Tomato plants can be susceptible to various diseases and pests, but with proper care and preventive measures, you can keep them healthy. On our previous 2 blogs about tomatoes, we have tried to cover growing tomatoes from seed to harvest and on our final blog about the subject, we will talk about common diseases and pests you have to watch out for as a fellow gardener.
Common Tomato Diseases
Early Blight (Alternaria solani)
Identification: Dark spots appear on lower leaves, which eventually turn yellow and cause defoliation. The spots may have concentric rings.
Prevention: Rotate crops yearly to prevent the buildup of pathogens in the soil. Mulch around plants to reduce soil splash onto leaves. Water at the base of the plants to keep foliage dry. Remove and destroy infected plant parts.
Late Blight (Phytophthora infestans)
Identification: Large, water-soaked spots on leaves, which quickly enlarge and become brown and papery. White fungal growth may be present on the undersides of leaves in humid conditions.
Prevention: Provide good air circulation by spacing plants adequately. Avoid overhead watering. Remove and destroy infected plants immediately to prevent spread.
Fusarium and Verticillium Wilt
Identification: Plants show wilting, yellowing, and eventually death. Cutting stems may reveal brown discoloration in the vascular tissue.
Prevention: Plant resistant tomato varieties when possible. Practice crop rotation to reduce soil-borne pathogens. Ensure good drainage and avoid overwatering.
Common Tomato Pests
Tomato Hornworm (Manduca quinquemaculata)
Identification: Large green caterpillars with white diagonal stripes and a horn-like projection on the rear end. They can defoliate plants rapidly.
Prevention: Handpick and destroy hornworms when you see them. Attract natural predators like parasitic wasps by planting flowers such as marigolds and dill.
Aphids
Identification: Small, soft-bodied insects that cluster on new growth, sucking sap from plants. They can be green, black, brown, or red.
Prevention: Spray plants with a strong stream of water to dislodge aphids. Introduce natural predators like ladybugs and lacewings. Neem oil or insecticidal soap can also be used as organic control methods.
Tomato Fruitworm (Helicoverpa zea)
Identification: Caterpillars feed on tomato fruit, causing surface damage and sometimes tunneling inside.
Prevention: Monitor plants regularly and handpick any caterpillars found. Use row covers to prevent adult moths from laying eggs on plants. Apply Bacillus thuringiensis (Bt) if infestation is severe.
Whiteflies
Identification: Tiny, white, moth-like insects found on the undersides of leaves, producing honeydew that leads to sooty mold growth.
Prevention: Introduce natural predators like parasitic wasps and predatory beetles. Use reflective mulches and yellow sticky traps to deter whiteflies.
Tuta absoluta (Tomato Leafminer)
Identification: Keep an eye out for small yellowish-green caterpillars tunneling into leaves, stems, and fruits.
Prevention: Implement strict monitoring. Remove and destroy infected plant parts. Utilize biological control methods such as introducing natural predators. Consider using insecticides if infestation is severe, rotating between different classes to prevent resistance.
Prevention and Management
Monitoring: Regularly inspect tomato plants for signs of infestation, including color or foliage changes, mines in leaves, frass (insect waste), and larvae.
Cultural Practices: Remove and destroy infected plant parts to reduce the population. Practice crop rotation to disrupt the lifecycle of the pests. Practice good garden and tool hygiene to prevent the spread of diseases.
Biological Control: Encourage natural predators such as certain parasitic wasps and predatory beetles like lacewings or ladybugs that prey on pests.
Chemical Control: If infestation is severe, consider using proper fungicides or insecticides labeled for your needs. However, be cautious to follow instructions carefully and consider the potential impact on beneficial insects and the environment. Rotate between different classes of fungicides or insecticides to prevent resistance buildup.
Integrated Pest Management (IPM): Implement a combination of cultural, biological, and chemical control methods as part of an integrated pest management approach.
Resistant Varieties: Consider planting resistant varieties if available in your region.