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Aloe mite (c) Debra Lee Baldwin
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How to Manage Aloe Mite

They seem everywhere this spring: mite-damaged aloes ranging from dwarf cultivars to tree ‘Hercules’. The microscopic pests (Eriophyes aloines) are not insects but spider relatives. They cause deformed flowers, a bubbly fringe on leaf edges, and orange-and-green growths where leaves meet stems.

Aloe mite (c) Debra Lee Baldwin
Aloe mite on Aloe arborescens ‘Variegata’

Google “aloe mite treatment,” “aloe mite prevention,” “aloe gall” or “aloe cancer” and you’ll discover that distinguished experts, landscape designers, succulent societies and growers, and even federal agencies are aware of the problem. Yet they don’t agree on what to do about it. Environmentally-unfriendly chemicals supposedly help to some extent, but are expensive, come with cautions, and aren’t allowed in certain states (like California). 

Mites, protected within galls, are impervious to topical pesticides. To protect rare and valuable specimens, aloe growers and collectors may apply a preventive systemic—a miticide that’s taken up into the tissues of the plant via the roots—but it has to be applied before there’s evidence that it’s needed. 

Aloe mite (c) Debra Lee Baldwin
Aloe mite on dwarf aloe

Here’s what to do: At first sign, excise affected tissues and bag them for the trash (do not put them in green waste). If an infestation is severe, dispose of the entire plant. After all, it’s a breeding ground. Even if you don’t mind the galls, do get rid of them before the pests inside them find your neighbors’ aloes…or mine. [Update: See expert Duke Benadom’s comment below.]

Mites inject a chemical that causes cancerous growth. They produce as many as eight generations a year, and each female lays 80 eggs a month. Mites travel via water, wind, garden tools, and people who find bizarre formations fascinating. 

It’s not the end of the world. These photos, taken in my own garden, show two different aloes six weeks after gall-removal surgery. I simply used a sharp knife to slice the plants well below any signs of infestation.

Aloe nobilis (c) Debra Lee Baldwin
Aloe nobilis, new growth
Aloe rupestris (c) Debra Lee Baldwin
Aloe rupestris, new growth after gall removal

Other Pests and Problems

Lush green growth after winter rains means that insects of every kind—indeed, the entire food chain—are proliferating. Find out “What’s Wrong with My Succulent?” and what to do about it on my website, my YouTube channel, pages 76-77 of Succulents Simplified and 137-142 of Designing with Succulents

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Ants in Your Succulents? What to Do

Late summer into fall, Argentine ants like to nest in the root balls of potted plants. Haworthias, aloes (especially dwarf varieties), gasterias and gasteraloes are highly vulnerable. Ants overwinter in the soil and consume the plant’s juicy core. Leaves eventually fall off and the plant dies.

Argentine ants infest a haworthia

The first line of defense is to create a barrier around your pots using ant powder or diatomaceous earth. The latter, available at garden centers and online, is the best “green” solution. (Go to my Useful Tools page for more about it.)

Rinse ants out of the rootballIf an infestation is well underway—ants swarm when you water the pot or tap it on a hard surface—unpot the plant and wash the roots until pests are gone (you may want to wear gloves). Before replanting in fresh soil, place a square of fine-mesh screen in the pot to keep ants from re-entering the drain hole. I know it’s overkill to buy a roll of screen for a single pot, but really, you should be using it in ALL your pots. It’s surprising how quickly you’ll go through it, especially if you repot your plants often. A role isn’t expensive and you can always share it with friends.

Pot in a moat of waterMove the plant to a different location and/or surround it with a moat (ants can’t swim). Add water to a bowl or other shallow container and, to keep the drain hole above water, set the pot atop rocks or gravel. Be vigilant until the weather cools in October.

Mealy bugs on aloe

Ants “farm” other pests for their sweet secretions. The best preventative is good air circulation. Aphids attack new growth, and mealy bugs (shown below) nestle under leaves and in leaf axils. Spray with isopropyl alcohol (70%). Isolate plants you’ve treated, and trash any that are badly infested. Indoor plants are especially susceptible, so run a fan in the room in which you overwinter your succulents. If you find pests on one plant, be sure to check its neighbors.

Also see the “Pest and Damage Control” section of Designing with Succulents, 2nd ed (pp 137-142); the “Pests and Diseases” page of my website, and my YouTube video, “Oh, No! Something’s Wrong with My Succulent!”