Journal of Applied Biosciences (J. Appl. Biosci.) [ISSN 1997 - 5902]
Volume 47: 3221 - 3229. Published November 29, 2011.
The effects of spore concentrations of entomogenous fungi on larval mortality and development of the maize stem borer Eldana saccharina Walker (Lepidoptera: Pyralidae).
Baidoo P. K. and Ackuaku S. K.
Department of Theoretical and Applied Biology, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana.
Corresponding Author: Email: pkbaidoo2002@yahoo.com
ABSTRACT
Objective: The use of chemical insecticides to control insect pests has detrimental effects on the environment. There is therefore the need to look for alternative means to manage pests which can achieve substantial pest control with no negative effects on the environment. This study was conducted to determine the effects of spore concentrations of entomogenous fungi on the mortality of Eldana saccharina.
Methodology and Results: Entomogenous fungi were isolated from dead E. saccharina larvae and screened for pathogenicity. Different spore concentrations of the fungal species were tested against 2nd instar E. saccharina. Median lethal concentration (LC50) for each fungus was determined using probit transformed dose-response graphs. Fungal species identified were Aspergillus flavus, Verticillium albo-atrum, Trichothecium spp., Fusariunm oxysporum and Alternaria brassicicola. A. flavus had the least LC50 whilst F oxysporum recorded the largest LC50. Median lethal concentration of A. brassicicola was not determined because the pathogenicity test recorded only 22.5 % mortality.
Conclusions and applications of findings: The effectiveness in the use of a fungus as a biological control agent for the control of insect pest depends on both the pathogenicity of the fungus and the number of infective spores that the insect is exposed to. The use of entomogenous fungi is a viable alternative in the control of insect pests. They have an added advantage because they kill only the target pests and are therefore environmentally friendly. The study indicated that mortality is influenced by dosage and therefore higher doses produced higher mortalities. These fungi occur naturally and can therefore be conserved and used as a component in an integrated approach to the management of maize stem borers.
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