Spider mites
Almost invisible without a hand lens. Yellow-green to red-orange specks running along the underside of the big leaves, especially near the central vein. Indoor heated air dries banana's huge leaf surface and triggers a population boom in weeks.
Pale tiny pale dots spreads across the broad leaf face, then whole leaves bronze and crisp at the edges. Fine webbing strung along leaf-pseudostem junctions on heavy infestations. Banana's enormous leaf area means damage looks dramatic fast, even when colonies are still small.
Shower the leaves weekly for 3 weeks
Move the banana to the shower or carry it outside with a hose. Spray cool water on the underside of every leaf for 30 seconds per leaf. Mites can't reattach quickly when knocked off. Banana loves the rinse and the leaves dry fast in good airflow. Repeat weekly for 3 weeks.
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 leaf-pseudostem junction where mites cluster.
Repeat every 5 days for 3 rounds. That covers the full egg-to-adult cycle.
Raise humidity above 50%
Run a humidifier near the plant for 50 to 60% relative humidity. Banana is a tropical and wants the moisture anyway. Hot dry indoor heating is the climate mites need to breed fast on those big leaf surfaces.
