Common leaf spot
Mycosphaerella fragariae
Also Known As - Leaf spot CommonWhat is a Common leaf spot (Mycosphaerella fragariae)?
Common leaf spot is a fungal disease caused by Mycosphaerella fragariae (anamorph=Ramularia tulasnei) that affects strawberry plants. Infected plants display small, deep purple spots on the upper surface of leaves. As the disease progresses, these spots enlarge to 0.125 to 0.25 inches (3–6 mm) in diameter. The center of the spots turns brown, then gray to white depending on leaf age and environmental conditions. In severe cases, the spots may merge and kill the leaves. Elongated lesions can also develop on petioles, stolons, calyxes, and fruit trusses.
How does Common leaf spot (Mycosphaerella fragariae) occurs?
The fungus overwinters on infected leaves and as sclerotia. During moist weather conditions, conidia are abundantly produced in lesions on infected leaves. These conidia are then spread to healthy tissues through rain-splashing. The disease cycle continues as the conidia germinate on susceptible young leaf tissue, leading to new infections. Long wet periods and warm temperatures create favorable conditions for disease development, particularly in the spring and fall.
Symptoms
1 - Effects on Plants
• Common leaf spot weakens plants by damaging leaves, reducing photosynthesis, and impacting overall plant vigor. • Severe infections can lead to defoliation, reducing energy production and affecting fruit quality and yield. • Fruit infections (black seed disease) result in hard, leathery spots, impacting appearance and market value.
Solutions
1 - Cultural Practices
• Use disease-free planting stock to reduce initial inoculum. • Maintain good plant hygiene by removing and disposing of infected leaves and plant debris after harvest. • Practice crop rotation to reduce disease buildup in the soil. • Choose planting locations with optimal environmental conditions that are less conducive to disease development. • Use drip irrigation or water at times that promote rapid drying of foliage to minimize leaf wetness.
2 - Biocontrol Agents
• Bacillus subtilis: Commercial products such as Serenade ASO and Serenade Optimum contain this beneficial bacterium that can suppress common leaf spot. • Trichoderma spp.: Trichoderma-based products like Root Shield Plus WP and Trichodex are effective in controlling fungal diseases, including common leaf spot.
3 - Chemical Control
• Several fungicides with brand names are available including Bravo Weather Stik (chlorothalonil), Rally 40W (myclobutanil), Captan 80 WDG (captan), and Cuprofix Ultra 40 Disperss (copper-based) azoxystrobin + difenoconazole (Quadris Top), and iprodione (Rovral) are also commonly used to manage the disease. • It is important to follow the instructions on the product label for proper application and safety precautions. Consult with local agricultural experts or extension services for specific brand recommendations based on your region and local regulations.
