When a succulent isn't looking quite right, you may wonder if you've done something wrong. Here's what to look for: symptoms, causes, severity, prevention, and treatments for common succulent pests and problems.
- Not Serious but unsightly.
- Plants eventually outgrow it.
Aeoniums are especially prone to brown marks from being handled. Lines and blotches show up a day after something or someone has touched the leaves. If you're making a bouquet of aeoniums or taking cuttings, hold them by their stems only, and don't let them brush up against anything.
See my video: Aeonium Leaves, What You Need to Know (1:23).
- Not serious but unsightly.
- Plants eventually outgrow it.
Blotchy patches appear on leaves and the top layer sloughs away. Unlike sunburn, the damaged area is lower than the surrounding leaf surface. Unlike frost, which typically "burns" tips, edema shows on the wider part of the leaves.
Edema can happen when agaves that are used to a cool, mild climate like the Bay Area's go through an intense heat spell.
Inconsistent watering also can cause edema. Blistering on one of my agaves happened after a pipe broke beneath it. If there's a way to anticipate or prevent the damage, I'm unaware of it.
Agave Grease Mite
- Serious and unsightly
Dark, greasy blotches on agaves result from an eriophyid mite infestation, which can spread to your other agaves. It's best to remove and destroy the plants, but if this isn't possible, experts recommend drenching affected agaves (and those nearby) monthly, during the spring-fall growth season, with miticides, alternating two or three. Those that are earth-friendly include Neem Oil and GrowSafe. Continue treatment until new leaves show no sign of disease---which may take up to a year.
Agave Snout Weevil
- Serious, potentially fatal
- Prevention is essential: Drench the ground beneath agaves in your garden in spring and fall with systemic insecticide.
If your agave wilts and has dark patches at leaf axils, it likely has snout weevil, a thumbnail-sized black beetle that punctures an agave's core and inserts its eggs. Grubs hatch, consume the core of the plant, turn it to mush, then tunnel into the ground to pupate.
For detailed info on this rapidly spreading pest, see my video, "Agave Snout Weevil Prevention and Treatment" and read my online article.
- Serious because it spreads
- Disfigures the plants
A microscopic mite causes bubbly, tumorlike growth on aloes, especially along leaf margins and flower spikes, and where leaves meet the stem. Once in a plant’s tissues, the mite continues to cause cancerous growth. Discard the aloe unless it's important to you to keep it, in which case, cut out any affected tissue and bag it for the trash. Sterilize the tools you use with bleach or isopropyl alcohol. Aloe mite is still going to show up on that particular plant, so even if it looks fine, don't give friends cuttings.
More: How to Manage Aloe Mite.
- Plants recover if caught in time.
Ants nest in the soil beneath aloes, haworthias and gasterias in late summer and fall, and feed on the plant's core, which fills with dirt as the pests push it up from below. Peel away damaged leaves until you have a clean, unblemished core, and wash the roots. Replant in fresh soil where ants can’t access it. One way to do this is to place a potted succulent on an elevated stand surrounded by a moat of water.
Diatomaceous earth is a "green" alternative to powders containing pyrethrum. It scratches and penetrates insect exoskeletons, dehydrating them.
See my article: "Ants in Your Succulents? What to Do."
Aphids and Thrips
- Usually not serious
- May cause distorted growth
Juicy, pinhead insects latch onto and suck the juices of tender new leaves, flower stems, and buds. Ants place aphids on plants in order to feed on the bugs' sweet, sticky secretions. Blast pests with a strong spray of water, release ladybugs and other beneficial insects, remove severely infested stems and buds, spray remaining aphids with Isopropyl alcohol, and take measures to prevent ants from accessing the plant.
- Not serious but unsightly
- No known cure
Not much is known about this, but it's likely a fungus. It affects aloes, haworthias and gasterias. It spreads, especially in coastal areas, perhaps due to moist air. Keep leaves dry, locate plants where there's good air circulation, and remove affected leaves, sterilizing tools after each cut.
Leaves of rosette succulents such as graptopetalums, graptoverias, aloes and echeverias change color according to light conditions (the more light, the more rosy the leaves). When transitioning from green to red (or vice-versa), leaves may appear blotchy.
- Unsightly; serious if uncontrolled
Cochineal scale forms dots of white fluff on paddle cacti and will dye your fingertips red if you mash it. Blast the plant with a hose to dislodge the pests, scrub infested pads with a Safer soap solution in summer (use a soft bristled, long-handle brush). Spray with Neem oil in winter, and release beneficial predatory insects (ladybugs) in spring. Poor air circulation, heat and humidity make cochineal scale worse. It's difficult to get rid of if not caught early. If the infestation is severe, pads or entire plants may need to be removed.
