Application of the entomogenous fungus, Metarhizium anisopliae, for leafroller (Cnaphalocrocis medinalis) control and its effect on rice phyllosphere microbial diversity

Abstract

Microbial pesticides form critical components of integrated pest management (IPM) practices. Little, however, is known regarding the impacts of these organisms on the indigenous microbial community. We show that Metarhizium anisopliae strain CQMa421 was highly effective in controlling the rice leafroller, Cnaphalocrocis medinalis Guenee. In addition, M. anisopliae distribution and its effects on phyllosphere microbial diversity after application in field trials were investigated. Phylloplane specific distribution of the fungus was observed over time, with more rapid declines of M. anisopliae CFUs (colony-forming units) seen in the top leaf layer as compared to lower layers. Application of the fungus resulted in transient changes in the endogenous microbial diversity with variations seen in the bacterial observed species and Shannon index. Notable increases in both parameters were seen at 6-day post-application of M. anisopliae, although significant variation within sample replicates for bacteria and fungi were noted. Application of M. anisopliae increased the relative distribution of bacterial species implicated in plant growth promotion and organic pollutant degradation, e.g., Methylobacterium, Sphingobium, and Deinococcus. These data show minimal impact of M. anisopliae on endogenous microbial diversity with transient changes in bacterial abundance/diversity that may result in added benefits to crops.

Detection of the Entomopathogenic Fungus Beauveria bassiana in the Rhizosphere of Wound-Stressed Zea mays Plants

“…Given that a significant decline in all detectable Beauveria was observed by 30 DAI using PCR, this was not unexpected but may indicate that initial inocula levels did not have a lasting effect. A recent study by Hong et al (2017) also demonstrated that an application of M. anisopliae had a minimal impact on the endogenous microbial diversity of rice plants within the phyllosphere, with only transient changes in bacterial abundance/diversity that may have resulted in some small benefits to the plant. Thus multitrophic interactions are important to consider, in addition to any possible ecosystem impacts that may influence performance of a biocontrol agent applied to agroecosystems ( Ownley et al, 2010 ).…”

Members of chitin synthase family in Metarhizium acridum differentially affect fungal growth, stress tolerances, cell wall integrity and virulence

“…Conidial yield, stress tolerances, and virulence are very important parameters for entomopathogenic fungi with respect to biological control applications of the fungus [50–52]. Previous works in other filamentous fungi have shown that chitin synthesis impacts fungal conidiation.…”

Sustainable control of the rice pest, Nilaparvata lugens, using the entomopathogenic fungus Isaria javanica

“…Use of Metarhizium anisopliae (Metschn.) has been shown to be effective against the rice leafroller ( Cnaphalocrocis medinalis Güenée, Lepidoptera: Crambidae), without adversely affecting the rice phyllosphere microbial diversity, 26 and the effect of the insect microbiota in mediating susceptibility to infection is being increasingly examined 27,28 …”

“…25 Use of Metarhizium anisopliae (Metschn.) has been shown to be effective against the rice leafroller (Cnaphalocrocis medinalis Güenée, Lepidoptera: Crambidae), without adversely affecting the rice phyllosphere microbial diversity, 26 and the effect of the insect microbiota in mediating susceptibility to infection is being increasingly examined. 27,28 However, additional information is needed concerning the use of entomopathogenic fungi as components of sustainable pest control strategies for the control of N. lugens on rice.…”