators visiting a galled inflorescence carry mites to the next flower.
Dave’s Garden contributor palmbob describes the galls evocatively: “the mites secrete a chemical substance while feeding that alters the normal growth pattern of the tissues, causing them to grow haphazardly and bizarrely, a lot like the way many cancers grow in people and animals.”
Key distinction: galls are permanent
Even after the mites are killed — whether by chemical treatment, physical removal of tissue, or natural death — the galls themselves are permanent. They will not regress. The deformed tissue will remain deformed for the life of the leaf or structure. This is fundamentally different from damage caused by mealybugs, scale or spider mites, which can resolve once the pest is eliminated.
Which aloe species are most susceptible?
Not all aloes are equally vulnerable. Grower experience in California and South Africa has identified certain species and hybrids as particularly susceptible, while others appear more resistant.
Highly susceptible species
Aloe x spinosissima — San Marcos Growers describes this hybrid as one of the plants they monitor “continuously” for aloe mite and notes that its attractiveness to the mite was a significant concern for continued production.
Aloidendron barberae — Agaveville contributor palmbob reports that the giant tree aloe is “one of the more sensitive aloes” to aloe mite, though infestation does not usually kill the plant.
Aloidendron tongaense — Garden Aloes describes it as a “huge aloe mite magnet.”
Aloe maculata (soap aloe) — very commonly infested in California landscapes.
Aloe marlothii — palmbob describes “very cancer-like tumors on stem” in his own collection.
Aloe greatheadii — palmbob reports early flower changes from mite infestation.
Aloe hybrids sold in mass retail (Altman Plants and similar) — Dave’s Garden contributor reports that these are often a vector for the pest entering new collections.
Apparently more resistant genera
Haworthia and Haworthiopsis — palmbob notes that despite growing many specimens in close proximity to infested aloes, he has not seen infection on these genera. However, Artisan Plants reports that mites are “now capable of infecting Haworthia plants,” and the scientific literature (Smith Meyer 1996, Deinhart 2011) confirms that Gasteria and Haworthia can be hosts.
Gasteria — similarly reported as less frequently affected, but not immune.
The general trend is that large, outdoor, landscape-scale aloes are the most commonly and severely infested — particularly those with accessible flower stalks visited by pollinators — while small, indoor-grown succulents are at much lower risk (but not zero risk, as mites can arrive on new purchases).
Treatment
Step 1: physical removal (always first)
The most important and most effective intervention is immediate physical removal of all infested tissue, followed by disposal in sealed trash bags (never in compost or green waste). This is the consensus recommendation of every authoritative source — San Marcos Growers, Debra Lee Baldwin, World of Succulents, Trex Plants.
The protocol is straightforward: using a sharp, clean knife or pruning shears, cut well below the visible gall — at least several centimetres into apparently healthy tissue. The mites may be present in tissue that looks normal, so generous margins are essential. Seal the excised material in a plastic bag and dispose of it in household waste. Sterilise your tools with rubbing alcohol after each cut.
After excision, dust the cut surfaces with sulphur powder or cinnamon — both have mild antimicrobial properties that help protect the wound from secondary infection.
Monitor the plant closely over the following weeks. If new deformed growth appears from the cut site, the mites were not fully removed and the treatment must be repeated or the plant destroyed.
For severely infested plants (galls covering more than one-third of the plant), the most practical and responsible advice is to destroy the entire plant. As the Kelly Griffin community of aloe hybridisers puts it: “It might be smart to consider not spending twenty dollars on poison for a ten dollar plant.” Keeping a heavily infested plant in a collection risks the entire collection.
Step 2: chemical treatment (after physical removal)
Chemical treatment alone is not effective — this is the critical lesson from the scientific literature. The study by Villavicencio et al. (2014, Journal of Economic Entomology 107: 2088–2094) tested nine miticides on infested Aloe reitzii without gall removal. Although the miticides killed the mites, they did not reduce the visible damage because the galls continued to grow from tissues already chemically altered by the mites. Only when gall removal was combined with miticide application did the researchers achieve marketable plants.
The three modes of action identified in the study as effective are:
Contact miticide: carbaryl. Carbaryl (sold under the brand name Sevin) is an inexpensive, widely available insecticide that has been effective against aloe mites in multiple studies and anecdotal reports. Important note: around 2018, the Sevin brand changed its active ingredient from carbaryl to zeta-cypermethrin (a pyrethroid). Growers report that the new formulation does not work against aloe mites. If using carbaryl, ensure the product label confirms carbaryl as the active ingredient.
Translaminar miticide: spiromesifen. Spiromesifen (trade name Oberon) penetrates the leaf surface and kills mites within the tissue, not just on contact. The Villavicencio study found this to be the most effective single treatment in reducing damage severity.
