Q: What are some common diseases and pests that affect tomatoes? How can I avoid these problems?
A: Weather fluctuations from warm to cold and back again, plus a lot of rain, create perfect conditions for tomato diseases.
- Septoria leaf spot is common in cold weather. You may avoid this problem by planting after the weather has settled, around Memorial Day. Pick off affected leaves as they appear.
- Tomato early and late blight are serious diseases that occur in warm, wet weather. These diseases affect leaves, stems and fruit, and in the case of late blight, may kill plants within a few days. Choose resistant varieties whenever possible, rotate plantings, space plants to increase air circulation and avoid wetting leaves during irrigation. Contact your county Cornell University Cooperative Extension office for a list of resistant or tolerant varieties, diagnosis and treatment.
- Blossom end rot (a dark spot at the bottom end of the fruit), cat-facing and blossom tear (distorted fruit) are physiological problems that are watering- and weather-related. Blossom end rot is caused when uneven watering affects the ability of the plant to get the necessary calcium out of the soil. Maintain uniform moisture through drip irrigation, mulching and attention to the soil moisture, especially in hot temperatures.
- Blossom tear and cat-facing are more prevalent when wet, cool weather prevails during the flowering period
- My top insect pest is the tomato horn worm. This green caterpillar with white stripes may reach 3 to 4 inches in length and sports a black horn at its rear. The mature moth is often called the “hummingbird moth” as it resembles a mini hummingbird in flight. The caterpillars are large enough to be removed by hand although they are well camouflaged. If you see many small cocoons on the back of a caterpillar, leave it alone — it is infested with tiny predatory wasps and will it will not survive long.
- Aphids are my No. 2 tomato pest. Large populations of aphids are easily reduced with a firm but non-damaging stream of water. Ladybugs favor a diet of aphids as do many other predatory insects. Attract these beneficial insects to your yard with nectar- and pollen-producing flowers. Many herbs have the small flowers that many of these beneficial herbs prefer. (Go to this website for 10 Ways to Control Aphids Organically)
- Cutworms are rare for me, but not for other people. These caterpillars feed on the stems of seedling tomatoes; exclude them by placing a collar of cardboard or plastic around the plant’s stem base.
— Rob Somma, Stony Point master gardener, with Amy Albam, senior horticulturist, Cornell Cooperative Extension of Rockland
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