ROANOKE TIMES
Copyright (c) 1996, Roanoke Times
DATE: Sunday, July 7, 1996 TAG: 9607090012
SECTION: HOMES PAGE: D-2 EDITION: METRO
COLUMN: Dear John
SOURCE: JOHN ARBOGAST
Every summer, many gardeners notice that their first tomatoes of the season have developed a brown discoloration on the end of the fruit opposite the stem. It's commonly known as blossom end rot.
The name describes the results, even though the brown area is hard and dry at first and not the typical soft type rot. Blossom end rot is not a disease in the usual sense since it is not caused by a fungus, bacteria or virus. That's bad news for gardeners because it means there is no point in applying unnecessary disease-control sprays.
It is caused by unfavorable growing conditions, principally a lack of, excessive, or fluctuating soil moisture resulting in a lack of calcium uptake from the soil to the developing fruits.
The rot occurs frequently on tomato plants that were grown under favorable conditions early in the season but have been subjected to drought during the early stages of fruit development.
The problem is worse during the first part of the production season because the plants have been growing rapidly during that time and using more calcium for the vine and leaves and leaving less for the fruit. As the growth slows later in the season, the problem usually diminishes. The heavy spring moisture this year did not eliminate the problem since early excessive soil moisture can injure root hairs, making it easier for the rot to occur when temperatures get hot.
Veteran gardeners can explain to new gardeners how the characteristic tomato rot starts as a small dot or area of brown discoloration on a green tomato, then enlarges and darkens until the bottom one-third or more of the surface is involved. The tomato develops a strange shape as the brown area becomes flattened or concave during the fruit ripening period.
While no fungicide sprays help, calcium sprays that have been sold in a ready-to-use container might be helpful in reducing the rot by adding calcium directly to the young fruits.
Important controls are: regulate the moisture supply in the soil. The garden should be well-drained. If drought occurs, hoeing or cultivation should be very shallow to reduce soil water loss and should not be done close to the plants to avoid root pruning. Encourage only moderate tomato growth. Use a fertilizer low in nitrogen and high in phosphate, such as 5-10-5 or 5-10-10. Take soil tests from the garden at the end of season to see if calcium is needed. Note that plenty of calcium in the garden soil does not mean that the plants will be able to take it up, though. Water (the soil, not the plants' foliage) deeply when hot, drying winds are blowing.
Daily watering will likely keep the soil too wet. Leaf rolling on tomatoes is a common sign of too much moisture. Mulch tomatoes to maintain an even soil moisture level.
For fast answers to your horticulture questions, call the direct number of the Master Gardeners Greenline in the Roanoke Extension Office at 857-6208.
Send short questions about your lawn, garden, plants, or insects to Dear John, c/o The Roanoke Times, P.O. Box 2491, Roanoke, Va. 24010-2491. We need your mail, but this column can't reply to all letters. Those of wide appeal will be answered during the weeks that the subject is timely. Personal replies cannot be given. Please don't send stamps, stamped envelopes, samples or pictures.
Gardener's checklist
Jobs for second week of July.
Scout for the active presence of "azalea lacebugs" bleaching out the green color of azalea foliage by flipping some of the leaves over before you spray. Recommended controls for active lacebugs are Orthene and diazinon.
Check potato rows and protect all shallow tubers from light by covering with soil or mulch. Root cuttings from the vigorous new growth of indoor plants.
LENGTH: Medium: 72 linesby CNB