© Benaki Phytopathological Institute
Toxicity of insecticides to
Calliptamus barbarus barbarus
45
of live and dead insects was conducted eve-
ry 24 hours. An insect was considered dead
if no movement was observed after a gentle
disturbance. The bioassays were conduct-
ed in chambers in which the humidity was
65±5% and the temperature 25±1
ο
C. Cool
fluorescent light provided a photoperiod of
16: 8 light: dark. There were 8 replicates for
each treatment.
Statistical analysis
Data obtained from the bioassays on
nymphs and adults of
C. barbarus barbarus
were analyzed using Kruskal-Wallis H-test
and comparison of means were performed
with Mann-Whitney U-test for
P
=0.05. The
statistical analysis was conducted using the
software Statistica 7 (StatSoft Inc., 2004).
Moreover, the data of bioassays were sub-
jected to probit analysis to calculate the le-
thal time required for 50% (LT
50
) and 90%
(LT
90
) of the insects after their exposure to
the treated leaves for 48 hours. The analy-
sis was performed using the software SPSS
14.0 (SPSS, 2004).
Results
Bioassays on nymphs of Calliptamus bar-
barus barbarus
Significant statistical differences were
found between the toxicity of the tested in-
secticides on nymphs of
C. barbarus barbar-
us
in all the days of the experiment (Kruskal
Wallis H-test). The highest level of mortali-
ty was caused by spinosad, followed by im-
idacloprid and alpha cypermethrin (Ta-
ble 1). One day after treatment, exposure
to spinosad, imidacloprid and alpha cyper-
methrin resulted in 60.9%, 42.2% and 25%
mortality of nymphs, respectively, while
ten days after treatment the mortalities ob-
tained from the insecticides were 98.5%,
89.1% and 81.3%, respectively.
The mortalities from the insecticides
were greater than that obtained from the
water control, in all days of the trial. One day
after treatment, 3.1% and 1.6%mortality was
observed in nymphs exposed to difluben-
zuron and azadirachtin, respectively, which
did not significantly differ from the level ob-
tained from the water control. Ten days af-
ter treatment the mortalities obtained from
these insecticides were 53.1% and 29.7% and
were significantly higher than the level ob-
tained from the water control. The mortality
of grasshopper nymphs that was observed
after their exposure to diflubenzuron was
different from the mortality obtained from
the water control the last six days of the trial,
while those of azadirachtin was greater than
that of the control only the last day of the tri-
al (Table 1).
The LT
50
and LT
90
values
for nymphs of
C.
barbarus barbarus
, when the insects were
exposed to the treated leaves for 48h var-
ied from 0.83 to 15.79 days and from 3.3 to
35.02 days, respectively (Table 2). The short-
est time to kill the 50% as well as the 90% of
the grasshopper nymphs was recorded after
their exposure to spinosad followed in as-
cending order by imidacloprid, alpha cyper-
methrin, diflubenzuron and azadirachtin.
Bioassays on adults of Calliptamus bar-
barus barbarus
The toxicity of the tested insecticides on
adults of
C. barbarus barbarus
differed signif-
icantly between the insecticides in all days
of the experiment (Kruskal-Wallis H-test).
The highest level of mortality of the grass-
hopper adults was observed after their ex-
posure to spinosad followed by the mor-
talities obtained from imidacloprid, alpha
cypermethrin and lambda cyhalothrin. One
day after treatment, exposure to these in-
secticides resulted in 48.4%, 28.1%, 7.8%
and 4.7% mortality of adults respective-
ly, while ten days after treatment the rela-
tive numbers were 98.4%, 71.9%, 67.2% and
43.8%. The mortalities obtained from all in-
secticides were greater than that from the
water control in all the days of the trial, with
the exception of lambda cyhalothrin on the
first day (Table 3).
The LT
50
and LT
90
values for adults of
C.
barbarus barbarus
, when the insects were
exposed to the treated leaves for 48h, var-
ied from 0.97 to 12.51 days and from 3.18
