K-State expert urges gardeners to be on lookout for Septoria leaf spot, early blight
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K-State expert urges gardeners to be on lookout for Septoria leaf spot, early blight

Fungal diseases can affect the year’s tomato harvest, Domenghini says

K-State Research and Extension News Service

Anticipating the upcoming tomato harvest, gardeners need to stay on the lookout for a pair of fungi that threaten to rob the bounty, according to Kansas State University horticulture expert Cynthia Domenghini.

Warm, humid weather and heavy rainfall — conditions witnessed in many parts of Kansas the past week — favor the development of Septoria leaf spot and early blight, she said.

“Septoria leaf spot appears initially as small, water-soaked spots on the lower leaves,” Domenghini said. “The centers of the spots turn light tan or gray, while the margins remain dark. Dark-colored fungal fruiting structures form in the spots, which are typically smaller and more numerous than early blight spots.”

Early blight symptoms appear as irregular, brown lesions or spots on the leaves up to one-half inch in diameter.

“The dark concentric rings in the lesions give the spots a target-like appearance,” Domenghini said. “This is a distinguishing symptom to identify the disease.”

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She added that several lesions can merge together and cause the leaf to yellow, dry up and drop prematurely.

“Leaf drop reduces the plant’s ability to photosynthesize, thus reducing the energy and vigor of the plant,” Domenghini said. “It can also expose fruit to an increased risk of sunscald. Early blight lesions can develop on the stem and fruit, as well.”

Domenghini said that, in Kansas, Septoria leaf spot tends to be more common than early blight. More information on the two diseases is available in a publication available from the K-State Department of Horticulture and Natural Resources titled, Early Blight and Septoria Leaf Spot.

Domenghini and her colleagues in K-State’s Department of Horticulture and Natural Resources produce a weekly Horticulture Newsletter with tips for maintaining home landscapes and gardens.

Interested persons can subscribe to the newsletter, as well as send their garden and yard-related questions to Domenghini at [email protected], or contact your local K-State Research and Extension office.