Study On Pathogen And Chemical Control Of Gummosis Of Zanthoxylum Bungeanum

Prickly ash（Zanthoxylum bungeanum）,planted for a long time in China,first recorded in The Book of Songs,is a small deciduous tree of ZanthoxylumL.of Rutaceae,and is a Chinese peculiar spice with diet and medicine value.In recent years,with the graduate expansion of its dimensions in industrialization of prickly ash,it is often affected by various diseases and insects during the cultivation,such as root rot,leaf rust disease and canker disease and aphids.Where in the prickly ash plantation of Hanyuan County,Ya’an City,Sichuan Province,a serious trunk gummosis disease was found,which can cause the death of prickly ash and seriously hinder the healthy development of industry.In this study,the pathogen of Gummosis of Zanthoxylum bungeanum was isolated and identified.Using the mycelial growth rate method,fungicides were screened out which have a good antibacterial effect preliminarily.Then complete the field test to further verify the control effect of fungicides.The main results are as follows:1、The pathogen was isolated and identified from the infect trees of Z.bungeanum.Six fungi were isolated and the pathogenicity was detected.It was found that strains GZ4 and GZ6 conformed to Koch’s law and identified as Fusarium tricinctum and Phomopsis perniciosa by the analysis of morphology,the r DNA-ITS gene sequence.The spores of GZ4strain are curved,pointed end is sharp,spindle or sickle-shaped,7.82-10.45μm×1.56-2.45μm,with multiple divisions.There are two kinds of spore forms in strain GZ6.Typeαconidia are colorless,oval or spindle,7.82-10.45μm×1.56-2.45μm.Typeβconidia are colorless,linear to hooked,17.65-34.88μm×0.87-1.14μm.The two pathogens fungi were identified as F.tricinctum and P.perniciosa by molecular biology identification and phylogenetic tree construction.2、The biological activities of ten different fungicides comprising of single-does and mixtures were tested against the F.tricinctum and P.perniciosa by toxic media method in lab.The results showed that the inhibition rate of mycelial growth was significantly different.250g/L Pyraclostrobin,325g/L difenoconazole·azoxystrobin,22.5%picoxystrobin had a stronger inhibitory effect on F.tricinctum,their EC₅₀ value were 0.4884μg/mL,0.7274μg/mL,0.3344μg/mL.The virulence of 500g/L Iprodione and 50%Boscalid were the weakest and the EC₅₀value were 115.1907μg/mL,124.5236μg/mL.250g/L pyraclostrobin,325g/L difenoconazole·azoxystrobin,10%difenoconazole had a stronger inhibitory effect on P.perniciosa,their EC₅₀ value were 0.8109μg/mL,0.7579μg/mL,0.9192μg/mL.The virulence of 50%Boscalid and 70%Propineb were the weakest and the EC₅₀value were115.1907μg/mL,124.5236μg/mL.3、In the field experiment,the conventional spraying method was used to spray four kinds of fungicides on the flow gum parts and the trunk of the disease plant.It is significantly different that the result four fungicides in the field efficacy test,and the best performer was22.5%picoxystrobin（2000-fold dilution）which show 69.07%control effect,followed by10%difenoconazole,250g/L pyraclostrobin,325g/L difenoconazole·azoxystrobin,their control effect were 32.42%,30.04%,14.34%.The results showed that 22.5%picoxystrobin is the most efficient fungicide to control this disease than others.