The Occurrence Regularity And Control Experiment Of Tar Spot Of Ficus Religiosa

Ficus religiosa is an important ornamental tree in gardens.According to the investigation,tar spot of Ficus religiosa is an important disease.In this paper,biological characteristics of the pathogen,tar spot of Ficus religiosa,the occurrence rule of the disease in the forest,indoor screening of fungicides for controlling,the chemical control experiment in the field and the risk analysis of the disease were carried out.The main research results are as follows:1.Test of biological characteristics of the pathogen.Germination temperature range of pathogenic ascospores were 10 ?-38 ? and the optimal germination temperature was 25 ?.Over 53 ?in 20 min ascospore will die.Germination rate of ascospores could germinate on the condition of relative humidity above 90%and the highest germination rate(66%)was on the condition of relative humidity above 100%.Ascospores could germinate in the range of pH 5-10 and the highest germination rate(70.5%)of ascospores was on the condition of that pH value was 7.Ascospores do not germinate on the condition of that pH values was below 5 or above 10.Sodium nitrate from common nitrogen sources could stimulate the germination of the ascospores.2.Occurrence regularity of tar spot of Ficus religiosa in forest.Tar spot of Ficus religiosa occurs throughout the year.Growth rate of disease index of the disease kept high from April to August,the highest of growth rate of disease index occurred in June,growth rate of disease index increased slowly from September to November,the highest disease index was accumulated in December,and there was no change on disease index from November to February.The growth rate of disease index of the disease was significantly positive related to average rainfall and relative humidity and was obviously related to temperature.3.Dynamic state of amount of ascospore in forest.Ascospore released to peak in June and November(4.50×105/m2 and 4.78×105/m2 in a square meter).There was obvious difference on amount of ascospore released in different month,ascospore amount was the lowest in January(1.75×105 in a square meter),and ascospore amount was enough for infection in forest.4.Indoor screening of fungicides for controlling and chemical control experiment in field.Virulence test against the pathogen showed that bordeaux liquor,mancozeb,imidazepam,carbendazim and methyl sulforaphane had strong inhibitory activities on ascospore germination.The EC50 values of 80%mancozeb wettable powder and equivalent bordeaux liquid were the lowest,0.007 mg/L and 0.0075 mg/L,respectively.Among the control experiment in field,bordeaux liquid,taking turns applying mancozeb and imidazine had better control effects,which reached 50.25%and 47.11%,respectively.5.Tar spot of Ficus religiosa risk assessment.After the risk of tar spot of Phyllachora repens was assessed,the risk coefficient of tar spot of Ficus religiosa was 2.024,which belonged to a highly dangerous pest.Based on that distribution of the pathogen is very limited now,Phyllachora repens should be listed as a quarantine pest.