bark rot of Korean pine

Pine bark rot disease is also called drooping branch disease, soft branch disease, dead branch disease, withered shoot disease, is a branch ulcer disease, mainly harmful to pine species.

Symptoms: The disease harms the bark of the branches of young Korean pine trees, and can also occur at the base of the trunk when it is serious, causing canker disease. The pine needles above the infected parts turned yellow-green to gray-green, and gradually turned brown to reddish brown. The injured branches shrink and wrinkle due to water loss, and the needle drop marks are slightly enlarged. When the lateral branches are diseased, the lateral branches will droop downward. Branchlet base disease, it shows withered branches symptoms. When the trunk comes on, the diseased part flows fat, the ulcer occurs and the skin is rotten, the diseased skin gradually shrinks and sinks, and the fat flow intensifies. In April, cracks occur in the cortex of the onset part, from which yellow-brown discs are produced, which are asexual discs of pathogenic fungi. Asexual discs form clusters of 1-several, gradually grow up, become darker in color, and expand into disk-like clusters in case of rain. After drying, it shrinks and turns black, and its edges curl from both sides or 3 directions to the center.

Pathogen: Cenangium ferruginosurn Fr. ex Fr., It belongs to Ascomycetes, Discomycetes and Mollicutes.

Pathogenesis rule: The disease harms young tree branches more than 4 years. The pathogen overwinters as mycelium in the infected plant bark, pine needle wilt appears in the spring of the next year, and asci are produced from the bark plant in the first and middle of March and April. The ascocarp matures from late May to late June and releases spores. Ascospores can last about 3 months. Spores spread by wind and rain, germinate in wet conditions and invade the plant skin through wounds, and then show symptoms after overwintering. Pathogenic bacteria often live on the lower branches of trees, actively decompose dead skin on dead branches, promote natural pruning, so it is also called pruning bacteria. When pine trees grow weakly due to drought, waterlogging, freezing, insects, over-dense planting or poor soil, it can infect the weak trunk bark and cause rotten skin symptoms. In addition, when young trees grow weak due to aphids and scale damage or snow pressure, the disease spreads rapidly and causes huge losses.

Control: ① suitable for trees, timely tending, reasonable pruning, removal of dead trees and sick trees.② Control aphids, pine scale and other pests. 3. It can be sprayed dry with 1:1:100 Bordeaux mixture or 2-degree stone sulfur mixture, or it can be treated with pine tar or 0.2% mercuric diesel oil.