RPD No. 906 - Blossom-End Rot of Tomato
[ Symptoms ] [ Table 1 ] [ Control ]
Blossom-end rot is a noninfectious disease
or disorder of tomato (and pepper) fruits caused by low levels of calcium
in fruit. The disease occurs to some extent wherever tomatoes are grown.
Losses of fruit vary from a tracer up to 70 percent, depending on the
year, variety, method of culture, weather, and location. Few to many fruit
on each plant may be affected. Blossom-end rot occurs frequently where
large fluctuations in soil moisture are allowed to occur. It is usually
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The first external symptom is a small, somewhat watersoaked spot at or near the blossom end of the fruit. It occurs most often on fruit one-third to two-thirds mature. The area enlarges and becomes dry, sunken, flattened, brown to black, and papery or leathery (see illustration). The veins may show through the lesions as black lines. When the disease is severe, 560 percent or more of the tomato may be affected. There is no soft rotting of the fruit unless the affected areas are invaded by secondary decay fungi and bacteria. Affected fruits usually ripen earlier than healthy ones.
Conditions favoring blossom-end rot also favor noninfectious leaf roll. Blossom-end rot is most common when there are: 1) prolonged dry periods; 2) frequent or heavy rains followed by an extended period of dry weather; 3) soil conditions unfavorable for uptake of calcium; 4) excessive soil salinity; and, 4) root damage from infectious diseases. Other factors favoring blossom-end rot include early planting in cold soils, poor fruit setting, and high temperatures. Any condition that reduces the ability of the roots to absorb water and, hence, soluble calcium salts predisposes the plant to blossom-end rot. Some factors that could affect the roots are root-rotting fungi, nematodes, underwatering, overfertilizing, root pruning due to cultivation or insect feeding, and lack of aeration due to soil compaction or overwatering. Losses from blossom-end rot increase when the soil contains an excess of total soluble salts in relation to soluble calcium salts. An excess of soluble ammonium, potassium, magnesium, or sodium salts reduces calcium uptake by the plant. Blossom end rot is rarely a problem in soils where calcium is available in proper balance with other available nutrients. Sometimes rapid luxuriant plant growth accentuates development of the disorder, because the new growth draws heavily on the available supply of calcium in the soil. Calcium is not translocated within the plant from older to younger tissues. Therefore, injury may appear on the blossom end of the young fruit, which is especially sensitive to a lack of calcium. Some tomato varieties are much more susceptible to blossom-end rot than others (see Table 1). Generally, elongated pear and plum tomatoes used for processing and canning are prone to this disorder.
Figure 1. Blossom-end rot of tomato.
Table 1: Incidence of some tomato varieties to blossom-end rot grown at the Dixon Springs Agricultural Center under irrigation.
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Information concerning insecticides, weed control, varieties, and other recommendations can be found in the Illinois Homeowners' Guide to Pest Management, available at your nearest Extension office.[an error occurred while processing this directive]