Abstract:
Bananas constitute a major staple food crop for millions of people in developing
countries, providing energy as well as important vitamins and minerals. It’s
production in Kenya has been on the decline due to, among other factors, pests
and disease of which the banana weevil, Cosmopolites sordidus, is the most
important. The aim of this study was to screen ten isolates of the
entomopathogenic fungus Beauveria bassiana for pathogencity against C.sordidus.
Twenty weevils were inoculated with the fungus by dipping them into a fungal
suspension containing 1x108 conidia ml‐1 for 11 seconds. The suspension was then
drained out and pieces of banana corm introduced as food for the weevils. All the
ten isolates of B. bassiana tested were found to be pathogenic to adult banana
weevil causing mortalities of between 20‐50% by 40 days post exposure. ICIPE 273
was the most pathogenic isolate killing 50% of adults, followed by M313 at 36%
and M207 at 30%. Isolates KE300, M221, ICIPE 50, M573, M618, M470 and ICIPE
279 killed less than 30% of the weevils, ICIPE 279 was the least pathogenic isolate
to the adult C. sordidus killing 6% of the inoculated weevils. The dead weevils were
incubated in sterile moist filter papers in Petri dishes for two weeks and fungal
mycelia was observed on the surface of the weevils starting from intersegmental
junctions. Mortality caused by fungus was confirmed by microscopic examination.
Since isolate ICIPE 273 has reasonable pathogenicity to C. sordidus and
field/screenhouse studies are recommended to validate the findings.