Color change (reversion to green)
- Normal if plant is otherwise healthy
Certain succulents---notably crassulas (jades) and aloes---blush red or orange when environmentally stressed, that is, given more sun and less rich soil and water than ideal for optimal growth. Nurseries are pros at producing colorful, healthy succulents because they sell better than plain green ones. When you bring a red, orange, yellow or purple succulent home, give it the same amount of sun, lest it revert to green. Solid green succulents do tend to be more vigorous. To stress a green succulent, increase exposure gradually for a week or so, lest it sunburn.
Crackled, scabby patches
This indicates mycoplasma infection. The bacteria enters the plant's roots and then its leaves from nursery soil that contains horse manure. Once a plant has it in its tissues, there's no getting rid of it except by extreme measures. “It’s not worth trying to treat it,” says echeveria expert Dick Wright. "It's best to simply discard the plants." Notify the plant source, too.
Dead lower leaves
- Normal, if center growth is healthy
New leaves form at the center of a succulent's rosette or from the tip of its stem. Older lower leaves wither and die, and may persist on the stem, thereby shading it from harsh sun and insulating it from cold.
Certain succulents, notably dudleyas, close their rosettes during their summer dormancy to protect their vital cores, so all you see are dead leaves. It’s generally better for the plant to leave them on, because they do have a purpose, but if you find them unsightly, peel them away. Another reason to remove them is they may harbor pests such as mealy bugs.
Large bites taken out of leaves as well as uprooted plants are usually a sign of deer. At first sign of damage, apply a deer repellent. If the situation becomes intolerable, the only recourse may be to surround your garden with 7-foot fencing.
When formerly plump leaves become wrinkled and lose their sheen, it's a sign that they're drying out. During times of drought in their native habitats, succulents live off the moisture in their leaves, so they can survive a lack of water that would kill other plants. So long as the succulent's vital core is healthy and hasn't been compromised by pests that prey on weakened plants, it will recover when watered or the rains return.
Dying after flowering
- Normal for a few kinds of succulents
Plants that are "monocarpic" die after they bloom. Certain succulents, like aeoniums, take several years to flower. Sempervivum rosettes also die after blooming, but like aeoniums, not all in a cluster elongate into bloom at once, so the loss isn't great. Agaves are best-known for being monocarpic, but some (like A. americana) take 15+ years to flower---hence the name "century plant." Less common monocarpic succulents include furcraeas and orostachys. Paddle plants (Kalanchoe luciae) do bloom themselves nearly to death, but unlike true monocarps, plants can be saved if you cut the flower stalk as it forms.
Learn more on this site's About Agaves page.
Also on YouTube:“What You MUST know about Century Plants” (2:50).
Etiolation (elongated stems)
- Not serious
Succulents tend to grow in the direction of greatest sun exposure. Leaves and stems that appear stretched or leaning are "etiolated," a term that means growth that results from inadequate light. Etiolated rosette succulents will flatten to expose more of their surface to the sun.
Provide the plant with more light (gradually, lest it sunburn) and rotate potted succulents and wreaths for even light exposure and to avoid lopsided growth.
Go to my article, How Much Light Do Succulents Need?
See my YouTube video: Sun and Your Succulents (1:41)
Over time, as a succulent's oldest leaves wither, die and fall (or are trimmed) off, branches and stems become denuded.
Snip the healthy tip growth and replant it as cuttings. If you cut above healthy leaves, the stem may branch, creating a fuller plant. If there are no leaves on the truncated stem, new growth along it is unlikely (exceptions are fancy ruffled echeverias).
In the example shown here, a single aeonium has the potential to yield 50 new plants. There's no point in keeping a leggy, leafless succulent, so after harvesting cuttings, discard the plant roots and all.
See my video: How to Redo an Overgrown Succulent Garden (4:49)
- Mild to Fatal
Depending on the type of succulent, how low the temperatures drop (water freezes at 32 degrees F), and how long the frost lasts, plants may show damage only on leaf tips or collapse into mush. When moisture in the cells of a frost-tender plant freezes, it expands and bursts cell walls.
However, some succulents do have a built-in antifreeze, and can survive temperatures well below 32 degrees F---below zero, in fact. Learn more about them on the Cold Hardy Succulents page.
Wait until spring to trim damaged tissue. In winter, check the weather report for your area and cover susceptible plants with frost cloth, floating row covers, or bedsheets.
- Not serious if caught early
If an agave, yucca or cactus keels over, it may have lost its roots to a gopher, a fist-sized mammal that lives underground. Gophers sometimes eat up into a plant’s core if the tissue is soft enough.
If you notice, in your garden, a low mound of fresh soil a foot or so in diameter, or a hole that has been plugged from below with soil, dig down into the tunnel and set gopher traps. Use two per tunnel, one in each direction, to catch the gopher coming or going.
See my video: If I Can Catch Gophers, You Can Too! (2:44)
- Usually not serious
Pock-marked and pitted leaves of succulents often result from impact damage. Not surprisingly, soft-leaved and thin-skinned succulents are especially susceptible.
Prior to a winter storm that might bring hail, move vulnerable potted plants beneath an overhang. Protect in-ground succulents with a lightweight mesh that won’t crease or break leaves and that will let rain through, such as a lean-to constructed of old window screens.
