What are the control methods for apple rust?

China is a major apple-growing country, but the larger the planting area, the more diseases there are. Apple rust is an extremely common disease in apple orchards. It is also known as red star disease and is a typical heteroecious rust disease. The outbreak of this disease affects the growth and yield of apples and brings huge losses to fruit growers. Let's take a look at its control methods below.

1. Symptoms

Rust mainly affects apple leaves, and also harms the young parts of the plant, such as young twigs, young fruit, and fruit stalks. When the leaves are affected, small orange-red spots appear on the upper surface of the leaves and slowly expand until they form round orange-yellow lesions with red edges. In severe cases, multiple or a dozen lesions appear on the leaves, densely covered with yellow granular spots, and a cluster of yellow fuzz grows on the underside of the leaves. When young fruit is affected, round lesions appear on the fruit surface, initially orange-yellow, gradually turning yellow-brown, and finally tubular rust spore structures appear around the lesions, causing the affected fruit to fail to grow normally and mostly become deformed fruit.

2. Conditions for onset

Rainy and windy weather with suitable temperatures are the external conditions for apple rust. Its outbreak is directly proportional to precipitation. The greater the soil moisture and air humidity, the more favorable it is for the spread of this disease. Therefore, when planting, attention should be paid to drainage and waterlogging prevention measures during the rainy season, and ventilation should also be strengthened to reduce air humidity.

3. Pattern of occurrence

The pathogen of apple rust is Gymnosporangium yamadae, also known as Gymnosporangium asiaticum, a fungus of the subphylum Basidiomycotina, and it is a heteroecious parasitic fungus. The pathogen overwinters as mycelium on the branches and leaves of Chinese juniper, and in the second year forms microspores on Chinese juniper, which are spread by wind to apple plants for infection. Its transmission distance can reach up to 50 kilometers.

4. Control methods

First, eliminate the alternate host by cutting down all Chinese juniper, dragon juniper, and other such trees within 5,000 meters of the orchard. If they cannot be cut down in time, spray them with fungicide to eliminate the overwintering source of inoculum. During pruning, cut off the galls on Chinese juniper and burn them in a centralized manner. When establishing an apple orchard, pay attention to planting density and do a good job of pruning so that the plants have good ventilation and light transmission. Take drainage measures during the rainy season to reduce air humidity. In autumn and winter, clean the orchard in time, and burn or deeply bury the remaining branches and fallen leaves in a centralized manner to reduce the pathogen.

The above is an introduction to the control methods for apple rust. I hope it can help you. If you want to learn more related knowledge, please follow us.