Nov 11, 2021

Louisiana strawberries hit by crown rot disease

Louisiana growers have not yet finished planting this year’s strawberry crop, and a disease called crown rot has already been detected in a commercial field.

This disease is caused by a soil-borne, fungal-like microorganism genus called phytophthora. Sometimes it is called water mold.

Phytophthora is known as “the plant destroyer.” The name originates from the Greek words phytón, meaning plant, and phthorá, meaning destruction.

Symptoms of crown rot begin with random wilting of plants in the field. Diseased plants may appear stunted compared to nearby healthy plants. These symptoms may resemble another root rot disease called red stele.

As the disease progresses, wilted plants become brown and die within a few weeks.

Cutting the crowns of wilted plants reveals a dark reddish-brown internal discoloration of the tissue. It’s important to note, however, that another disease called crown anthracnose caused by the Colletotrichum species may lead to similar discoloration.

The crown rot pathogen thrives in poorly drained, heavily compacted soils. Water-saturated soils and over-irrigation may predispose strawberry plants to phytophthora crown rot disease.

The pathogen can survive for several years in infested fields and can spread with irrigation water and movement of contaminated soils by farm equipment.

Successful crown rot disease management in home gardens and commercial strawberry fields requires an integrated approach. It begins with rapid and accurate identification of the cause of the problem. Symptomatic plants should be removed and properly discarded.

Start with clean, disease-free plants, and plant in well-drained, fertile soils. Avoid planting in fields with a history of disease. Prepare fields to break any hardpans, and plant in raised beds to provide adequate water drainage.

Good agricultural practices, including cleaning tools, may reduce the disease spread. Remove crop debris from the fields after harvest is completed.

Timely application of fungicides containing mefenoxam and metalaxyl as active ingredients in the fall in commercial fields through drip irrigation is effective in managing phytophthora crown rot. Repeating fungicide application during the rapid root growth period in the spring is also beneficial in combating this disease.

Follow the product label while handling and applying chemical pesticides. For complete, detailed information on use of fungicides, go to www.LSUAgCenter.com and search for the LSU AgCenter Plant Disease Management Guide.

– Raj Singh, Louisiana State University

Photo at top: An infected strawberry plant, left, showing reddish-brown internal discoloration of crown tissue (yellow arrow) and a healthy strawberry plant, right, exhibiting healthy crown tissue (blue arrow).