Marianne's Response
Mildew on tomatoes
I grow heirloom tomatoes in my greenhouse. About 40% of the leaves on all the plants have a powdery, whitish/grayish what looks like mildew on them. Some of the leaves have turned yellow and died. I have cut the leaves up from the bottom about 18 to 20 inches thinking that the plants needed more air circulation. I really need to save these plants as I only eat my homegrown tomatoes!
Posted by CynScotland on July 8, 2016
Marianne's Response
So sorry for your tomatoes! It sounds like they have the dreaded leaf blight and this is a fungus encouraged by dry or stressed plants or by wet foliage and poor air circulation. Open all windows and get the air moving in the greenhouse. Lower the daytime temp with a shade cloth if it is over 90 degrees inside. If half the plant is infected you may not be able to save them. There are some fungicides like Funginex that can help control the spread of this disease. Just follow the instructions on the label. I hope I am wrong and your plants just have mildew on the leaves. If so they will recover if you add air circulation and water properly. You were smart to remove the infected leaves. Good luck, Marianne Binetti
Search the Ask the Gardening Expert library
Looking for a quick resolution to your problem? Marianne has answered thousands of gardening questions. One may be similar to yours. Try searching our library to get the answer you need — fast!