Abstract

The grasshopper, Zonocerus variegatus, is a crop pest in Africa that causes significant damage to crops and forest tree seedlings. The application of synthetic chemicals as management technique in the control of Z. variegatus has deleterious effects on the ecosystem. Therefore, it becomes pivotal to explore other better and safer strategy in the management of this pest. To this end, this study evaluated some isolates of entomopathogenic fungi, Beauveria bassiana, as an alternative in controlling Z. variegatus under laboratory conditions. Synthetic insecticide DDVP (2, 3-dichlorovinyl dimethyl phosphate) and sterile distilled water were used as positive and negative controls, respectively. Contact toxicity and food bioassay methods were employed in the experiments. Mortality counts of the insects were recorded daily for 5 days. The result of the contact application showed that isolate Bb 362 caused significantly higher mortalities of 63% and 90% at 1- and 5-days post application, respectively. Isolates Bb 115 and Bb 11 caused 40% and 55% insect mortalities, respectively, at 5 days post-application. Application of DDVP (2,3-dichlorovinyl dimethyl phosphate) caused 100% insect mortality within 24 hours post application, while food treated with fungal suspensions recorded low insect mortalities after 5 days post application. The study conclusively established that contact toxicity of Beauveria bassiana isolate Bb 362 showed promising potential in Z. variegatus management and can be used as an effective biocontrol agent.

Key Word: Entomopathogenic fungi, Beauveria bassiana, Zonocerus variegatus, Mortality, Biocontrol agent