A Detailed Guide to Integrated Control Methods for Apple Tree Valsa Canker

Once Valsa canker appears during the cultivation of apple trees, it has a major impact on both the yield and quality of the apples, so growers must understand the symptoms and integrated control methods of apple tree Valsa canker to reduce the damage to a minimum.

1. Symptoms of apple Valsa canker

In the early stages of apple tree Valsa canker, the bark layer at the affected site turns slightly brown, and the boundary tissue of the affected area is clearly defined. As the lesion gradually expands, the affected area swells and softens; pressing it with a finger leaves a depression, and a yellowish-brown liquid oozes out. Later, the scar at the affected site dries, shrinks and becomes dark brown. Many small brown granular substances appear on the affected bark. When it rains or the weather is humid, an orange-yellow filamentous curled material often exudes from these small black spots. In severe cases of apple tree Valsa canker, the leaves on the branches and trunk turn yellow and may even wither and die.

The pathogen that causes apple tree Valsa canker is a weak parasitic fungus. Its mycelium, conidial pycnidia and perithecia overwinter in the bark of apple trees or in old disease scars.

Infection and disease onset can occur in all three seasons of spring, summer and autumn, but the peak periods of disease onset are May and September each year. The pathogen spores continue to spread with wind and rain. When they encounter wounded apple trees and suitable environmental conditions, they trigger Valsa canker. Old fruit trees and weak-growing apple trees are especially prone to the disease.

2. Integrated control methods for apple tree Valsa canker

1. Strengthen integrated management and enhance tree vigor. Take a healthy, robust tree as the foundation for disease prevention and the elimination of pathogenic bacteria as the guarantee, and carry out integrated control. First, emphasize applying organic fertilizer in autumn, increase the application of phosphorus and potassium fertilizers, spray medium and trace element fertilizers and various nutrients, grow grass between the rows, build up soil fertility and promote root development. Second, strengthen measures to protect leaves and roots, and promptly control various pests and diseases and freeze injury. Third, expand the cultivation of virus-free, disease-resistant varieties, determine a reasonable planting density and reasonable tree shape, carry out reasonable pruning and ensure ventilation and light penetration. Fourth, maintain a reasonable crop load to prevent tree decline and promote robust tree growth.

2. Promptly remove the pathogen. After fruit harvest, promptly clean the orchard, sweep up fallen leaves, remove dead and diseased branches and pest-damaged branches in the orchard, scrape off coarse old cracked bark, and promptly collect the rotten diseased bark and debris scraped from diseased trees and branches and destroy them in a centralized manner. Reduce the base number of pathogens to lay a good foundation for Valsa canker control.

3. Carry out regular inspections and timely treatment. Valsa canker requires regular inspection and treatment as soon as it is found. For small lesions, carry out scoring treatment; for large lesions, carry out scraping treatment, and apply medicine promptly. Wounds that have been treated by application must be rechecked and treated again. Commonly used application agents: Fulanke, Guokangbao, tebuconazole, flusilazole, propiconazole, Letu No. 2, lime sulfur mixture, etc.

4. Bridge grafting. When the lesion treated by scraping for Valsa canker is relatively large, it directly affects the transport of nutrients. To prevent tree decline, bridge grafting should be carried out on the tree to make up for the insufficient nutrient transport and protect the tree.