Many common summer tomato troubles are easier to prevent than to cure.
Blossom-end rot (BER) is a serious problem of ripening tomatoes. As the fruit ripens, the blossom-end turns dry, brown and leathery. It is caused by a calcium deficiency in the fruit. In addition to low soil calcium, the following conditions may increase BER: high nitrogen rates, using ammoniacal nitrogen, high concentrations of soluble potassium and magnesium in the soil, inadequate soil moisture, excess soil moisture and heavy pruning. Foliar applications of calcium materials have not proven to reduce BER, since very little calcium is taken up by the fruit and that taken up by the leaves cannot be translocated to the fruit. It’s best to prevent BER with proper fertilization and good water management.
Catfacing is a condition in which the fruit is malformed or irregularly shaped, often with brown scars at the blossom-end and sometimes running up the side of the fruit. The blossom-end of the fruit may be puckered with deep crevices. Catfacing does not affect the edibility of the fruit. Just cut off the scars and eat the rest of the tomato. It usually only affects the earliest fruit set. The deformity is caused by something that occurs during the formation of the flower that results in the fruit not developing normally. A common cause for this condition is cool temperatures at time of pollination and during early growth of the fruit. Heavy pruning in indeterminate varieties has been shown to increase catfacing. Drifts of common lawn herbicides such as those containing 2,4-D can cause fruit to catface. Heavy thrips feeding on young fruit can cause a type of catfacing. There is not much that can be done for control. Varieties should be selected that historically have had little problem with catfacing. Possibly plant a little later to avoid the cool early spring temperatures during pollination. And, try to prevent spray drift from lawn herbicides.
Fruit cracking can be caused by periods of very fast growth during times of high temperature and moisture supply or by rains after a dry period. Not all cracking can be avoided but you can lessen its severity by selecting tolerant varieties and by reducing fluctuations in soil moisture.
Sunscald appears as a white-blistered area on the top of the tomato. The area can turn leathery and be invaded by rots. Over pruning can increase sunscald problems especially with fruit in the upper part of the plant. Also good spray programs to ensure good foliage cover can reduce the problem.
Visit http://edis.ifas.ufl.edu/hs200 for more information on tomato troubles.
Larry Williams, UF/IFAS Extension Agent, Okaloosa County, July 2, 2014