What looks like bits of white lint in leaf axils are mealy bugs. They won't go away on their own, and they can spread rapidly and infest other plants.
Mildew and Fungus
- Persistent in damp climates
Dry-climate plants need low humidity and infrequent water. If leather mildews where you live, your succulents likely will too. Those from arid climates don't thrive in moist, humid, rainy conditions. A tendency to mildew and rot, plus a need for nights colder than days, are generally why it's difficult to grow succulents in the southeastern US, Hawaii, the Philippines and other tropical regions. You can treat with a mildew spray (like those sold for roses), but the problem will likely persist.
Mildew on red apple
- No known cure
First seen during the winter of 2014 in Southern California, entire embankments covered with red apple (Aptenia cordifolia) withered and died, leaving a tangle of dry stems.
Remove them, and when you replant, don't install any kind of ice plant. (The susceptibility of other kinds has yet to be determined.) Go with a nonsucculent instead, such as prostrate acacia shrubs, ornamental grasses, or mat-forming Dymondia margaretae.
- Not serious
The Aloe arborescens in the photo seems unaware that its roots are cramped and lack soil. I suspect that it split its nursery pot, then whoever owned it lazily set it, container and all, atop a soil-filled terra-cotta pot, which being topheavy fell over and broke. This shows how succulents get by with minimal nourishment from their roots. After all, succulents by definition are able to subsist on moisture stored in their leaves. The fatter and juicier a succulent's leaves, the longer it will look OK despite being pot-bound or rootless (although its growth will likely be stunted).
Rabbit and squirrel damage
If you live in an area where predators like coyotes are kept out (like a gated community), bunnies and squirrels may be prolific. Some measures that can help include: Installing an owl box; dusting the plants with crushed red chilis or spraying a repellent. Also, there are solar- and battery-powered electronic devices that emit a high-frequency sound. This one, for about $30 on Amazon, can be set for cats, dogs, skunks, squirrels and raccoons.
Mushy tissue at a succulent's core results when its roots sit in water and rot. If the plant has collapsed, or its leaves have fallen off and the core is mushy, it's not salvageable. If there's still some healthy tissue, remove the plant from its pot or garden bed and trim away damaged stems and leaves until you have a clean, unblemished cutting. Replant in fresh soil that drains well. See my videos, The Squish Test for Succulents (3:36) and Why Succulents Rot and How to Prevent It (2:02).
Grayish-white dots that pepper a succulent's skin are scale insects, which latch onto the plant and consume its tissues. The pests are protected by a hard outer coating, which protects them like armor and makes them difficult to get rid of. It's generally best to bag the plant and put it out with the trash. Thoroughly clean the area around it, and don't put another one in that location for six months.
To prevent scale infestation, give your indoor plants good air circulation and check them often. At the first sign of scale, isolate the plant so it doesn't spread. Scrape off the pest with a plastic knife, wash the leaves with Safer soap, and spray with Neem oil.
- Seldom serious, but unsightly
Snails latch onto leaves and gnaw on them, creating thumb-sized oval holes. Hand-pick the pests and treat the infested area with a biodegradable snail bait that's nontoxic to pets, such as Sluggo.
Stretch marks on cactus
What looks like snail tracks on cactus pads are stretch marks. They appear after winter rains in early spring when the plants are growing rapidly. They don't go away and can't be prevented, but on the plus side, they do indicate that your cacti are thriving.
- Seldom fatal, but unsightly
Succulents that haven't been in full sun and that are exposed to it without time to acclimate will sunburn. This shows up as white or brown patches on the leaves. Unless a secondary condition sets in, such as rot, the plants usually recover.
Sunburn is common on newly planted cuttings that have yet to develop roots, and when bright, hot sun follows days of dim light and cloudy skies. Protect vulnerable plants with a barrier that adds shade or diffuses the sun, such as old window screens, overturned lawn chairs, or whatever else is handy and easily removed.
See my YouTube video: Succulents, Sun and Summer (10:34).
Thin, pale, and spindly leaves often result from undesirable growing conditions: too much sun, too little or too much water, poorly draining or nutrient-deficient soil, too much heat or cold, or pest infestations.
Dig up the plants and re-establish them in amended soil in a more ideal location. If you must leave them where they are, mulch surrounding soil and apply a balanced fertilizer. If too much water is a concern, add a channel to enhance drainage. To prevent water from running off, form a basin around the plant.
More Pest and Disease Resources ...
White fuzzy lumps on paddle cactus are cochineal (coach-en-ee-al) scale, a parasite that pierces the plant’s skin and consumes its juices. It’s used to make carmine dye.
Agave experts, growers, and pest management specialists advise drenching the soil around healthy agaves with a systemic insecticide containing imidacloprid.* Untreated agaves are at high risk of infestation. If treated early enough, an infested agave may survive. The agave snout-nosed weevil is a half-inch-long black beetle with a downward-curving proboscis that enables it to pierce an agave’s…