Alocasia pests: spider mites and thrips, how to spot and treat them
August 22, 2026
Alocasias have two enemies that always come back: spider mites and thrips. Both are tiny, both start on the underside of the leaf and both are noticed late if you don't know what to look for. Here's how we recognise them, how we treat them at home and how we stop them coming in with a new plant.
Spider mites: the dust and the webbing
Mites less than half a millimetre, reddish or yellowish in colour. Signs: little yellow or silvery dots scattered over the leaf, as if it were “faded” by pinpricks, and in advanced stages a very fine webbing on the underside and in the leaf axils. They appear when the air is dry and warm: heating in winter and summer without a humidifier are their moment.
- Treatment: shower the whole plant with lukewarm water, especially the underside. Then, potassium soap (at the manufacturer's dose, normally 10-20 ml per litre) sprayed every 4-5 days for 3 weeks; the full cycle from egg to adult lasts between one and two weeks, and it has to be broken several times.
- What helps most: raise the humidity to 60% or more. With high humidity spider mites barely thrive.
- If it doesn't ease off: neem oil in alternate sprays, or predatory mites (Phytoseiulus persimilis) if you have many plants.
Thrips: the silvery streaks and black dots
Elongated insects 1-2 mm long that run across the leaf and jump. Signs: elongated silvery marks, sometimes with irregular edges, and little black dots (their droppings) on the underside. New leaves come out deformed or with “scars” because they bite them while they're still rolled up. On variegated ones, the white or yellow part is the first to show the damage.
- Treatment: blue sticky traps for the adults and potassium soap + neem every 4-5 days on the leaves. The larvae pupate in the substrate, so it's worth watering once with a biological insecticide (Beauveria bassiana or nematodes Steinernema feltiae).
- Consistency: at least 4 weeks, even if you no longer see any. The eggs are inside the leaf tissue.
- Quarantine: keep the affected plant apart from the rest until 2 weeks pass with no new damage.
Prevention: what we do with every new plant
Every plant that comes into the house spends 10 days apart, with an inspection of the underside with a torch or magnifying glass every two days. Ours leave clean, but the best habit is not to trust any, not even ours. A humidifier and wiping the leaves with a damp cloth every couple of weeks removes eggs and lets the leaf breathe. And if you buy a corm instead of a plant, the risk of bringing in a pest is almost zero: there are no leaves to hide in.
How to receive a new plant and what to do in the first week is explained in acclimatising an Alocasia that just arrived.
Texto redactado con ayuda de inteligencia artificial y publicado por el equipo de Marina’s Jungle Gems.
