Brown spots destroying mint, mums, daisies etc.

Asked July 10, 2020, 10:25 AM EDT

These brown spots started appearing on everything around the yard. It destroyed most everything in my container vegetables. Then I noticed it was on mums, mint plants, daisies in the regular garden. Different greenhouses tell me to use something different. Nothing seems to work. No rain For weeks, so it’s not being washed off.

Kent County Michigan

1 Response

This is damage caused by an insect known as four-lined plant bug. This insect won't kill plants but when we have high populations, such as this year, the plants look pretty ragged. The plant should grow out of this damage as shown in the mum photos. In future years, look for the immature plant bugs and adults in May and June. If they are present in high populations, a contact insecticide may be used to reduce populations and resulting damage.

Here is an article on four-lined plant bugs with images of both the adult and immature (nymph) life stages written by my colleague at Ohio State. Contact insecticide options are also listed. Note these are the actual chemical names listed under "active ingredients" on the produce label. https://bygl.osu.edu/node/1054

I hope this information is helpful.