Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: THURSDAY, July 29, 1993 TAG: 9307280109
SECTION: CURRENT PAGE: NRV-6 EDITION: NEW RIVER VALLEY
SOURCE: Joe Hunnings
DATELINE: LENGTH: Medium
Let's look at a few common tomato problems that you may be experiencing or have experienced.This should help you identify, prevent and control these problems.
Poor fruit set
\ Symptoms: Plants are healthy and vigorous, but no fruit develops. There are several possible reasons.
\ Analysis: 1. Extreme temperatures - below 55 degrees or above 90 degrees - cause the blossoms to drop. 2. Dry soil causes blossoms to dry and fall. 3. Shading reduces the number of blossoms produced. Tomatoes need more than six hours of direct sunlight. 4. Excessive nitrogen promotes leaf growth at the expense of blossom and fruit formation.
\ Solutions: Plant tomatoes at the proper time of year in an area that receives sufficient sunlight, and water tomatoes regularly. Mulch is important in managing water stress. Follow fertilizer recommendations available from your local Cooperative Extension Service office.
Blossom-end rot
\ Symptoms: A round, sunken area on the bottom of the fruit that turns brown to black and feels leathery.
\ Analysis: Blossom end rot is a physiological disease apparently caused by a temporary shortage of calcium. It is aggravated by extreme fluctuations in soil moisture, excess soil salts or cultivating too close to the plant roots.
\ Solutions: Maintain uniform moisture with mulch and supplemental irrigation. Avoid excessive nitrogen applications, particularly in the ammonium form. A timely and repeated spray of two tablespoons of calcium chloride per gallon of water has been reported to prevent blossom end rot. The first fruit are usually most severely affected.
Early blight
\ Symptoms: Irregular brown spots with concentric rings on the lower leaves. Usually there is a yellowing of the tissue around each spot. The spots will enlarge, causing the leaf to turn brown and drop off.
\ Analysis: This disease is caused by a fungus carried on tomato seeds, transplants or on plant debris in the soil.
\ Solutions: Once again, mulch can help by acting as a barrier to prevent splashing of spores from the soil to the foliage. When watering, be careful not to wet foliage in the late afternoon. Long periods of leaf wetness enhance disease development. Annual rotations with plants not belonging to the tomato family will reduce the disease incidence. If treatment is necessary use a fungicide such as Chlorothalonil, especially after warm, humid periods.
Late blight
\ Symptoms: Bluish-gray water soaked patches appear on the leaves, eventually shrivelling and turning brown. Similar spots appear on stems and fruit.
\ Analysis: This is a fungus disease that is very destructive, as most of us found out last year. The fungus is most active in wet weather with cool nights and warm days. (Remember last summer?)
\ Solutions: Cultural control involves removing and destroying all infected tomato debris from the garden. Composting the debris is not even a good idea. Rotations, rotations, rotations. Be especially careful to avoid planting tomatoes after potatoes. Chlorothalonil will provide control if used every seven to 10 days during periods that encourage disease development or where symptoms have been observed.
Aphids
\ Symptoms: Leaves turn yellow and may be curled, distorted or puckered. Pale green, yellow or purple soft-bodied insects are found on the stems and undersides of leaves.
\ Analysis: In small numbers, aphids do little damage. However, populations can build up rapidly to damaging levels. Aphids suck juices from tomato leaves and spread diseases.
\ Solutions: Healthy, well-cared-for plants and soils will have minimal problems with aphids (or any other problem for that matter). Natural enemies are also helpful in reducing aphid problems. In extreme cases, gardeners may use a forceful spray of water, insecticidal soap or Malathion.
by CNB