NDSU Extension - Griggs County


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July 27

The Extension Connection

By Megan Vig

                It’s BLT season!  The crunchy, savory sandwich of summer.  What makes the BLT so refreshing to you?  I personally love the T of BLTs.  Tomatoes are beginning to turn red and making their way to kitchen counters while tomato diseases are starting to show up. This week I share information on healthy tomato vines from the NDSU Extension Yard & Garden Report.

                The most common diseases are Septoria leaf spot (Septoria) and early blight (Alternaria).  Septoria appears as tiny, 1/8-inch-diameter brown spots with dark borders whereas as early blight lesions may become ½ inch or larger, with concentric rings and surrounded by yellow blotches.  The following are tips on how to protect your tomato vines.

                Water the roots, not the leaves.  Diseases need water on the leaves for infection.  Avoid overhead watering.  A soaker hose is ideal.  Irrigate in the morning so any water that gets on the foliage can dry before nightfall.  Avoid splashing the soil and its infected debris onto the leaves.  Avoid working in the garden (and spreading the disease) when the vines are wet.

                Stake and prune vines.  Staking and pruning will increase air flow and help vines dry out.  You may remove up to one-third of leaves at the base to increase air flow and prevent the infection of leaves near the soil. 

                Remove severely infected leaves.  Focus on the older and lower leaves, where the diseases will start.

                Apply mulch around the vines.  Straw, black plastic or landscape fabric can reduce soil splashing.  Lawn clippings can be used if they have not been treated with an herbicide. 

                Apply protective fungicides.  Chlorothalonil (Daconil, Bravo), mancozeb (Dithane), maneb and copper-based products are often used.  Spray a few days before rains are expected so the chemical is absorbed and can act as a shield.  Spray every 7-14 days if needed.

                Keep in mind it is unreasonable to expect disease-free vines, but we can slow the spread of diseases and maximize yields until frost.


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