Analysis on Urediniospore Spreading Law of Melampsora laricipopulina in Guanzhong Area of Shaanxi Province

The spreading rule of urediniospores of Melampsora laricipopulina, which is the pathogen of Populus cathayana leaf rust disease, in Guanzhong Region of Shaanxi Province was primarily studied by means of urediniospores grab technique and Gray Theory. The results showed that urediniospores were start to be spread around August and to be ended in early November each year, the maximum spread in the mountainous and plain areas was in midSeptember and midOctober respectively. The mathematical model of the urediniospore spreading rule was Xt=81.08×e-0.49t in STC plot. This study revealed that Populus cathayana leaf rust disease caused by Melampsora laricipopulina occurred in the west of Guanzhong, and then spread from west to east, from low latitude to high latitude, from high altitude to low altitude and from the mountainous area to the plain area.