According to Texas A&M AgriLife Extension “If you have ever had tomato leaves turn yellow, then brown, then die from the bottom of the plant you are not alone. This is something we commonly see in our area. This is the result of a fungus infecting the foliage causing a disease known as early blight. Early blight is an annual problem for most gardeners. It normally develops into a problem when plants have a heavy fruit set and the area has received rainfall. Spores from the fungus are spread to the lower foliage by wind and splashing rain. Leaves must be wet for infection to occur.
At 50 degrees F. the leaves must be wet for twelve hours for infection, but at temperatures above 59 degrees F., the length of time for infection is only three hours. Leaf spot development is most severe during periods of cloudy days and high humidity. To control the fungus, foliage applications of a fungicide must be made every seven days until moist conditions (dew included!) no longer exist. Applications should begin when the first fruit is slightly larger than a quarter. There are several fungicides which can be used on tomatoes for early blight.
What is causing my tomatoes to crack?, is a question often asked in the county extension office. Cracking is a physiological disorder caused by soil moisture fluctuations. When the tomato reaches the mature green stage and the water supply to the plant is reduced or cut off, the tomato will begin to ripen. At this time a cellophane-like wrapper around the outer surface of the tomato becomes thicker and more rigid to protect the tomato during and after harvest. If the water supply is restored after ripening begins, the plant will resume translocation of nutrients and moisture into the fruit. This will cause the fruit to enlarge; which in turn splits the wrapper around the fruit and results in cracking. The single best control for cracking is a constant and regular water supply. Apply a layer of organic mulch to the base of the plant. This serves as a buffer and prevents soil moisture fluctuation. Water plants thoroughly every week. This is especially important when the fruits are maturing. Some varieties are resistant to cracking, but their skin is tougher.
Another common problem among tomato growers that we hear a lot about in our area is Blossom End Rot, caused by improper (fluctuating from too dry to too moist) moisture. Calcium deficiency is also associated with the physiological disorder. There are a few things that can be done to correct the problem. First, maintain uniform soil moisture as the fruit nears maturity.Also, remove affected fruit because it will be unfit for consumption. A solution for next year’s crop would be to lime the soil with Ag. Lime (Calcium carbonate) to add calcium to the soil. Also, using calcium nitrate fertilizer for part of your fertilizer regiment may also help”. For more information on this or any other agricultural topic please contact the Hopkins County Extension Office at 903-885-3443 or email me at m-villarino.tamu.edu.