Thrips (Thysanoptera) are small puncturing insects that make tiny holes in the leaves of houseplants that leave a speckled white and yellow appearance to the leaves and some leaf curl. They are very tiny and can go  unnoticed. Aphids cause similar leaf mottling but thrips leave black specks behind as well, which are their byproduct.

There are blue cards covered with an oily film that can be used in the planting area to identify when thrips are present. You can minimize the likelihood of an infestation by keeping plants just on the moist side (thrips like dry conditions) and increasing humidity in the growing area. Make these adjustments minor so as not to invite other varieties of problems!

Inspect the plants regularly. New infestations are easier to control. Good quality insecticidal soap can be used to treat a small occurrence. Use a commercial product rather than a home remedy because dish soaps can have a variety of plant-harmful ingredients. Test the product first on just a portion of the plant and keep the plant out of direct sun while it is wet. Be thorough and repeat every ten days until there is no evidence of insect activity on the indicator card.

Superior grade horticultural oil can also be used to smother thrips. Test the product first on just a portion of the plant and keep the plant out of direct sun while it is wet. Like insecticidal soap, the treatment should be repeated at regular intervals until no insect activity is detected. Consistency is important.

Thrips will affect a variety of houseplants, so keep plants isolated while you treat them.

Courtesy of NYBG Plant Information Service