Tomato Diseases are Upon Us and Japanese Beetle Update
By John Fulton

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[July 31, 2014]  Tomato Diseases are Upon Us - This is another one of those columns which can be used most years, and this year is no exception. Tomato disease symptoms are worse this year than most, with fruit being affected in many cases. Most of the samples I have seen have 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 known 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.

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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 option is Daconil, which is easy 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. This rotation would also include peppers and potatoes as hosts of the diseases as well. 

Japanese Beetle Update

Most areas have experienced relatively few Japanese beetles for the second year in a row. Many credit the extreme cold, but probably just as important were the really poor egg laying and grub survival conditions of the past two summers. Laying eggs into dormant grass (due to the heat and dryness of the past two summers after July) doesn’t bode well for survival. Darn….. Also, the natural diseases and predators of the grub have caught up. The exception is once again the advancing wave of the beetles where there are many more present. Most of our local areas will have no need to treat for the grub stage of the Japanese beetle this year due to low numbers of grubs and good growing condition for lawns.



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