Top 10 Tomato Pests and Problems

1. Tomato Hornworms

Hornworms can kill a mature tomato plant in a single night. These large green worms are about 2-3 inches (5-8 cm) long and have little horns on their heads. They’re hard to spot, since they’re camouflaged to look just like the plant’s stem. To prevent hornworms, we recommend you plant marigolds around your tomatoes because their strong scent repels hornworms. To treat a current infestation, try a product like Safer® Caterpillar Killer, which won’t harm your friendly earthworm population.

2. Cracking Fruit

When cracks appear on your ripe tomatoes, it’s probably due to hot, rainy weather after a spell of dry conditions. When it’s not raining, water your tomatoes consistently during the growing season so they don’t get too thirsty and soak up all the rainwater during a downpour.

3. Cat-facing

If your tomatoes are oddly deformed with ripples, bumps and lumps, they were probably pollinated in temperatures that were too cool. When possible, plant your tomatoes a little later in the season, when the nighttime temperatures are between 55 and 75 F (13-24 C).

4. Blossom End Rot

Blossom end rot causes black spots on the bottoms of the tomatoes as they ripen. This is caused by a lack of calcium. Many garden centers sell soil test kits and additives, such as lime or gypsum, to add to the soil.

5. Blossom Drop

If your tomato blossoms fall off the plant before tomatoes can develop, it’s likely due to cool temperatures. Tomatoes need the temperature to be between 55 and 75 F (13-24 C) at night to develop properly.

6. Sun Scald

Yellow patches that form on the tomato skins eventually turn thin and white and affect the taste of your tomatoes. This is sun scald, and you can prevent it by using tomato cages or other support systems to surround the plants and prop up the branches, which will provide shade for the fruit.

7. Low Yield

If your plant isn’t producing many tomatoes, and the ones that do grow are small and tasteless, you may have too much nitrogen in the soil, or your plants may be too close together, preventing optimum airflow. Test your soil with a kit from your neighborhood garden center, and follow the recommendations given for adding nitrogen. Plant your tomatoes at least 2 feet (.6m) apart so the wind can pollinate the flowers.

8. Leafroll

If your mature tomato plant’s leaves start curling, the culprit is probably high temperatures, wet soil or too much pruning. Rest assured leafroll won’t affect the development of your tomatoes, but be careful not to over-prune and make sure your soil has optimum drainage.

9. Bacterial Canker

Bacterial canker often starts as yellow dots on ripening tomatoes. If you look closely, you’ll see a dark rim around each spot. This problem occurs naturally, and to treat it, you’ll need to remove the infected plant right away so it doesn’t spread to other plants. Throw away the infected plant and don’t add it to your compost. To prevent bacterial canker, rotate your crops each year.

10. Early Blight

Early blight is caused by a fungus that lives in the soil over the winter and appears on the leaves as brown spots with rings around them. Early blight can be treated with a garden fungicide that you can get at your local garden center. Rotating your plants each year will help prevent early blight.