System Article
Podosphaera aphanis, also known as strawberry mildew, is a powdery mildew that grows on strawberries. You can identify powdery mildew by curled leaf margins and fine white fungal mycelium on the underside, as well as irregular light purple spots. The powdery mildew can cause major economic damage.
#Strawberries
Overview Strawberry Powdery Mildew Fruit Disease is caused by the fungus Podosphaera aphanis. This disease affects the fruit, leaves, and flower parts of strawberry plants, leading to reduced fruit quality and yield losses. It is particularly problematic in environments with high humidity and moderate temperatures. Symptoms 1. Fruit Symptoms: o Powdery Growth: Infected fruit develops a white, powdery fungal growth on its surface. This growth resembles a dusty or cobweb-like layer. o Fruit Deformation: The disease can cause the fruit to become deformed, misshapen, or have a rough texture. o Premature Decay: Affected fruit may ripen prematurely and become soft and shriveled. 2. Leaf Symptoms: o Powdery Spots: On leaves, the disease starts as small, white, powdery spots on the upper surface. These spots can coalesce into larger areas of powdery growth. o Leaf Curling: Severely infected leaves may curl, distort, or become brittle. 3. Flower Symptoms: o Blossom Infection: Flowers can also be infected, showing white, powdery growth on the petals and sepals. Infected blossoms may fail to develop into fruit.
Disease Cycle 1. Inoculum Source: The fungus Podosphaera aphanis overwinters in plant debris and on infected plant parts. It produces conidia (asexual spores) that serve as the primary source of inoculum for new infections. 2. Spore Release: During favorable conditions, the fungus releases conidia into the air. These spores are dispersed by wind and can infect healthy plants. 3. Infection: Spores land on plant surfaces and germinate under high humidity conditions. The fungus then infects the plant through natural openings or directly through the leaf surface. 4. Disease Development: Once established, the fungus grows and spreads, producing more spores that infect other parts of the plant and neighboring plants. 5. Spore Dissemination: As the infected plant parts decay, they release more spores into the environment, further spreading the disease. Favorable Conditions • High Humidity: The disease thrives in environments with high humidity and prolonged leaf wetness. • Moderate Temperatures: Podosphaera aphanis prefers moderate temperatures, typically between 60°F and 75°F (15°C to 24°C). • Dense Planting: Crowded plantings and poor air circulation increase humidity around the plants, creating ideal conditions for the disease.
Management Strategies 1. Cultural Practices: o Proper Spacing: Space plants adequately to improve air circulation and reduce humidity around the leaves and fruit. o Pruning: Remove and destroy infected plant debris and leaves to reduce the inoculum source. o Avoid Overhead Irrigation: Use drip irrigation to minimize moisture on the plant surfaces and reduce the risk of infection. o Crop Rotation: Rotate strawberries with non-host crops to minimize fungal buildup in the soil. 2. Sanitation: o Remove Debris: Regularly clean up plant debris and fallen fruit to reduce sources of fungal spores. o Disinfect Tools: Use disinfected tools to prevent the spread of the disease from one plant to another. 3. Fungicide Applications: o Preventive Sprays: Apply fungicides as a preventative measure during conditions favorable to powdery mildew development. Common fungicides include those with active ingredients such as sulfur, fenarimol, or myclobutanil. o Rotate Fungicides: Rotate between different classes of fungicides to reduce the risk of resistance development. 4. Resistant Varieties: o Variety Selection: Some strawberry varieties have partial resistance to powdery mildew. Consult local extension services or nurseries for information on resistant varieties. 5. Monitoring and Timing: o Regular Inspection: Regularly inspect plants for early signs of infection and take action promptly to prevent the spread of the disease. Conclusion Strawberry Powdery Mildew Fruit Disease, caused by Podosphaera aphanis, can significantly impact strawberry production by affecting fruit quality and reducing yields. Understanding the disease cycle and implementing a combination of cultural, sanitation, and chemical control measures are essential for managing and reducing the impact of this disease. By maintaining good practices and monitoring plants regularly, growers can protect their strawberry crops and ensure a healthy, productive harvest.
