Control Methods for Strawberry Leather Rot, a Must-Read for Growers

In recent years, along with the optimization and adjustment of the planting structure, the strawberry cultivation area in Laizhou City has expanded rapidly. Due to continuous cropping, strawberry diseases have shown a worsening trend, especially the emergence of strawberry leather rot, which has a great impact on the yield and quality of strawberries, and in severe plots it even causes total crop loss. The symptoms and control methods of strawberry leather rot are described as follows:

I. Symptoms. Strawberry leather rot mainly occurs on the fruit and roots, and can also occur on the runners.

1. Roots: The roots are affected first. When a diseased root is cut open, it can be seen turning black from the outside inward, with a leathery rot appearance. Field observation: In the early stage, plants show no symptoms; in the middle stage, they only show poorer growth and are slightly stunted; by the flowering and fruiting stage, the aboveground parts appear dehydrated, gradually wilt, and eventually the whole plant dies.

2. Fruit: Affected fruit shows light brown water-soaked spots, which can rapidly spread to the whole fruit. The diseased area fades in color and loses its gloss, and when lightly pinched by hand it feels leathery and hard. When humidity is high, white mycelium grows on the fruit surface.

3. Seedlings: The disease can also occur during seedling propagation. The main symptoms are the runners drying out and wilting, and finally drying to death.

II. Pathogen. The pathogen causing strawberry leather rot is Phytophthora cactorum, also known as apple Phytophthora, belonging to the order Peronosporales in the subdivision Mastigomycotina. The hyphae are colorless, branched, and non-septate. Sporangia are terminal, nearly spherical or oval, with relatively prominent papillae. Detached sporangia have a short stalk. The temperature range for hyphal growth is 10-30°C, and the optimum temperature is 25°C.

III. Conditions for Disease Occurrence

1. Soil and seedlings. This disease is a soil-borne fungal disease. Planting disease-free seedlings in disease-free fields generally does not lead to disease occurrence. Therefore, whether a source of inoculum exists in the soil and whether strawberry propagation material carries the pathogen are the prerequisites for whether this disease occurs.

2. Climatic conditions. This disease is a moderate-temperature-type disease. Under conditions of rising temperatures and relatively high humidity in mid-to-late May, it is favorable for the occurrence and spread of this disease.

3. Cultivation factors. Continuous cropping or repeated cropping in diseased fields aggravates the disease, and plots with poor drainage and night-damp soil are prone to the disease.

IV. Control Methods: (1) Establish disease-free seedling propagation bases and implement unified seedling supply. (2) Level the land, connect ditches, and prevent water accumulation. Irrigation should be carried out from 10 a.m. to 2 p.m., striving to let the water drain by evening. (3) Once disease occurs during the growth period, carry out chemical control promptly. Root drenching can be done with 64% Sandofan, yellow humate, etc., and foliar spraying can be done with 72.2% Previcur at 600 times dilution, 72% Curzate at 600 times dilution, etc., all of which can achieve relatively good control effects.