| Abstract: | The effects of six fungal isolates; DLCO-AA-5, DLCO-AA-14, IITA 18, IMI 330189, DLCOAA-83 and DLCO-AA-109 were evaluated in the laboratory for their pathogenicity to adults,
5 and 6 larval instars of both the greater wax moth (Galleria mellonella) and lesser wax
moth ( Achroia grisella). Conidial dilutions were prepared in 0.5% Tween 80. The adults of
both species were treated by spraying while dipping the larvae in varied fungal concentrations
ranging from 2xl04 to 2xl07 conidia/ml. Assessments of larval infection of both the greater
. and lesser wax moth was made daily for 14 days before entering the pupal stage after
treatment. Mortality assessment for the lesser wax moth adults was made daily for 8 days post
treatment. Adults of both the greater and lesser wax moths were found to be susceptible to all
fungal isolates and concentrations, ranging from 2xl04 to 2xl07 conidia/ml. Comparison of
mortality results in adults of the greater wax moth at 2x104 conidia/ml revealed that infection
of over 90% could be achieved in 13 days after inoculation. Similar comparison with the
adults of the lesser wax moth showed that over 78% mortality could be achieved by day 8 after
treatment except isolate IMI33089 that caused low mortality of 67.05%. Comparison of
mortality results of the 5 larval instars of both species of wax moth at 2x10 conidia/ml
showed varying degrees of virulence among the fungal isolates. With the 5th larval instars of
the greater wax moth, isolate IITA 18 caused percentage mortality of 68.52% while with
isolates DLCO-AA-5 and DLCO-AA-14 a cumulative percentage mortality of 6 1.11% was
recorded in the lesser wax moth by day 14 of post treatment. Low mortality in the 5th larval
instars of both species was recorded with isolate IMI 330189, With the greater wax moths 5
larval instars, mortality in the control was less than 2 % while in the lesser it was less than 4%.
Results on percentage emergence of the adults from pupae of the greater wax moth adults
showed no significant difference (P > 0.05) between the different fungal isolates and controls.
With the lesser wax moth a slight difference in emergence of adults from pupae was observed
between 2x10 conidia/ml and the controls. With all fungal isolates and concentrations used,
percentage emergence of over 86.1% was observed in the greater and lesser adults. This
showed that, the isolates at the different fungal concentrations had no effect on adult
emergence when applied on the 6th instars. Laboratory experiments were also conducted to
investigate host specificity of two isolates of Metarhizium spp (DLCO-AA-83 and IMI
330189) and 1 Beauverici spp (IITA 18) all deuteromycete entomopathogenic fungi that were tested as entomopathogenic agents against the honeybees
( Apis mellifera (Ethiopian race). Each isolate was applied topically by spraying 10ml of 2x107
conidia/ml into the beehives. Isolate IITA 18 caused 0.5% mortality of the treated surface
sterilized honeybees, isolate DLCO-AA-83 resulted in 1% mortality of the treated surface
sterilized honeybees and isolate IMI 330189 had no effect on the honeybees. In cases were
infection with the applied fungal isolates occurred, fungal growth on the cadavers was
observed after surface sterilization. Therefore, the present study confirm the pathogenicity of
all the tested isolates against the adults of the greater and lesser wax moths and 4 of these
isolates in i.e. isolates in degree of virulence. Isolates IITA 18, DLCO-AA-14, DDLCO-AA-5
and D LCO-AA-83 for the greater wax moth while isolates DLCO-AA-5, DLCO-AA-14 &
DLCO-AA-83 and isolate IITA 18 for the lesser 5th larval instars as potential microbial control
agents for the management of the greater and lesser wax moths. |
