A physiological disorder associated with insufficient uptake and translocation of calcium to the fruit. For control, ensure adequate moisture and calcium in the soil. It is essential to maintain uniform soil moisture throughout the season. Do not permit plants to wilt during hot days. Do not use urea or ammonium sources of N for sidedressing or fertigation because these forms of nitrogen inhibit calcium uptake. Avoid injuring roots.
Blotchy ripening is most often found in greenhouses and damage to fruit may be significant. It can also be encountered in the field in fresh-market and processing tomato crops. This poorly understood physiological disorder seems to be a consequence of any environmental stress that slows the growth of the plant, particularly sudden stress that occurs at some point early in fruit development. The cause of this physiological disorder and its relationship to "grey wall" is not well understood. Blotchy ripening has been linked to potassium and/boron deficiency and to high nitrogen levels, which promote excessive growth. This syndrome has sometimes been linked to infection by Tomato Mosaic Virus, but this does not seem to be the definitive cause. Weather plays a role in the development of blotchy ripening; the disorder is more prevalent when temperatures are very high. Affected fruit ripen unevenly, with hard, gray to yellow patches. The patches do not turn red, but remain gray or turn yellow. When fruit are cut, the vascular tissues may appear brown and rotted. Growers should provide balanced fertilization and, in greenhouses, avoid excessively high temperatures, if possible. Cultivars vary in susceptibility to greywall. Avoid those varieties which show excessive symptoms. Improper temperatures, moisture levels, cloudiness or nutrition can contribute to this problem. Avoid injury to roots. Do not sidedress with urea or ammonium sources of nitrogen.
See Physiological Disorders in Greenhouse Tomato section.