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LANDSCAPING | GARDENING | PROBLEM SOLVING

Tomato Problems

Tomato problems can be broken down into 2 types: Fungal Diseases and Physiological Problems.

When buying transplant tomatoes, be sure to pick out healthy plants with no yellowing or speckling on the leaves (could be fusarium or leaf spot). If you're not sure what tomatoes you want or need, checking the tag can be a big help in selecting a good tomato. Look for a string of letters on the tag. They denote resistance to disease:

  • A - Alternaria leaf spot
  • F - Fusarium wilt
  • FF - Race 1 & Race 2 Fusarium
  • L - Septoria leaf spot
  • N - Nematodes
  • T - Tobacco mosaic virus
  • V - Verticillium wilt

Improper watering can cause many problems for growing tomatoes. It is best to water deeply and regularly while the plants are developing. Irregular watering, (missing a week and trying to make up for it), leads to blossom end rot and cracking. Once the fruit begins to ripen, lessening the water will coax the plant into concentrating its sugars. Don’t withhold water so much that the plants wilt and become stressed or they will drop their blossoms and possibly their fruit.

Here are the basic problems associated with each type.

Disease / Description

Preventive Measures

Chemical Treatments

Early Blight
(Alternaria solani)

Spots develop on older leaves first and are irregularly shaped with "target like" concentric rings of infection' spots are brown and vary in size. Spots can coalesce and leaves might turn yellow, dry up and fall. Symptoms can also occur on stems as well as the fruit.

  • Maintain good soil fertility. Apply a pre-plant fertilizer once more after the first tomatoes set on the vines

  • Deep-till in the fall to bury debris that harbors disease spores

  • Rotate tomatoes out of the area for 3 - 4 seasons

Chlorothalonil is approved to treat this disease. For best results, begin application shortly after planting established plants. Applications should be made every 7 - 10 days, depending on label instructions. Severe infections won't respond to fungicide treatments.

Fusarium Wilt
(Fusarium oxysporum f. sp lycopersici)

Older leaves turn yellow and wilt, then fall .Yellowing might occur on only one side of the plant. Shoots wilt until the plant is dead. If the main stem is cut near the soil line, dark-brown streaks are evident running lengthwise. This discoloration often extends upward and is especially evident at the point where leaf petioles join them.

  • Maintain plant vigor with proper fertilization and irrigation

  • Control weeds

  • Clean up infected plant debris

  • Rotate tomatoes out of the area for 4 - 6 years; avoid planting related crops (potatoes, peppers, eggplant) during this time

There are no fungicides to treat this disease because it is soil-borne and systemic in the plant. Fusarium persists in the soil for several years.

Late Blight
(Phytophthora infestans)

Pale-green spots (that initially appear wet and often translucent) begin at the leaf tips and margins. Spots

Destroy volunteer tomatoes that come from past seed sources; they can serve as a source of disease spores. Chlorothalonil is approved to treat this disease. Apply if weather conditions favor disease development. Applications should be made every 7 - 10 days; follow label directions.

Verticillium Wilt
(Verticillium albo-atrum)

Older leaves turn pale green, yellow, wilt and might dry up and drop prematurely. V-shaped lesions appear at leaf tips. As leaves drop, the youngest leaves might curl upward at the edges. Internal stem tissue, especially low on the stem, might have a tan discoloration.

Infected plants usually survive the season but are stunted and tomatoes might be small and of low yield depending on the intensity of the attack.

  • Plant verticillium-resistant varieties

  • Maintain plant vigor with proper fertilization and irrigation

  • Control weeds

  • Clean up infected plant debris

  • Rotate tomatoes out of the area for 4 - 6 years and avoid planting related crops (potatoes, peppers, eggplant) during this time. Avoid planting strawberries and raspberries in the area, which are also susceptible

There are no fungicides to treat this disease because it is soil-borne and systemic in the plant. Verticillium persists in the soil for several years.