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Heavy rain during the 4th of July weekend has led to a number of problems in tobacco such as drowning, leaf scald, black shank, wilting and dying. On surviving tobacco, there may be a rapid development of spotting on lower leaves, weather flecking and severe scorching of bottom leaves.
Before the rains came, there were already foliar symptoms of deficiencies of nutrients like nitrogen, potassium and phosphorus, which were directly related to poor root development resulting from generally wet soil conditions that had prevailed during the early season.
The current tobacco leaf spotting is believed to be the result of an interaction between stressed tobacco and the environment. One concern is what to do in fields where this spotting is occurring. There is difficulty in deciding what to do because the exact cause of the problem is not clearly understood. However, growers should consider the following points.
An application of Quadris is recommended for growers who have not applied it already. The standard 8 ounces per acre should be sufficient for protection, and growers who are seeing disease already should consider 10 to 12 ounces per acre.
The nutritional problems that we’re seeing right now are not generally associated with deficiencies in the soil, but instead are a result of the inability of roots to reach nutrients that are already there.
Side-dressing would be of potential value if nutrients can be placed into the root zone without creating additional damage. For tobacco that is waist-high or bigger, do not apply more than 25 pounds of actual Nitrogen (N) per acre. For tobacco that is smaller than waist-high, use no more than 50 pounds of actual N. Ammonium nitrate would be the ideal N source, but liquid N (UAN) would be an acceptable alternative.
For potash, 100 pounds per acre of sulfate of potash (0-0-50) should be sufficient.