Page 43 - Volume 2, Issue 1, January 2009
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Michaelakis
et al.
44
© Benaki Phytopathological Institute
egg rafts are used is shown in Figure 1
where mortality percentage is presented for
every larval instar and pupa stage. From the
results it is clear that temephos killed all the
first and second larval instars (100%mortali-
ty) whereas pyriproxyfen did not significant-
ly differ from the control for the first to the
fourth larval instars. In Table 1 adult stage
emergence is presented for the control and
each insecticide.
Pyriproxyfen was also found to be statis-
tically highly effective in the stage of pupa
with a mortality ranging from 80% to 95%
and proved to be a useful tool for the con-
trol of
Cx. pipiens.
The results are in agree-
ment with the already known mode of ac-
tion of pyriproxyfen, even though egg rafts
were used instead of larvae of 3
rd
or late 4
th
instar (20).
Regarding the oviposition bioassays,
results for a period of 6 days are shown in
Figure 2. For the first two days pyriproxy-
fen showed a rather repelling action but
the rest four days of the experiment the at-
traction level reached almost control lev-
els. However, as similar effect of pyriproxy-
fen on the gravid females mosquitoes is not
known further study needs to be conduct-
ed. On the contrary, temephos did not seem
to affect oviposition during the 6-day peri-
od.
In conclusion, pyriproxyfen and teme-
phos, as shown in Table 1, revealed the same
results for a period of 6 days and the only dif-
ference was the mode of action of each lar-
vicidal. Pyriproxyfen residual activity with
egg rafts for at least one week period was
very hopeful for the aims of this study, which
was to investigate if pyriproxyfen could be
used instead of temephos in integrated con-
trol programs with other means of mosquito
control, such as oviposition attractants. While
a simple contact with temephos was enough
to kill the larvae and oviposition pattern did
not affected, pyriproxyfen needs more time
and is also repellant for gravid mosquitoes.
Previous work indicated that the com-
bination of temephos with the pheromone
could result in the implementation of the
attract-and-kill strategy (12). Further re-
search is needed to evaluate the effective-
ness of pyriproxyfen and its utility as larvici-
dal agent. Moreover, additional knowledge
when pyriproxyfen combine with phero-
mone would allow the effectively practical
application in larval breeding sites such as
rain water collection areas, artificial contain-
Figure 2.
Oviposition effected by temephos and pyriproxyfen.
The dashed lines represent the upper and lower values of the
control mean ± SE (50.1 ± 2.1%, n=10).
Table 1.
Adult emergence of Control, py-
riproxyfen (P) and temephos (T) against
hatched larvae of
Cx. pipiens
biotype
moles-
tus
for every post treatment day
.
Day
Treatment
Control
P
T
1
82.7% 0.0% 0.0%
2
86.1% 0.0% 0.0%
3
85.1% 1.2% 0.0%
4
83.5% 0.6% 0.0%
5
94.0% 0.0% 0.0%
6
86.5% 0.0% 0.0%
Figure 1.
Percentage mortality for the control (C), py-
riproxyfen (P) and temephos (T) at the 1st and 2nd larval in-
star [L(1+2)], 3rd and 4th larval instar [L(3+4)] and at pupal
stage.
