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.
Not serious but unsightly.
Damage is permanent.
Agave edema results from inconsistent watering. Blisters form on leaves and the skin sloughs away. There’s no reversing the damage. Check to make sure large agaves are watered minimally and infrequently. The edema on this particular Agave franzosinii resulted from a pipe that broke beneath the plant.
Agave snout weevil
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. At the first sign of infestation, remove the plant lest the pest move on to healthy agaves. Drench the ground below and around it and other agaves in your garden with systemic insecticide. Plant new agaves bare root only, in pots atop the ground. For detailed information on how to control this serious pest, watch my video, “Agave Snout Weevil Prevention and Treatment” and read my online article with the same title.
Serious because it spreads
No known cure.
A microscopic mite causes bubbly, tumorlike growth on aloes, especially along leaf margins and flower spikes, and where leaves meet the stem. Once the mite is in a plant’s tissues, it’ll continue to cause cancerous growth. Discard the plant 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. Keep in mind that aloe mite is still going to show up on that particular plant. Even if it looks fine, don’t give friends cuttings from an infested aloe.
Plants may 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.
May cause distorted growth
These 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 the 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 will spread, 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 your 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.
Not serious but unsightly
Cochineal scale forms dots of white fluff on paddle cacti and will dye your fingertips red if you mash it. Blast the plant with hose water to dislodge the pests, spray the pads with Neem oil in winter, and release beneficial predatory insects (ladybugs) in spring. Poor air circulation and humidity may make cochineal scale worse. It can be difficult to get rid of if not caught early; if the infestation is severe, plants may need to be removed.
Color change (reversion to green)
Normal if plant is otherwise healthy
Certain succulents—notably crassulas (jades) and aloes—will 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, then don’t give it the same amount of sun, it may revert to green. On the plus side, solid green succulents do tend to be more vigorous; they’ll grow larger more rapidly than their colorful cousins. If you decide to stress a solid green succulent, increase the amount of exposure gradually for a week or so, lest it sunburn.
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 is usually a sign of deer. At first sign of damage, apply a deer repellent that contains garlic. If the situation becomes intolerable, your 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.
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.
As a succulent’s oldest leaves wither, die and fall (or are trimmed) off, branches and stems become bare over time. 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 is unlikely (although there are exceptions, such as fancy ruffled echeverias). There’s no point in keeping a leggy, leafless succulent, so discard it, roots and all. In the example shown here, a single aeonium has the potential to yield 50 new plants.
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. But these are the exception, and tend mainly to be in the genera Sedum or Sempervivum. Crassulas, aeoniums, euphorbias, and kalanchoes are among the most frost tender. Most aloes, echeverias, cacti and agaves can go a few degrees below freezing, although they may show tip damage. 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 small mammal that lives underground. Gophers may 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.
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 will spread rapidly and infest other plants. Isolate affected succulents and spray the pests with Isopropyl alcohol.
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 ice plants has yet to be determined.) Go with a nonsucculent instead, such as prostrate acacia shrubs or mat-forming Dymondia margaretae.
Chewed tips of aloes, haworthias and other rosette succulents are usually caused by rabbits. Move potted plants where bunnies can’t get them, and surround in-ground succulents with fencing and wire mesh.
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.
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, scrape off the pest and wash the leaves.
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 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 will recover. Sunburn is common on newly planted cuttings that have yet to develop roots, and whenever bright, hot sun follows days of dim light and cloudy skies.
Thin, pale, and spindly leaves often result from poor growing conditions: too much sun, too little water, nutrient-deficient soil, and too much heat or cold. Dig up the plants and re-establish them in amended soil in a more ideal location. If you must leave them where they are, apply a balanced fertilizer, form a basin around them to hold water, and increase the amount they receive.