Strawberry Anthracnose: A Threatening Disease
Strawberry Anthracnose is a lethal disease that affects strawberries. It poses a danger to all parts of the plant, including the fruit, crowns, leaves, petioles, and runners. The pathogen responsible for this disease is associated with three species of the fungus Colletotrichum: C. acutatum, C. gloeosporioides, and C. fragariae. Among these species, C. acutatum is the primary culprit.
Cycle of Strawberry Anthracnose
The primary source of anthracnose infection enters the fields through strawberry transplants.
Pathogen Growth and Spore Production
The pathogen has the ability to grow in green tissue without displaying any symptoms. It can remain dormant or produce spores. Once the green tissue dies, the fungus becomes active and generates numerous spores. C. acutatum can survive in the soil, on infected plants, and plant debris such as old dead leaves and mummified fruit. It can also infect weeds growing alongside the strawberry fields.
Spread and Infection
Warm, humid weather and rainfall create favorable conditions for spore production, germination, and infection. The spores are dispersed through splashing rain, wind-driven rain, or through human activity and equipment movement in the field. It is important to note that these spores are not airborne and cannot spread over long distances through the wind.
Germination and Rapid Disease Development
Spores require free water on the plant surface to germinate and initiate infections. The disease can develop rapidly, with up to 90% of the fruits becoming infected within a week or even less.
Signs and Symptoms of Strawberry Anthracnose
Targeted Plant Parts
The fungus can attack various parts of the strawberry plant, including the fruit, runners, petioles, and crown.
Lesions and Wilting
Dark elongated lesions develop on petioles and runner stems. These lesions can girdle the affected parts, causing individual leaves or entire daughter plants to wilt and eventually die. Under warm and humid conditions, salmon-colored masses of spores may appear on the surface of the lesions.
Infected flowers may die and dry out. If infection occurs shortly after pollination, the developing fruit remains small, hard, and misshapen.
When the crown tissue is infected, crown rot may develop, leading to the wilting and death of the entire plant. Upon sectioning infected crowns, the internal tissue appears firm and ranges in color from reddish-brown to dark brown. The crown tissue may exhibit uniform discoloration or streaking with brown.
Fruit Lesions and Mummification
Whitish, tan, or light-brown water-soaked lesions form on the fruit. These lesions eventually turn brown or dark brown, becoming sunken and enlarging within two to three days to cover most of the fruit. The lesions are often covered with pale-orange or salmon-colored spore masses. In moist conditions, the fungus may grow around the edges or through the lesions, giving them a fuzzy appearance. Infected fruit dries down and shrivels, resulting in hard, black, mummified fruit. The disease can affect the fruit at any stage of development.
The pathogen can also spread to the root zone, causing black lesions on the roots. Infected tips can lead to widespread infections on young tissue of the plug plants, leading to plant loss.
Management of Strawberry Anthracnose
To prevent and eradicate strawberry anthracnose disease, the following fungicides are recommended:
- RANSOM 600WP: Mix 15 g in 20 liters of water
- DUCASSE 250 EW: Mix 20 ml in 20 liters of water
- ABSOLUTE 325 SC: Mix 10 ml in 20 liters of water
Implement the following measures to control the disease without using chemicals:
1. Use disease-free planting material.
2. Plant resistant varieties.
3. Avoid overhead irrigation if possible and opt for drip irrigation to keep the crop dry.
4. Mulch with straw to reduce water splashing and disease spread.
5. Remove infected plant parts to prevent them from serving as a source of disease.
6. Avoid working in the garden when plants are wet and disinfect all garden tools after use to prevent the spread of the disease.
7. Do not compost infected plants or plant parts. Thoroughly clean garden areas in the fall, after harvest, to reduce overwintering sites for fungal spores.
8. Ensure proper spacing between plants to facilitate air movement within the crop.
For improved efficacy of the fungicides, mix them with INTEGRA (3ml/20l). INTEGRA acts as a sticker, spreader, wetter, and penetrant.
To prevent the fungus from developing resistance, alternate the use of different fungicides throughout the plant’s growing season.
Timely disease control is crucial.
Maintaining proper nutrition activates the crop’s defense system against infections.