Study On The Identification Of A Novel Anthracnose And The Prevention And Control Technology Of White Rot Disease Of Acacia Melanoxylon In Guangdong And Guangxi Provinces

Acacia melanoxylon,which belongs to Mimosaceae,Acacia Mill,is native to Australia.The species is characterized by its short rotation period and superior wood properties.It has been introduced to China since the 1990 s and is currently being promoted in Fujian,Guangdong,Guangxi and other southern provinces.In recent years,the white rot disease(WRD)of A.melanoxylon which caused by Pseudolagarobasidium acaciicola has mainly caused the stems of A.melanoxylon or the whole plant to die.In this study,the study on the identification of a novel anthracnose and the prevention and control technology of white rot disease of A.melanoxylon The main innovative results obtained are as follows:1.A novel anthracnose of A.Melanoxylon was found.It mainly harms twigs,leading to the death of twigs.After the putative fungi was isolated and purified,it was identified as Colletotrichum spp based on both morphology and ITS sequence.2.The WRD symptom characteristics of A.melanoxylon were revealed.By investigating the main cultivation areas of A.melanoxylon in Guangdong and Guangxi,it was found that the disease mainly harms the stems of A.melanoxylon younger than 6years old and the branches of aged A.melanoxylon older than 6 years old.Brown lesions with different lengths formed on the epidermis of young trees’ stems,and gradually expand to the interior of the trunk,leading to deep depressions.Different clones of A.melanoxylon have different incidence rate,ranging from 5% to 20%.When the disease is severe,it would cause the death of young trees or the wilt of mature trees’ branches.The pathogen mainly invades from the wounds made by pruning during cultivation or typhoons.The course of this disease begins in April and ends in October,reaching the peak from June to September.3.The biological characteristics of P.acaciicola are proved.The suitable temperature range is 15 ℃-35 ℃,thereinto,the optimum temperature range is 20 ℃-30 ℃ and the optimum growth temperature is 30 ℃;the optimum growth medium is potato dextrose agar(PDA)and potato sucrose agar(PSA);the optimum p H range is6-8;P.acaciicola can grow normally both in full darkness and under different light conditions;glucose,sucrose,fructose,maltose,starch,mannitol and other carbon sources except lactose can be effectively used by P.acaciicola.4.The resistance level of the WRD of A.melanoxylon was tested.By inoculating the seedlings of five different half-year-old A.melanoxylon clones,it turned out that No.3,13,14,21,and 53 clones have different resistance to WRD of A.melanoxylon.The resistance of No.21 clone and No.53 clone were highest,No.3,No.13,No.53 followed,and No.14 was the worst.5.There were 5 kinds of fungicides had indoor fungi effects over 81.73% on the white rot disease of A.melanoxylon.Among all of the nine fungicides tested,there are eight ones had fungi effects on P.acaciicola.The antibacterial rates of 150 g / L Armure emulsifiable concentrate,15% triadimefon wettable powder and 70% mancozeb wettable powder were 100%,while 25% pyraclostrobin emulsifiable concentrate was95.19%,and 50% carbendazim wettable powder was 81.73%.6.Two kinds of fungicides were found to have therapeutic effects on the WRD of A.melanoxylon.150 g/L Armure emulsifiable concentrate,15% triadimefon wettable powder,70% mancozeb wettable powder and 25% pyraclostrobin emulsifiable concentrate,being proved to have the highest bacteriostatic rate,were sprayed on No.17 clone of half-year-old A.melanoxylon which had been inoculated by P.acaciicola seven days ago.After 39 DAI,it was found that the relative control effect of the above four fungicide was 51.56%,75.75%,27.27% and 9.09%,respectively.The incidence rate of control group inoculated and sprayed with sterile water was 100%,and the incidence rate of the control group inoculated with blank PDA cake was 0%.It showed that 15% triadimefon wettable powder and 150 g/L Armure emulsifiable concentrate have certain therapeutic effects WRD.7.Three kinds of fungicides were found to have protective effects on the WRD of A.melanoxylon seedlings.The same four fungicides as the above were sprayed on No.17 clone of half-year-old A.melanoxylon that has not been inoculated by P.acaciicola,and after 24 hours the pathogens are inoculated.After 39 DAI,the relative control effects of the four fungicides were 100%,100%,89.9% and 35.35% respectively.Comparing the results of the above two different application methods,it was found that the 15% triadimefon wettable powder had both a good therapeutic effect and a good protective effect against this disease.The 150 g/L Armure emulsifiable concentrate had a good protective effect but the therapeutic effect of it is ordinary.The 25%pyraclostrobin emulsifiable concentrate had a better protective effect.Both the treatment effect and protective effect of 70% mancozeb wettable powder were poor.