Liquid Phase Media for Mass Production of Metarhizium anisopliae against Sorghum Chafer, Pachnoda interrupta, using Rice as Solid Substrate

Abstract

Microbial biological pest control agents such as entomopathogenic fungi (EPF) can
be an effective alternative for the control of sorghum chafer, Pachnoda interrupta,
an important pest in Ethiopia. Production of inoculums of high quality with
reasonable quantity on mass production substrates is important for its use as
mycoinsecticides. Three liquid phase media viz. sucrose /waste brewer’s yeast
(SWBY), molasses/yeast extract (MYE) and lennoux broth base (LB) were evaluated
for effects on mass production characteristics of three M. anisopliae isolates viz.
PPRC51, PPRC2 and IC69 using rice as a solid substrate in the diphasic mass
production technique. Effects of liquid media on shelf-life and virulence of the
isolates against P interrupta was also evaluated. Weight of spores/kg of rice
substrate, number of spores/g of spore powder and viability of spores varied
significantly across the three isolates (P<0.0001). There was no significant difference
among liquid phase media and their interactions with isolates (P > 0.05). The highest
weight of spores (119.72g/kg) was obtained from IC69 mass produced by using
MYE as a liquid phase medium. PPRC2 produced the highest number of spores
(4.57x1010 spores/g) when using LB as liquid phase medium. Using MYE as liquid
phase medium, the virulence of the three isolates of M. anisopliae did not vary
significantly. Using either of the liquid media does not significantly affect all the
quality variables for mass production, virulence and shelf life of the isolates selected
for control of P. interrupta. Therefore any of the liquid phase media can be used for
mass production of the selected isolates on rice without significantly affecting
virulence and shelf life.