How to Kill Spider Mites on House Plants

Spider mites are tiny plant pests that are closely related to ticks and spiders. These common pests are difficult to see with the naked eye (they only measure about 1/50th of an inch when full-grown) and can be very difficult to remove from house plants, as there are no effective biological controls and few chemical ones. The first sign of spider mite infestation is the appearance of yellowish discoloration on the underside of the plant's leaves.

Things You'll Need

• Pruning scissors
• 1 quart water
• 1/2 tsp. mild detergent
• Soft cloth
• Insecticide with bifenthrin (optional)
• Horticultural oils (optional)

Instructions

1. Test for the presence of spider mites by placing a white sheet of paper under a discolored leaf and tap the leaf gently. Check the sheet of paper for any tiny, moving insects.

2. Trim the most heavily infested leaves from the plant and dispose of them.

3. Mix 1/2 teaspoon of a mild detergent with a quart of lukewarm water. Dip a soft cloth in the solution and wipe down any smooth leaves.

4. Use a chemical control if the problem persists. Carefully read the label of a bifenthrin insecticide or horticultural oil and apply it to the leaves of your house plants. Repeat as necessary.

5. Dispose of any plants that are severely infected to avoid the spread of spider mites to other plants.

Tips & Warnings

• It is important to treat all of your house plants at the same time, even if you don't suspect a spider mite infestation on all of them.

• Read all insecticide labels carefully.

• When using chemical controls, always apply in an open, well-ventilated area.

References

• Colorado State University Extension: Spider Mites
• University of Minnesota Extension: Houseplant Insect Control