Preliminary Study On The Control Of Cotinus Coggygria Verticillium Wilt In Fragrant Hill

This paper carried on some experiments including clarifying the relationship between occurrence degree of Verticillium wilt and environment factors,screening selective medium and screening method for Verticillium.dahliae microsclerotia,detecting and evaluating the host resistance of common tree species in Frangrant Hill,and preliminary methods for disease control.To provide basic data for further explaining the law of the disease occurrence and its control.1 The relations between occurrence degree of Verticillium wilt and stand factors of Cotinus coggygria in Frangrant Hill were investigated.The results indicated that these factors including slope, soil moisture,soil thickness,soil humus layer thickness had a certain impact on the occurrence of diseases,and Verticillium wilt disease index had close relationship with soil moisture content,with rising the extent of soil moisture content,disease index was also increasing.2 Five selective media,including modified soil extract agar(MSEA),cotton No.1,Christen media, Yang Jiarong media and alcohol agar media,for isolating microsclerotia of V.dahliae from artificially infested soil were selected.Cotton No.1 and Yang Jiarong media were effective media for isolating microsclerotia of V.dahliae.The germination rates of sclerotia were relatively high and sclerotia were easy to indentify.Soil dilution,wet-seiving and sucrose-floatation methods were compared in recovery rate and results stability,separating artificially infected soil.The result showed that the stability of sucrose-floatation method was the best and its recovery rate were about 45.4%.3 The inhibitory rates of eight varieties of fungicides to the pathogen of verticillium wilt of C. coggygria were determined by measuring mycelium growth.Four fungicides,showing the best antifungal effect,were selected to determine the effect on potted transplants.The effect of the four fungicides in controlling the disease was determined using potted 2-year-old smoke tree seedlings, inoculated with V.dahliae for 10 d.Based on the test results,Weijunjing,carbendazim 50%wettable powder(WP) were selected for field trials.The field trial results showed that in 2007 the best relative effect of Weijunjing(300 times diluted) in controlling wilt disease combined with soil disinfection on verticillium wilt of smoke tree was 66.2%in plot 1,26.4%in plot 2,22.4%in plot 3 and that of carbendazim 50%WP(400 times diluted) combined with soil disinfection was 48.9%in plot 1,31.8% in plot 2,61.8%in plot 3.In 2008,the relative effect of Weijunjing(300 times diluted) and carbendazim 50%WP(400 times diluted) was 49.6%and 45.4%in plot 2 respectively.4 The relationship between the occurrence degree of Verticillium wilt of potted seedlings of Cotinus coggygria and watering regium of potted seedlings was explored.The result showed that the HL group,which was heavy watering initially and lightly watered 15 days after inoculation,had the heaviest symptoms and its percentage of wilted leaves was 83%.While the LL group,which were lightly watered fore-and-aft inoculation showed the lightest symptoms,its percentage of wilted leaves was 41.45%.5 Inoculation was conducted to test the resistance to V.dahliae with potted seedlings of Cotinus coggygria,Robinia pseudoacacia,Koelreuteria paniculata,Prunus davidiana,Fraxinus chinensis, Syringa oblata,Pinus tabulaeformis.The results showed that C.coggygria and K.paniculata were susceptible to the V.dahliae and the fungus can be isolated from infected branches.And the others were resistant.The C.coggygria was the more susceptible species,and the incidence rate was up to 70%and the disease index was 52.5,26 days after inoculation.The K.paniculata was less susceptible species, and the incidence rate was 40%,the disease index was 22.5,26 days after inoculation.