A Study On The Control And Cause Of The Withering Ofpinus Sylverstris Var. Mongolica In Yulin Sandy Area

The rate of infected Pines sylvestris Var. monglica achieved 10.7%, the rate of death was 6.6%(1.4-22.2%) through comprehensive investigating the distribution region of P. sylvestris Var. monglica in Yulin sandy area . the wilt mainly took place in the younger forest with 10 to 15 years old , the death mainly were apex and shoots , but the plants were green withered also.This paper investigated and analysised the site conditions, plant cover rate ,thickness of soil crust and moisture factor of dead P. sylvestris Var. monglica forest land . The authors preliminary considered that the adverse ecological factors caused physiological weackness of the trees , harm of ligonychus ununguis Jacohi had increased speed of death .This paper considered that Chaetomium globosum Kunze is had caused P. sylvestris Var. monglica death , through investigating the harmed degrees , dead characterisrics and symptom of infected plants of P. sylvestris Var. monglica , separating and culturing fungus from fresh infected plants , inoculation and second separating and culturing test .Chaetomium globosum Kunze fall under the class of Chaetomium , Chaetomiaceae,Sphaeriales .It could grow well at 18℃to 28℃, and optimum temperature was 25℃; the optimum pH was 6-8 .the sporule could bud well at 15℃to 28℃, and optimum temperature was 25℃.The peak period of infection was from the earlier of July to the later of August each year . The peak period of death of tree was middle of April to middle of May in the next year . It were possible to be released and transfered for sporule of the disease during the whole growing period . The frequency and quantity of rainfall directly influenced the transfer and amount of the sporule . Artificial inoculation showed that the time of infection for disease was mainly from middle of June to middle of August ,the period of the latency for disease is half month , the way to invade for the disease was through the injured part of tree , the infected part of a tree and dead twig were the places , where the pathogenic fungus lived inwinter .The control measures of Pinus sylvertris Var. mangolica of young growth disease in Yulin sandy area are put forward through chemical controls, the insecticide efficacy determination, field experiments , investigation of the measures for planting trees, and experiment of comprehensive control.The infectious lighter in Mancoze(50%WP, diluted, 400times) or in Thiophanate-methyl (70%WP, diluted, 400times) is controlled twice, the serious diease is controlled twice by the chemical insecticide on the basis of cleaning up the deadwood in the forest land. Mixed forest should be planted ,the density should be above 2m×3m to afforest . Afforestion of P. sylverstris Var. mongolica is unsuitable on lower and subsidiary dunes.