The Development of Die-back of Pines by Sphaeropsis sapinea

The die-back of pines caused by Sphaerpsis sapinea (Fr.) Dyko & Button widely occurred in Jiangsu Province in recent years. Pycnidia of the causal fungus developed on infected needles, sheathes and scaly-leaves. Conidia are dispersed by rain. The pathogen of die-back of pine can't dissminated by seeds. The infectious stages of pine shoots coincided with the conidia-releasing stages respectively. The tender shoots are highly susceptible when their lengths reach to about one-third of the total length. The pathogen invade the shoot by direct penetration through the epidermis. Mature pine stands may become more susceptible, but young stands surrounded by severely diseased mature pine stands is also infected severely. Pine stands on poor sites are seriously infected. Pinus massoniana is the most resistant species of the genus. The other species in order of susceptibility are Pinus riglda, P. bariksiana, P. taeda, P. elliottii, P. thunbergii, and P. yunnanensis.