CONTENTS

EFFECT OF SYNERGIST, TRIPHENYL PHOSPHATE ON RESISTANT GUNTUR STRAIN
During 2008-09, the LD 50
and LD 90
values of
cypermethrin were 0.3324 and 3.6844; 0.1862 and
1.9308; 0.1224 and 0.7835 µg / larva at 24, 48 and
72 HAT, respectively. The Guntur strain of S. litura
recorded the LD 50
and LD 90
values of 0.4200 and
2.4540 µg / larva for cypermethrin alone at 72 HAT.
The synergistic factor at 72 HAT due to TPP at LD 50
and LD 90
levels was 3.43 and 3.13, respectively during
2008-09 (Table 2&3).
Methomyl + TPP
During 2007-08, the LD 50
and LD 90
values of
methomyl in combination with TPP to the third instar
larvae of Guntur strain of S. litura were 0.5724 and
5.7162; 0.3580 and 3.0340; 0.3350 and 2.8000 µg /
larva at 24, 48 and 72 HAT, respectively.
The Guntur strain of S. litura recorded the
LD 50
and LD 90
values of 0.5247 and 4.2922 µg / larva
for methomyl alone at 72 HAT. The synergistic factor
at 72 HAT due to TPP at LD 50
and LD 90
levels was
1.57 and 1.53, respectively during 2007-08 (Table
1&3).
During 2008-09, the LD 50
and LD 90
values of
methomyl were 0.3582 and 5.1174; 0.2202 and
2.3152; 0.1912 and 1.5283 µg / larva at 24, 48 and
72 HAT, respectively. The Guntur strain of S. litura
recorded the LD 50
and LD 90
values of 0.5140 and
3.5895 µg / larva for methomyl alone at 72 HAT. The
synergistic factor at 72 HAT due to TPP at LD 50
and
LD 90
levels was 2.69 and 2.35, respectively during
2008-09 (Table 2&3).
From the above results it was evident that
synergism with TPP was observed more in
cypermethrin followed by quinalphos, chlorpyriphos,
methomyl and endosulfan at LD 50
level revealing that
the levels of resistance to cypermethrin followed by
quinalphos, chlorpyriphos, methomyl and endosulfan
Table 3. Synergism in S. litura to the test insecticides during two years, 2007 – 08 and 2008 - 09
Insecticide LD 50 LD 90
Synergistic ratio
( 2007 – 08) LD 50 LD 90 (2008 – 09)
Synergistic ratio
LD 50 LD 90 LD 50 LD 90
Chlorpyriphos 0.3040 1.9340 -- -- 0.2620 1.2000 -- --
Chlorpyriphos + TPP
0.1643 0.9616 1.85 2.01 0.1596 0.6638 1.64 1.81
Quinalphos 0.3600 2.2160 -- -- 0.3500 1.7100 -- --
Quinalphos +TPP
0.1720 0.9379 2.09 2.36 0.1588 0.7571 2.20 2.26
Endosulfan 2.0425 3.3052 -- -- 1.7072 3.2882 -- --
Endosulfan + TPP
1.7190 3.0661 1.18 1.07 0.8970 1.5015 1.90 2.19
Cypermethrin 0.4700 3.1680 -- -- 0.4200 2.4540 -- --
Cypermethrin + TPP
0.2099 1.5215 2.24 2.08 0.1224 0.7835 3.43 3.13
Methomyl 0.5247 4.2922 -- -- 0.5140 3.5895 -- --
Methomyl + TPP
0.3350 2.8000 1.57 1.53 0.1912 1.5283 2.69 2.35
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