Yellowish spots with grey outlines
(White Rock, BC)
Q. My tomato plants have yellowish spots with grey outlines, mostly on the lower leaves. Not sure what it is, but there are no fruits on the plants yet, just flowers. It is a cherry tomato plant. Last year my plants got late blight, but I'm not using the same space as these newer plants are in a pot about 20 feet from the garden I used last year.
If anyone can help that would be great.
A. Yellowed leaves can indicate several conditions.
- Septoria leaf spot. Round, yellow or water-soaked spots appear on the undersides of leaves. They quickly emerge on leaf tops and turn to black or brown with tiny black dots in the center.
Heavily infected leaves turn completely yellow, then brown, and fall.Spotting works its way up the plant and can infect stems.
- Early blight. Dark, concentric spots (brown to black), ¼ - ½” in diameter, form on lower leaves and stems. Lower leaves turn yellow and drop.
- Gray leaf spot. Spots develop a gray center surrounded by a yellow halo. Leaves turn yellow, then brown, then drop.
In all three cases, the treatment is similar. Treat organically with a biofungicide like Serenade
to lessen symptoms. Follow label instructions. Or apply a fungicide such as chlorothalonil (sold as Fungonil)
, Mancozeb fungicide
, or maneb (all available under trade names) at the first sign of spot, when fruit sets (as a preventative measure) or when conditions indicate a strong potential for it to develop. Follow label directions. Re-apply every 7-10 days or after rain.
Good luck and happy gardening!Your friends at Tomato Dirt