AUGUST
2009

 

 

By
B. Rosie Lerner
 
Purdue Extension
Consumer
Horticulturist

 

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08-20-09

Blossom-End Rot of Tomatoes Likely This Season

Eager tomato-growers having lovingly nurtured seed to fruit have anxiously awaiting their first ripe gem. But, alas, a black leathery spot appears at the base of the fruit.

Blossom-end rot is thankfully not an infectious disease but a frustrating disorder of the fruit. The black scar tissue thought to be caused by a deficiency of calcium in the developing fruit is usually brought on by extreme fluctuations in soil moisture. This year we sure had extremes of rainfall, so blossom-end rot is likely to be prevalent.

The spot develops on the blossom end of the fruit opposite the point of stem attachment, thus the name blossom-end rot. The scar is usually firm and leathery, although secondary rot organisms may enter through the damaged tissue, causing a soft rot to develop.

Tomatoes are the species most frequently affected by blossom-end rot, but peppers, summer squash and other cucurbit plants can also be afflicted.

There is no spray that will control blossom-end rot except maybe from the irrigation hose. Some folks recommend spraying the plants with calcium, but by the time you see the scar on the fruit, it is too late. Most Indiana soils have plenty of calcium, although some sandy soils may be deficient.

 Although the fruits that have already developed the scar cannot be helped, the new developing fruits can be. Watering during dry spells and mulching to conserve soil moisture will help reduce the fluctuations in soil moisture and thus encourage steady growth and calcium supply in the fruits.

 

 

Writer: B. Rosie Lerner
Editor: Olivia Maddox