Brown spots on cherry tomatoes are a common issue for home gardeners, often causing concern. Understanding the causes behind these blemishes is crucial for maintaining healthy plants and a productive harvest.
Identifying Common Causes
Blossom end rot is a common cause, appearing as a sunken, leathery brown or black patch at the fruit’s bottom. This physiological disorder links to inconsistent watering and the plant’s inability to move calcium to developing fruits. Rapid growth and excessive nitrogen fertilizers can also contribute.
Fungal diseases also cause brown spots, distinct from blossom end rot. Early blight creates dark, concentric rings on the fruit, resembling a target pattern. Anthracnose causes small, sunken, water-soaked spots that may later develop black fungal structures. These infections thrive in moist, humid conditions and spread through water splashing from infected soil.
Bacterial diseases also cause distinct spots. Bacterial speck results in very small, dark, raised spots that may have a greasy or translucent appearance. Bacterial spot can cause small, dark, angular lesions. Unlike fungal diseases, bacterial spots often appear more numerous and can cause leaves to yellow and drop.
Sunscald, like a sunburn for tomatoes, occurs from overexposure to intense sunlight, especially during hot, dry weather. The affected area appears as a bleached, white, or yellowish patch that eventually turns papery, brown, or gray and sunken on the sun-facing side. This is common if foliage is lost due to disease, pests, or over-pruning, leaving fruit vulnerable.
Pest damage can also cause brown spots. Insects like stink bugs feed on fruit, leaving small, discolored, or sunken spots where they pierce the skin. These feeding sites can create entry points for secondary infections. Tomato fruitworms chew deep holes, often near the stem end, leading to decay.
Effective Solutions for Each Cause
For blossom end rot, ensure consistent soil moisture. Deep, regular watering helps the plant transport calcium to the fruit more effectively. Maintaining steady soil moisture is often the most impactful solution, even more than soil calcium amendments. Remove any affected fruit, as it will not recover.
For fungal diseases, promptly remove and dispose of any affected leaves or fruit to prevent further spread. Improving air circulation by careful pruning helps dry foliage, making it less hospitable for fungal growth. Applying an appropriate fungicide can help manage infection if used at the first sign of disease.
Bacterial diseases are challenging to treat once established. Focus on sanitation by removing infected plant parts and avoiding overhead watering, which can spread bacteria through splashing water droplets. Sterilizing pruning tools after use also prevents cross-contamination.
If sunscald is present, provide immediate shade to the exposed fruits. This can be achieved using shade cloth or by allowing more foliage to grow to naturally cover the developing tomatoes. While the damaged fruit will not heal, protecting unaffected fruit from further exposure can prevent new spots from forming.
For pest damage, identify the specific pest causing the issue. Hand-picking larger pests like hornworms is an effective immediate measure. For smaller insects, a strong spray of water can dislodge them. If infestations are severe, organic insecticidal sprays or biological controls may be necessary, targeting the specific pest while minimizing harm to beneficial insects.
Strategies for Prevention
Consistent watering is paramount for preventing many cherry tomato problems, especially blossom end rot. Tomato plants need regular, deep hydration, typically 1 to 2 inches of water per week. Watering at the plant’s base with drip irrigation or a soaker hose delivers water directly to roots and keeps foliage dry, discouraging disease.
Proper soil health provides a strong foundation. Cherry tomatoes thrive in well-draining, nutrient-rich soil with a pH between 6.0 and 6.8. Incorporating organic matter like compost or aged manure improves soil structure and nutrient availability. Balanced fertilization, with lower nitrogen and higher phosphorus and calcium, supports healthy fruit development and reduces blossom end rot risk.
Adequate air circulation and strategic pruning minimize fungal and bacterial issues. Spacing plants appropriately (2-3 feet apart for indeterminate varieties) and using stakes or trellises keeps foliage off the ground, promoting airflow. Pruning lower leaves that touch the soil reduces disease splash, but avoid excessive pruning that exposes fruit to sunscald.
Providing appropriate sun protection is crucial, especially in regions with intense summer heat. While tomatoes need ample sunlight (6-8 hours daily), excessive exposure leads to sunscald. Using shade cloth during the hottest parts of the day or planting varieties with dense foliage offers natural protection.
Pest management involves regularly inspecting plants for early pest signs. Addressing small infestations promptly prevents them from becoming severe. Encouraging beneficial insects, which prey on common tomato pests, reduces the need for chemical interventions.
Selecting disease-resistant cherry tomato varieties significantly reduces many common problems. Varieties labeled with resistance codes for specific fungal or bacterial diseases perform better in challenging conditions. Choosing crack-resistant varieties also helps, as cracks can be entry points for pathogens.