Hi everyone,

I am new to this site and I would like to ask you guys about a problem I have been having with my herbs for about a year now. There are black dots under the leaves (sometimes on top of the leaves as well) of my chocolate mint, mint, thyme and lemon thyme plants. I had it in my oregano first and the plants started to produce less and less leaves even though the root system seemed healthy and I had to cut it down to the ground. It never grew back. Any suggestions as to what this could be and how to treat it?

Hmmm, black fungus. Not healthy, in your soil as well. If the leaves of mint were less soft you might could wash it off with soapy water like we do citrus leaves. Have you used a neem oil spray? Powdered cinnamon on the plant and soil to help fight the fungus? Luck to you

I'm pretty sure that's a leaf sucking critter that's doing the damage. It's hard to tell from the photo, do the little black dots rub off, if they do, is what rubs off juicy or dry?
Aphids and spider mites sometimes infest oregano plants. You can control mild infestations with a strong spray of water from a hose every other day until the insects are gone. Once knocked off the plant, these insects are unable to return. For stubborn infestations, use insecticidal soap or neem oil spray.

We both should have asked about your humidity and soil types, chuckl. San Diego is dry air, black fungus and mold arent really issues. Where I live humidity averages 98% to 60% most of the time. Even the dew rises 3' hi on the plants at 63*F. Black molds, fungus is sooty colored. I know of no tiny black bugs that congregate like that. Leaf sucking bugs cause the leaf to yellow and rot at the bite. I am still learning tho, so it is possible I am wrong. Plants planted in a potting medium hold too much moisture for a 'weed' type plant such as oregano and mints. Many mints grow only in cooler weather by the way. They dont take to being watered if you have any amount of rain- or dont water more than every 2 weeks. Oregano needs heat, mint needs partial shade and cooler temps. Never reuse potting soils and sterilize if possible. Luck.