© Benaki Phytopathological Institute
Toxicity of insecticides to
Calliptamus barbarus barbarus
47
to 107.41 days, respectively (Table 4). The
shortest time recorded to kill the 50% and
the 90% of the adult grasshoppers was that
after their exposure to spinosad, followed
by imidacloprid and alpha cypermethrin
whereas lambda cyhalothrin showed the
slowest action of all insecticides.
Discussion
The results of the present study showed
that azadirachtin had a minimal toxicity to
nymphs of
C. barbarus barbarus
. The mor-
tality induced by this insecticide reached
the level of less than 30% and it was great-
er than that obtained from the water control
only 10 days after treatment. Similar conclu-
sions about the effectiveness of this insec-
ticide for the control of
Melanoplus differen-
tialis
Thomas (Orthoptera: Acrididae) have
been reported by Amarasekare and Edelson
(2004) although higher dose had been used
in their experiments.
Diflubenzuron had a moderate toxicity
by causing approximately 50% mortality in
nymphs of
C. barbarus barbarus
10 days after
treatment. Significant difference in the mor-
tality of grasshopper nymphs obtained by
their exposure to diflubenzuron compared
to the mortality obtained from the water
control was observed after the fourth day
after treatment. Ingestion of diflubenzuron
by immature insects results in disruption of
chitin formation and deposition that affects
the cuticle and the molting process (Wei-
land
et al.
, 2002). For this reason it is possi-
ble that diflubenzuron will be more toxic in
higher temperatures when molting rates in-
crease (Lactin and Johnson, 1995). From the
insecticides tested, diflubenzuron and aza-
dirachtin were also those that required the
longest time to kill the 50% of the grasshop-
per exposed population and particularly
long time to kill the 90% of the insects. Wei-
land
et al.
(2002) reported that the use of dif-
lubenzuron resulted in maximum control of
Acrididae, 14 days after its application in a
field experiment. Similar results about the
effectiveness of diflubenzuron on the con-
trol of nymphs of
M. differentialis
have also
been reported by Amarasekare and Edelson
(2004).
The pyrethroid insecticide alpha cyper-
methrin showed high toxic effect and rel-
atively high speed of action to
C. barbar-
us barbarus
nymphs and adults. However,
lambda cyhalothrin showed a moderate
toxicity and a slower action than the other
insecticides on the grasshopper adults. In
contrast with our results, Reinert
et al.
(2001)
reported very good efficacy of lambda cy-
halothrin on the control of
M. differentialis
adults but the dose they used was higher
than the dose used in the present study.
Spinosad exhibited the most rapid ac-
Table 2.
Lethal time of 50% (LT
50
) and 90% (LT
90
) of nymphs of
Calliptamus barbarus barbarus
when exposed for 48 hours to grapevine leaves treated with different insecticides.
Treatment
Slope (b) ±
S.E.
LT
50
α
(Days)
95% confidence
limits
LT
90
α
(Days)
95% confidence
limits
df
X
2
P
Spinosad
2.14
±
0.26 0.83 0.48 – 1.16
3.3
2.67 – 4.18 78 108.8 0.012
β
Imidacloprid 1.68
±
0.20 1.89 1.39 – 2.34 10.89 8.62 – 15.42 78 78.46 0.464
Alpha cyper-
methrin
1.86
±
0.22 3.26 2.51 – 3.94 15.95 11.61 – 27.49 78 125.05 0.001
β
Diflubenzuron 2.48
±
0.34 9.16 7.38 – 13.78 30.14 17.98 – 113.48 78 211.79 <0.0001
β
Azadirachtin 3.70
±
1.19 15.79 11.98 – 48.94 35.02 19.79 – 414.05 78 40.93 1.000
α: LT
50
and LT
90
are considered different when the 95% confidence limits fail to overlap
β: Heterogeneity factors were used in the calculation of confidence
