Rain and heat usually are good for summer tomatoes. But too much of a good thing is causing trouble for South Carolina gardeners this year.

Early heat that stressed plants followed by heavy rains have contributed to what Clemson Extension Service agent Powell Smith calls an above-average outbreak of early blight, a fungal infection that harms tomato plants, mostly in home gardens.

North Carolina hasn’t seen as much problem with the disease, according to farmers and extension agents.

Two kinds of blight can affect tomatoes. Early blight is a fungus that starts in the leaves lower in the plant and moves upward, infecting leaves with distinctive target-shaped spots of dark lesions surrounded by a yellow halo. You end up with a sick-looking plant with crispy, burned-looking leaves on the bottom and greener leaves toward the top.

Late blight, which can come with cooler weather in the fall, affects both tomatoes and potatoes and can cause much more damage to horticulture. It’s the same fungus that caused the Irish potato famine in the 19th century.

A couple of cases of late blight have been spotted this year in North Carolina, according to the N.C. Department of Agriculture. One was in Sampson County and the other was at the Mills River Research Station south of Asheville. While that’s earlier in the season than usual, both outbreaks are being treated.

While early blight dogs home gardeners, it doesn’t really harm commercial crops or tomato prices, Smith said. Commercial growers expect early blight and compensate with resistant varieties and sprays.

Scott Ewers, horticulture agent for Mecklenburg Cooperative Extension, says gardeners usually don’t notice the infection until it has spread through the plant. “And a lot of times, it’s too late.”

Ewers hasn’t had many calls about it this year, even though conditions have been right for an outbreak in the Charlotte area.

If you have an infected plant, you can pull off the diseased leaves to slow the spread, says Ewers. Spraying fungicide is costly, particularly this late in the tomato season. “You may be able to buy tomatoes for that price.”

Powell Smith in South Carolina suggests not composting your tomato plants at the end of the season. If blight is present, it can be reintroduced into your garden next year.

Dane Fisher of Fisher Farms in Richfield, who sells tomatoes at the Matthews Community Farmers Market, says he hasn’t had trouble with blight. He’s had more trouble with his tomatoes all ripening at once because of extremely high heat a few weeks ago.

“I’ve got a barnful of tomatoes. I won’t be able to get rid of them all,” he said Tuesday. “Three weeks from now, we won’t have any.”