Issues with thyme plants

Asked June 22, 2020, 9:20 AM EDT

I have a 2yr old thyme plant that was doing well, but now the leaves are turning white and the plant has whitefiles. Please help me identify what's going on and what I need to do to bring the plant back to health. I've included pictures of the total plant, a closeup of the leaves showing the discoloration, and a picture of the flies that live in it. Thank you.

Baltimore County Maryland

1 Response

This type of leaf damage could be caused by the flying insects you photographed (leafhoppers) or others that are harder to see, such as thrips and mites. Given what you have seen flying or jumping around, leafhoppers and possibly thrips are most likely. Neither normally needs insecticidal treatment, but with this extensive damage, you can try to control them with one of the following: insecticidal soap, horticultural oil, or spinosad. If this is a plant you are using for harvesting as an herb, rather than an ornamental, make sure the product label mentions it is safe for use on edible plants. Do not spray during temperatures above 85 degrees, and cover as much of the plant (including leaf undersides) as possible. Repeat treatments may be necessary; follow product label directions.

You can also lightly shear the thyme to remove most of this damaged foliage; as it regrows, protecting new foliage with one of the above sprays should help prevent re-infestation. In time, predatory insects should discover these pests and reduce their numbers, though this may happen more effectively if plants are not being sprayed. If any stems are old enough to have become woody, regrowth may be slow or patchy until new stems can fill in.