Evaluation of Ethiopian Isolates of Entomogenous Fungi as Potential Biological Control Agent of the Desert Locust, Schistocerca Gregaria.
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Date
1998-05
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Addis Ababa University
Abstract
Ten native fungal isolates were collected from the different regions of Ethiopia. Eight of the
isolates were identified at International Institute of Tropical Agriculture, UTA, Benin. Five of
the isolates were identified as Beallveria, two were Paecilomyces and one belonged to
Metarhizilllll species. Eight of the tested fungal isolates showed pathogenecity to fifth instar
Schistocerca gregaria. The Beallveria spp. isolate FF and MetarhiziulII spp. EE were more
virulent compared to the rest. Thus two isolates were further assayed in peanut (Arachis
hypogaea) and noug (GlIizotia abyssinica) oil formulations, and compared with a known
entomopathogen, M anisopliae ICIPE 30. The results indicated that there were strong doseresponse
patterns. Peanut oil formulation enhanced infectivity of both FF and EE. Infectivity
of EE was significantly (P<0.05) reduced in noug oil formulation. Comparison of virulence
revealed that isolates FF and EE were more pathogenic than ICIPE 30. FF in peanut oil
formulation had the lowest LCso value of2.02xlOs conidia/ml followed by EE, 2.93x10s and
ICIPE 30 with 4.98x10s conidia/m!. The highest mortality was achieved by FF at Ixl08
conidia/ml, resulting in 50% and 100% mOliality in 4.2 days and seven days, respectively.
The median lethal time taken to fOUlih, fifth and adult FF treated insects were 3.47, 4.14 and
4.83 days; respectively that indicated fourth instars are more susceptible. Insects killed as a
result of FF infection developed red pigmentation and produced white powdery mass of
spores on the external surface. The Metarhizilllll isolates EE and ICIPE 30 produced green
sporulation on the integument when the cadavers were kept at high humidity. FF and EE grew
at a temperature range of 24°C and 37°C, with peaks at 24°C and 28°C for FF and 28°C for
EE. Malt extract agar favoured growth and sporulation of FF, whereas EE grew and
sporulated faster on sabouraud dextrose agar. Germination of both isolates was significantly
(P<0.05) high in peanut oil formulation than in noug oi!.
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Biology