Strawberry anthracnose

The pathogen produces conidia, which are spores that spread primarily through water splashing during rain or overhead irrigation. These spores can survive on infected plant debris, in the soil, and on alternative host plants.

The fungus is known for its ability to remain latent in plant tissues, meaning it can be present without showing visible symptoms until the plant experiences stress or favorable environmental conditions occur.

Once the spores land on a susceptible surface, they germinate and penetrate the epidermis using specialized structures called appressoria. This allows the fungus to bypass the plant's physical defenses and invade internal tissues.

Genetic diversity within Colletotrichum species makes it a challenging pathogen to manage, as it can quickly adapt to different chemical treatments and environmental variations.

Symptoms of strawberry anthracnose can appear on all plant parts, including leaves, stems (petioles), crowns, and fruit. On stems and runners, dark, sunken, water-soaked lesions are the most common early indicators.

On the foliage, small, irregular necrotic spots with a reddish-brown margin may develop. These lesions can cause the leaf to curl and wither if the infection becomes systemic or reaches a severe level.

The most devastating symptoms appear on the fruit. Small, circular, sunken lesions develop on both green and ripe berries. These spots darken as the disease progresses and eventually become covered in pinkish spore masses.

Infected berries eventually turn into hard, dry, mummified fruits. These fruits remain on the plant or fall to the ground, serving as a continuous source of inoculum for the rest of the season.

• Sunken dark lesions on runners and petioles.
• Sunken circular spots on strawberry fruit.
• Pinkish or salmon-colored spore masses on infected tissue.

High relative humidity and warm temperatures are the primary drivers of Colletotrichum simmondsii outbreaks. The fungus thrives in moist environments, especially during periods of prolonged rainfall.

Temperatures ranging from 20°C to 30°C (68°F–86°F) are considered optimal for the rapid germination and colonization of the fungus within the strawberry tissues.

Poor field management, such as planting too densely, restricts airflow and keeps the foliage damp for longer periods, which significantly favors the spread of the pathogen.

Overhead irrigation, especially if performed in the late afternoon or evening, keeps the plants wet throughout the night, providing the ideal setup for fungal spore development.

Mechanical injuries caused by insects or field equipment create wounds that act as easy entry points for the pathogen to infect the plant.

Anthracnose is one of the most economically damaging diseases in strawberry production. It can destroy the entire crop if environmental conditions are conducive to disease spread during the fruiting phase.

Besides immediate yield losses, systemic infections can lead to the death of the entire plant crown, necessitating costly replanting of entire fields earlier than anticipated.

Infected nursery stock is a major concern, as it serves as a vehicle for introducing the pathogen into clean fields, leading to long-term contamination of the growing area.

The fruit marketability is severely reduced, as infected berries are visually unappealing and may rot rapidly during storage and transportation, leading to significant post-harvest losses.

The economic burden is further increased by the necessity of frequent fungicide applications and the potential loss of premium market status for the farm's produce.

The most effective strategy is the use of disease-free, certified nursery plants. Always inspect new planting material for any signs of lesions or discoloration before introducing it to the field.

Cultural practices are paramount: maintain clean fields by removing and destroying symptomatic plant parts and debris. Improve airflow by managing planting density and controlling weed growth.

Incorporate a rigorous fungicide spray program, specifically during the flowering and fruit development stages, which are the most susceptible periods for infection.

Rotate the use of fungicides with different modes of action to manage the risk of the pathogen developing resistance to common chemical treatments.

Consider using drip irrigation instead of overhead irrigation to keep the foliage and fruit dry, thereby reducing the environmental suitability for fungal spore germination and spread.