1. Shoot withering type: mainly occurs on shoots, and the initial symptoms are the same as ulcer type. However, it is difficult to form healing tissue after waterlogging and rot. When the affected part reaches more than 2/3 of the circumference of the young shoots, the young shoots bend, wilt and die from the affected part. The disease develops rapidly, and it takes only 4 ~ 5 days from symptoms to bud death. On rainy days, the diseased part will grow a layer of gray mold.
2. Ulcer type: it mainly harms cedar shoots. In the early stage, light brown round and nearly round irregular spots were produced at the base of the tender tip, and then gradually expanded into serious spots in the middle of the depression, and rotted into dark brown water stains in the early stage of the depression. After recovery, the original rotten epidermis cracked.
3. Twig withering mainly occurs on biennial twigs. The diseased spots mainly spread from dead twigs. At first, a circle of reddish-brown depressions was formed at the junction of dead branches and branchlets, and then obvious disease spots gradually formed, which did not crack, and a small amount of resin overflowed, and the surface layers of cortex and xylem were dark brown. One week after the lesion spread to the branchlet, the upper part of the branchlet died. The occurrence and prevalence of the disease are closely related to climatic conditions.
Prevention and cure method
(1) Cedar should be planted in a place with good drainage, ventilation and light transmission, and should not be planted too closely.
(2) dead branches should be cut and destroyed in time.
③ 65% zineb WP 500 times, 45% amobam aqueous solution 1000 times, 50% Bernoulli WP 1000 times, and 70% thiophanate-methyl WP 1500 times can be sprayed at the onset stage. The pathogen of Cedar Leaf Blight overwinters as mycelium (or ascomycete) in the diseased needle, and the ascomycete forms in March-April of the following year, and the ascomycete gradually matures in April-May. In rainy or humid conditions, the factor capsule disk expands and opens due to water absorption, revealing milky white capsule groups; The envelope is extruded from the envelope and further spread by air. The pathogen invaded from the stomata of cedar leaves, and it took about two months before obvious symptoms appeared. Because the meristem produced in the meristem holder has very poor germination ability and is not contagious, reinfection will not occur. However, because the radiation time of steamed stuffed bun is very long, reaching about 3 months, new infections may appear in Zhixia from spring. During the bag flight, if the precipitation is high and the humidity is high, it is beneficial to the invasion. Drought in forest land, thin soil, cedar diseases and insect pests and poor management may all lead to diseases.
Pollution prevention measures:
① Strengthen tending management to make cedar grow vigorously and enhance disease resistance.
(2) For small-area plantations, cedar nurseries and other places where conditions permit, diseased leaves should be removed before carpels fly away to reduce the source of infection.
(3) During the flight period after the ascomycetes emerge, spray 1: 2: 200 times of Bordeaux solution, 0.3-0.5 Baume sulfur mixed solution or 400-500 times of 25% warm carbendazim solution, or 8 times of 65% wettable powder for 2- 3 times, with an interval of 10-65438.