Study On The Developmental And Survival Dynamics Of Isaria Javanica And Metarhizim Anisopliae Surrounding The Host Plant

Isaria javanica and Metarhizium anisopliae are the most important entomopathogenic fungi used in biological control in agricultural and forest pest management.The survival and scatter of target fungi in field depends on many factors,such as,temperature,humidity,ultraviolet radiation in environment.Result from detection and monitor of released biological control fungi in field will help us to decide time,frequency and dose of application of fungi needed to effectively control different insect pests.The developmental and survival dynamics of I.javanica and M.anisopliae on three different soils(field soil,sand and red soil)were observed under microscope and analyzed by the method of petri dish culture.At the same time,the developmental and survival dynamics of I.javanica and M.anisopliae surrounding three different host plants,including on plant foliage and in soil surrounding the root of Chinese kale,cucumber and tomato,were also evaluated after the fungus is released.The spore germination rate of I.javanica and M.anisopliae on the metabolite of three plants,including joice from foliage and root of Chinese kale,cucumber and tomato,were tested in order to know the effect of plant metabolite on fungi survived in field.All the experiments were performed as follows:(1)The developmental and survival dynamics of I.javanica and M.anisopliae in soil.After releasing the spore of target fungi into three different soils,the time of I.javanica and M.anisopliae survived in soil surrounding plant root,in the areas with a radius of 2 cm from the point of inoculation,were up to 80 days.The number of two fungi survived in soil surrounding plant root decreased differently in different soils with time goes on,the number of M.anisopliae survived was higher than that of I.javanica at the same time tested.(2)The developmental and survival dynamics of I.javanica and M.anisopliae in the rhizosphere soil.The developmental and survival dynamics of I.javanica and M.anisopliae in soil were detected with no relation to the direction of water flow,the survival of I.javanica and M.anisopliae in soil,at the place with a radius of 1 cm from the point of inoculation,was closely related to the direction of water flow.The time and number of I.javanica and M.anisopliae survived in the rhizosphere soil in field were related to season and host plants.In autumn and winter,the longest time of I.javanica and M.anisopliae survived were up to 60 days in rhizosphere soil surrounding plant with a radius of 2 cm from the point of inoculation,the plant involving Chinese kale,cucumber and tomato in the field.In summer,the time of M.anisopliae survived in the rhizosphere soil surrounding cucumber and tomato roots were shortest,with value of 20 days.In soil at the places with a radius of 4 cm from the point of inoculation,the survived I.javanica was detected in soil surrounding three plant roots at the time from No.30 to 60 day after the fungi is released in autumn and winter,the same as M.anisopliae detected at the time from No.20 to 60 day.As to the places with radius of 6 cm,the survived I.javanica was detected in soil surrounding Chinese kale and cucumber roots at the time of No.60 day after released in autumn and winter,similar to the survived M.anisopliae detected in soil surrounding Chinese kale and tomato roots.(3)The developmental and survival dynamics of I.javanica and M.anisopliae on plant foliage.Only spore of I.javanica was observed under microscope on foliage of Chinese kale in 4 days after it is sprayed on the surface of plant leaves.Spore of I.javanica was also observed on foliage of cucumber and tomato in 2 days,however,much mycelium and sporospora were detected on foliage at 3-4 d post fungi released.Only spore of M.anisopliae was observed on foliage of Chinese kale,cucumber and tomato in 4 days after target fungi is sprayed on the surface of plant leaves.The time of I.javanica and M.anisopliae survived on foliage in field were related to season and host plants.In spring,the longest time of I.javanica and M.anisopliae survived on foliage were up to 15 days,the plant foliage involving Chinese kale,cucumber and tomato in the field.In summer,the time of M.anisopliae survived was only 7 days on the foliage of cucumber.The number of I.javanica survived on plant foliage was higher than that of M.anisopliae survived on the same foliage.The number of I.javanica and M.anisopliae survived on foliage in field were related to season and host plants.(4)Influence of plant metabolites on fungal spore germination.Isaria javanica spores can germinate when cultured in leaf and root juice extracted from three different plants(Chinese kale,cucumber and tomato),and M.anisopliae spores could germinate in leaf and root juice extracted from Chinese kale and cucumber.The germination rate of I.javanica spores in leaf and root juice was higher than that of M.anisopliae spores in the same juice,the germination rate of I.javanica spores increased in sterilized leaf and root juice,however,the germination rate of M.anisopliae spores decreased in sterilized leaf juice and in root juice from cucumber and tomato.The germination rate of M.anisopliae spores increased in root juice from Chinese kale.