Knowledgebase

How to treat downy mildew on Thai basil? #838445

Asked June 30, 2023, 3:12 PM EDT

Hello, starting last year, I've been getting downy mildew on my Thai basil plants--those I buy and those I grow from seed. I don't have this problem with Italian basil because I only buy resistant variety seeds. There seems to be a widespread belief that the Thai basils are resistant, but they certainly aren't! I'm actually growing Thai basil inside my house this year (in AC) because Maryland is so humid. But I'm still seeing affected leaves. Is there anything home growers can use to treat this fungus? I just grow these as part of my personal kitchen garden and I've been really careful not to ever take these plants outside. Thanks for any advice.

Carroll County Maryland

Expert Response

Hi, 

Downy mildew is definitely a nuisance to deal with for basil growers. We have undergone trial plantings to try to determine the most resistant varieties that seem to have the most success. Usually Thai Basil doesn't have as many problems with downy mildew as the sweet basil varieties do. 

Unfortunately there are not any fungicides recommended for downy mildew so just harvest what you cant and clip and bag and discard severely infected plants. You can continue to plant new seeds or transplants to get enough to harvest. Sunny location with good air flow and not crowded with other herbs is best if you have the space for it. You can also try to thin out stalks of the plant to provide more air circulation. 

Emily 

Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied July 03, 2023, 1:30 PM EDT

Loading ...