Blossom end rot scourge of tomato gardens
By Hugh G. EARNHART
OSU Ext. master gardener volunteer
From seed catalogs and nurseries an individual can purchase 111 individual heirloom and hybrid tomato plants. Then the race is on to be the first tomato connoisseur in the neighborhood or garden club to have a ripe tomato. The vegetable gods are smiling on you until suddenly the scourge of the tomato kingdom strikes – blossom end rot.
It looks like fungus diseases, but it is not. Blossom end rot is a grim nonparasitic, noninfectious tomato plant disorder caused by low levels of calcium within the plant. It is not associated with soil contact or with damage to the plant structure. The condition usually follows extremes in soil moisture either too dry or too wet. The fruit rot on the bottom of the tomato fruit is a result of the low level amount of calcium available to the growing fruit.
The first visible symptom of this disorder is a darkened spot that encircles the blossom end of the tomato (bottom) about the time the fruit is starting to ripen. The rot usually causes the tomato to ripen early and makes it inedible.
The calcium deficiency causing end rot is most often a result of climate or cultural problems. The severity of this condition is compounded when calcium, nitrogen, and soil moisture levels are out of balance. The physiology of the tomato plant may contribute also to the disorder.
Since calcium is transported only in the water-conducting tissues, when water is reduced, calcium uptake is diminished. Under stress conditions, the plant will transport water to its leaves by transpiration, and since fruit does not transpire as much, calcium never reaches it. Because calcium has to be taken from the soil through the root system, calcium spray on the leaves and fruit are ineffective in preventing bloom rot.
You must provide a minimum of 1 inch of water per week for your tomatoes if Mother Nature does not. Around 2 inches per week is required when larger fruit is on the vine. Water at the ground level for best results.
Learn about this disorder, along with tomato disease prevention and care throughout the season at Eric Barrett’s Totally Tomato Program on July 16. For details, visit http://go.osu.edu/totallytomatoes.
Read the fact sheet about this disease at http://go.osu.edu/endrot. Other factors that will contribute to poor uptake of calcium are water stress, excessive salinity, root damage, low temperatures and fluctuations of moisture, infectious diseases and high nitrogen fertilizers.
Blossom end rot can also be reduced by avoiding severe pruning, keeping water levels uniform and regular, mulch to retain a soil temperature about 45 degrees around the plant, help transpiration by protecting from wind, soil test for a ph of 6.5, and remove affected fruit from the plant.