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Tomato Leaf Diseases Begin and Japanese Beetle Update
By John Fulton

[July 08, 2016]  Tomato Leaf Diseases Begin - Tomato leaf diseases started rearing their ugly head this past week. Some leaves, particularly lower ones, are showing spots, brown leaves, and dropping leaves, or all of the above. Several diseases hit tomatoes, but two of the more common ones are early blight and seporia leaf spot.

Early blight, also know as Alternaria leaf spot, can affect plants at any stage of development. All above ground parts are susceptible. The most characteristic symptom of early blight are spreading spots, ¼ to ½ inch in diameter that form on lower or older leaves. These spots have dark edges and they are usually brown to black in the center. These spots frequently merge forming irregular blotches. Concentric rings often form creating a 'target' or 'bulls-eye' effect. Affected leaves develop yellow areas around the lesions. Spotted leaves soon turn yellow, whither and drop off. The fungus may cause lesions on the fruit around the stem end and shoulder. The lesion is usually dark brown to black, up to an inch in diameter, and with distinct concentric rings.

Septoria leaf spot can also affect plants at any stage of development. Numerous small, water-soaked spots first appear on the lower leaves. These spots soon become circular to angular with dark margins and grayish centers often bearing one or more tiny black bodies called pycnidia which are spore-bearing structures. Individual lesions are seldom more than ⅛ inch in diameter and are usually quite numerous on an infected leaf. Heavily diseased leaves turn yellow, wither and drop off in large numbers, starting at the base of the plant. Defoliation can be severe during prolonged periods of warm, wet weather.

As for what to do, here is the checklist: First, keep ripe fruits picked off the plants. Second, don’t work around tomatoes when they are wet. Next, you can try and improve air circulation, but if your tomatoes are severely affected you won’t want to lose any more leaves. And the final step for this year is to try a fungicide. Mancozeb is probably the recommended one, but it is very hard to find. The other options are Daconil and maneb, which are easier to find but probably won’t give you as good of control. The final step for future years is to practice at least a three year rotation, with good sanitation in the garden.

 Japanese Beetle Update

Japanese beetle numbers have been relatively low this year, but there have been instances of the “hoard” feeding on select plants. Noted feeding has been on fruit trees, crabapples, small fruits such as raspberries, and roses. Many insecticides will control the beetles, but check the label for use on the plants you want to spray and the days to harvest interval.

Hand picking is a possibility on small plants, and an alternative is to disturb beetles over a pail filled with soapy water. When disturbed, the beetles tend to fold wings and legs and drop, If you have the pail in the right place, the beetles should splash.

[By JOHN FULTON, COUNTY EXTENSION DIRECTOR SERVING LOGAN, MENARD, AND SANGAMON COUNTIES]