Spider mites
Almost invisible without a hand lens. Yellow-green to red-orange specks on the underside of leaves, especially along the silvery veins and the central rib. Dry indoor heated air is the climate they need to explode on Alocasia wentii.
Pale tiny pale dots that quickly bronzes the big arrowhead leaves. Fine webbing along the leaf-petiole joint and across the silvery vein lines. Alocasia drops stressed leaves fast, so an unchecked infestation can strip the plant in two to three weeks. The rhizome usually survives once mites are cleared.
Gentle shower on every leaf, weekly for 3 weeks
Move the plant to the shower or sink and rinse the underside of every leaf with cool water for about 30 seconds per leaf.
Use gentle pressure. Alocasia leaves bruise under aggressive scrubbing, so let the water do the work.
Tip the pot afterward to drain any water sitting in the central crown, since standing water there causes rot.
Repeat weekly for 3 weeks to cover the full egg-to-adult cycle.
Neem oil at lights-out, every 5 days for 3 rounds
Mix 2 tablespoons cold-pressed neem oil and 1 teaspoon dish soap per gallon of water.
Spray top and bottom of every leaf at lights-out, paying special attention to the silvery veins and the leaf-petiole joint where mites cluster.
Repeat every 5 days for 3 rounds. That covers the full life cycle.
Raise humidity above 60%
Run a humidifier near the plant for 60 to 70% relative humidity. Alocasia wentii is a tropical understory plant and wants the moisture anyway. Hot dry indoor heating is what lets mites breed fast on these big leaves.
Pyrethrin sprays from the hardware store kill them.
Spider mites are arachnids, not insects, so most household bug sprays barely affect them. Use neem oil or a true miticide instead. Alocasia leaves also burn under high-pressure aerosol sprays, which makes the wrong product double trouble.
