Spider Mites on dieffenbachia
What's Happening
Spider mites (Tetranychus urticae) infest Dieffenbachia when humidity drops below 40% for extended periods. These arachnid pests thrive in warm, dry conditions and pierce leaf cells to feed on chlorophyll, causing stippled yellowing and fine webbing on undersides. Dieffenbachia's broad leaves provide ideal feeding surfaces, and the plant's calcium oxalate crystals do not deter mites. Heavy infestations cause leaf drop and plant decline.
How to Fix It
- 1
Isolate infested plant immediately to prevent spread to other houseplants
- 2
Shower treatment: Spray entire plant with lukewarm water, focusing on leaf undersides to dislodge mites
- 3
Apply insecticidal soap: Mix 1 tablespoon castile soap with 1 quart distilled water, spray every 5-7 days
- 4
Neem oil treatment: Apply cold-pressed neem oil (1 teaspoon per quart water) to leaf undersides weekly
- 5
Systemic backup: Apply Bonide Systemic Houseplant Insect Control (imidacloprid) to soil per label instructions for severe infestations
How to Prevent It
Maintain 60%+ humidity to create inhospitable conditions for mites. Inspect leaf undersides weekly using 10x magnifying glass—early detection is critical. Isolate new plants for 14 days before introducing to collection.