The stomach poisonous impact of some insect growth
regulators and biocides was tested under laboratory and semi-field
conditions against cotton leafworm, S. littoral/s. Obtained results
revealed that, the second instar larvae reflected higher level of
susceptibility towards all the tested insecticides than fourth one.
According to LC50 and LC90 values, chlorpyrifos was the most
effective insecticide that recorded 0.1 and 0.809 ppm for 2 instar
larvae and 0.472 and 6.838 ppm for 4th instar larvae, respectively.
Meanwhile, tebufenozide appeared to be the least effective
compound against both tested instars that gave 9.9Oland 36.447
ppm against 2 instar, whereas the LC50 and LC90 values were
65.736 and 1000.775 ppm) against the 4th one, respectively. The
rest compounds gave moderate effects in this respect.
Data concerning the initial and residual activity of the tested
insecticides, Tracer, XDE, methoxyfenozide, Dipel 2x and
chlorpyrifos against 4th instar larvae of field strain cotton leafworm,
S. littoral/s were determined. The initial effect calculated as the
cumulative mortalities at zero time recorded 100, 100, 92, 88 and
26 % for methoxyfenozide, chiorpyrifos, XDE, Tracer and Dipel 2x,
respectively. The untreated check recorded 2%, methoxyfenozide
and chlorpyrifos gave the highest significant mortalities effects
comparing to the untreated, Chlorpyrifos and methoxyfenozide
were detected the highest significant mortalities effect as general
residual effect whereas Dipel 2x recorded the least significant
mortality effect, which it being 18.40% as compared to other
insecticides.
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