Leaf rust of spruce

Spruce leaf rust is distributed in Sichuan, Yunnan, Gansu, Qinghai, Taiwan and other places. The disease harms Lijiang spruce, scaly spruce, coarse spruce, oil wheat spruce, Linzhi spruce, snow spruce and Siberian spruce.

Symptoms: the young buds are susceptible, the needles on the newly growing shoots turn yellow or orange, short and thick, and the diseased leaves produce orange cushion-like winter spores or blister-like spores, the diseased buds look like a yellow flower, and soon the diseased leaves turn black and die. The susceptible 2-year-old leaves turn yellow locally, producing blister-shaped spores, or orange-yellow cushion-shaped teliospores.

Pathogen: the pathogen is golden rust fungus (Chrysomyxaspp.), which belongs to basidiomycetes subphylum, winter sporomycetes and rust order.

Morbidity rule: the life history of the disease varies with different pathogens. Golden rust of trumpet tea, rhododendron gold rust, amber gold rust and sparse gold rust belong to long cycle life cycle, while malformed gold rust and Verkin rust belong to short cycle life cycle, only winter spore stage. Spruce leaf rust caused by gold rust fungus spruce. At the turn of spring and summer, rust spores are produced on the needles, which are broken and spread to the leaves of rhododendron by wind, germinate or invade from stomata, and produce teliospores on the back of the leaves. Winter spores do not overwinter. in overcast and rainy weather, they can germinate and produce basidium and basidiospore. Basidiospores spread to the tender shoots of spruce by airflow, germinated and invaded, and overwintered in the host buds. In the second year, the sporangium and sporidium were produced on the needles. Spruce leaf rust has only the winter spore stage, and the pathogen overwinters with hyphae in the bud. In the second year, all the needles that sprouted from the disease were susceptible. Teliospores germinate to produce basidiospores and basidiospores in overcast and rainy weather. Basidiospores overwinter in the overwintering buds of spruce.

Control: ① reduces the source of infection: eradicate the intermediate hosts around spruce, such as rhododendron, trumpet, tea and so on. Cut off the disease buds and destroy them centrally. ② chemical control: in late spring and early summer, better efficacy was achieved by spraying Fenjining, Hydrin, sulfur gel suspension, 75% chlorothalonil wettable powder and so on.