Systemic miticide: spirotetramat. Spirotetramat (trade name Movento) is taken up through the roots and distributed throughout the plant. As a systemic, it can reach mites hidden deep within the meristematic tissue. This is the most promising option for preventive treatment of valuable specimens.
Additional notes from grower experience:
Abamectin (trade name Avid/Agri-Mek) is reported effective at killing mites but is not curative of galls. Most useful as a preventive.
Imidacloprid (a neonicotinoid) is not recommended for aloe mite — at least one experienced US grower reports that it may actually worsen infestations, possibly by eliminating predatory arthropods that suppress mite populations.
Step 3: continued monitoring
After treatment, monitor the plant intensively — at least weekly — for two to three months. Because the mites live at meristem-leaf junctions deep inside the plant, symptoms will continue to emerge and may worsen before they improve, even if the mites are dead. New, clean growth from the centre of the rosette, without distortion, is the first sign of successful treatment.
Prevention
Prevention is far more effective than treatment. The following measures, applied consistently, can protect a collection indefinitely.
Quarantine all new acquisitions
Every new aloe entering your collection should be isolated from existing plants for at least four to six weeks before being placed among your other aloes. Inspect new acquisitions carefully — especially the leaf bases, the growing centre, and any developing flower buds — for any sign of irregular growth. Mass-produced aloes from large retail outlets are the most common vector of introduction.
Regular inspection
Walk your collection regularly and inspect every plant up close. Monthly inspection is a minimum; weekly is better for outdoor collections in endemic areas (California, Mediterranean coast, coastal Australia). The earlier an infestation is detected, the higher the chance of saving the plant.
Manage inflorescences carefully
Because flower stalks are the primary dispersal route (via pollinators), consider removing developing inflorescences from aloes growing near known infested populations. This eliminates the pollinator-mediated pathway.
Preventive systemic treatment
For irreplaceable or high-value specimens, a preventive application of a systemic miticide (spirotetramat or abamectin) before any sign of infestation can provide a window of protection. This must be applied before the mites arrive — once galls are present, a systemic will kill the mites but not reverse the damage.
Avoid wind-borne transmission
If neighbouring gardens have infested aloes, physical barriers (walls, dense hedging) can reduce wind-borne dispersal, though they cannot eliminate it entirely.
Never compost infested material
All removed galls and destroyed plants must be sealed in plastic bags and placed in household waste. Never add infested material to compost, green waste or garden clippings.
Frequently asked questions
Can aloe mite kill my plant?
Rarely directly. The mites themselves do not kill the plant — they cause disfigurement. However, severe infestations weaken the plant by disrupting photosynthesis and growth, making it vulnerable to secondary infections (rot, bacterial disease) that can be fatal.
Can aloe mite spread to my indoor collection?
The risk is much lower indoors than outdoors, but not zero. Mites can arrive on new purchases from nurseries or online sellers. Quarantine is the best protection.
Is aloe mite contagious between plants?
Yes. The mites spread by wind, by contact (tools, hands, clothing), and by pollinators. An infested plant is a breeding ground that puts every aloe within wind-dispersal range at risk.
Does rubbing alcohol kill aloe mites?
Isopropyl alcohol can kill mites on contact but has no residual effect — it only works on the mites it physically touches. Since most mites are hidden deep within gall tissue, alcohol is not a practical primary treatment. It is useful for sterilising tools after surgery.
Are some aloes immune to aloe mite?
No aloe species has been documented as completely immune. However, susceptibility varies enormously. Small, slow-growing, indoor-cultivated species are rarely affected. Large, landscape-scale, outdoor aloes with accessible flowers are the most common targets.
References
Keifer, H.H. (1941). Eriophyid studies XI. California Department of Agriculture Bulletin 30: 240–244.
Keifer, H.H. (1952). The Eriophyid mites of California. Bulletin of the California Insect Survey 2(1): 1–123.
Villavicencio, L.E., Bethke, J.A., Dahlke, B., Vander Mey, B. & Corkidi, L. (2014). Curative and preventive control of Aceria aloinis (Acari: Eriophyidae) in Southern California. Journal of Economic Entomology 107(6): 2088–2094. DOI: 10.1603/EC14234
Deinhart, N. (2011). Tiny Monsters: Aceria aloinis. Cactus and Succulent Journal 83(3): 120–122. DOI: 10.2985/0007-9367-83.3.120
Smith Meyer, M.K.P. (1996). Mite pests and their predators on cultivated plants in Southern Africa — Vegetables and berries. ARC Plant Protection Research Institute.
Glass, C. & Foster, R. (1984). The ABCs of Cacti and Succulents. Cactus and Succulent Society of America Journal 56(4).
San Marcos Growers (2005, updated 2022). Aloe Mite. https://www.smgrowers.com/info/aloemite.asp