<p>Tobacco caterpillar, <italic>Spodoptera litura</italic> is a polyphagous insect causing extensive damage to several agricultural and horticultural crops. If not controlled timely, the pest may completely devour the leaves of infested plant resulting in huge crop losses. Wide range of insecticides used against this pest has resulted in development of resistance (<xref ref-type="bibr" rid="bib005">Mathirajan & Regupathy, 2002</xref>; <xref ref-type="bibr" rid="bib003">Chalam <italic>et al.</italic>, 2003</xref>). Hence, the present study on the toxicity of certain new molecules against <italic>S. litura</italic> was undertaken.</p><p><italic>S. litura</italic> egg masses and larvae were collected from cotton host plants at three locations (Bathinda, Mansa & Ferozepur districts i.e. cotton belt) in Punjab state during April-October, 2005. Insects were reared on fresh castor leaves in B.O.D. incubator maintained 27±2°C and 78±2% R.H. Serial dilutions of following commercial grade formulations <italic>viz.</italic>, pyridalyl (S 1812 10EC, Sumitomo Chemicals Ltd.) emamectin benzoate (Proclaim 5 SG, Syngenta India Ltd.), indoxacarb (Avaunt 15SC, EI Dupont India Pvt. Ltd.), spinosad (Tracer 48 SC, De-Nocil Crop Protection Ltd.) and chlorpyriphos (Dursban 20EC, De-Nocil Crop Protection Pvt. Ltd.) were prepared in water. Bioassays were conducted on 3<sup>rd</sup> instar larvae (7±1 day old & 30–40 mg weight) of F<sub>1</sub> generation using leaf dip disc residue technique. The mortality data was recorded at 24 and 48 hrs after treatment. The data was subjected to Probit Analysis after <xref ref-type="bibr" rid="bib001">Abbott's correction (Abbott, 1925</xref>).</p><p>LC<sub>50</sub> values of pyridalyl, emamectin benzoate, indoxacarb, spinosad and chlorpyriphos were worked out to be 0.00004, 0.000004, 0.00001, 0.0006 and 0.015%, respectively (<xref ref-type="table" rid="tab001">Table 1</xref>). By taking LC<sub>50</sub> value of least toxic insecticide with highest LC<sub>50</sub> value i.e. chlorpyriphos to be unity. The ascending order of relative toxicity was found to be 2, 375, 1500 and 3750 for spinosad, pyridalyl, indoxacarb and emamectin benzoate, respectively. Emamectin benzoate is a novel semi-synthetic derivative of the natural product was found to be most toxic. High toxicity of emamectin benzoate with LC<sub>50</sub> value 0.0015% was reported by Stanley <italic>et al.</italic> (<xref ref-type="bibr" rid="bib006">2006</xref>). The next highly toxic insecticide was spinosad. Similar results were also observed by Boomathi <italic>et al.</italic> (<xref ref-type="bibr" rid="bib002">2006</xref>). <table-wrap id="tab001"><label>Table 1</label><caption><p>Toxicity of insecticides against <italic>Spodoptera litura</italic></p></caption><table><thead><tr><th rowspan="3">Insecticides</th><th colspan="2" align="center">Heterogeneity</th><th rowspan="3" align="center">LC (%)<sup>50</sup></th><th rowspan="3" align="center">Fiducial limits</th><th rowspan="3" align="center">Regression equation</th><th rowspan="3" align="center">Toxicity ratio</th></tr><tr><th colspan="2"><hr /></th></tr><tr><th align="center">d.f.</th><th align="center">χ<sup>2</sup></th></tr></thead><tbody><tr><td colspan="7"><hr /></td></tr><tr><td valign="top">Pyridalyl</td><td align="center" valign="top">7</td><td align="center" valign="top">0.01859</td><td align="center" valign="top">0.00004</td><td align="center" valign="top">0.00003–0.00006</td><td align="center" valign="top">10.65953+1.28934x</td><td align="center" valign="top">375.00</td></tr><tr><td valign="top">Emamectin benzoate</td><td align="center" valign="top">8</td><td align="center" valign="top">0.01702</td><td align="center" valign="top">0.000004</td><td align="center" valign="top">0.000003–0.000006</td><td align="center" valign="top">12.44581+1.36482x</td><td align="center" valign="top">3750.00</td></tr><tr><td valign="top">Indoxacarb</td><td align="center" valign="top">8</td><td align="center" valign="top">0.05457</td><td align="center" valign="top">0.00001</td><td align="center" valign="top">0.00001–0.00002</td><td align="center" valign="top">16.05415+2.25948x</td><td align="center" valign="top">1500.00</td></tr><tr><td valign="top">Spinosad</td><td align="center" valign="top">8</td><td align="center" valign="top">0.02185</td><td align="center" valign="top">0.00600</td><td align="center" valign="top">0.00443–0.00875</td><td align="center" valign="top">7.94769+1.33002x</td><td align="center" valign="top">2</td></tr><tr><td valign="top">Chlorpyriphos</td><td align="center" valign="top">6</td><td align="center" valign="top">0.04000</td><td align="center" valign="top">0.01500</td><td align="center" valign="top">0.01100–0.01900</td><td align="center" valign="top">8.30600+1.80100x</td><td align="center" valign="top">1</td></tr></tbody></table></table-wrap></p></sec></body><back><ref-list><title>References

APPS

Annals of Plant Protection Sciences

0971-3573

Society of Plant Protection Sciences

apps-15-1-056

SHORT COMMUNICATION

Relative Toxicity of New Insecticides against Spodoptera litura

Dhawan

A.K.

Kaur

Ashwinder

Kumar

Ravinder

Department of Entomology, P.A.U., Ludhiana 141 004, India. Email: batthscorpion@rediffmail.com.

32007

151238239

<p>Tobacco caterpillar, <italic>Spodoptera litura</italic> is a polyphagous insect causing extensive damage to several agricultural and horticultural crops. If not controlled timely, the pest may completely devour the leaves of infested plant resulting in huge crop losses. Wide range of insecticides used against this pest has resulted in development of resistance (<xref ref-type="bibr" rid="bib005">Mathirajan & Regupathy, 2002</xref>; <xref ref-type="bibr" rid="bib003">Chalam <italic>et al.</italic>, 2003</xref>). Hence, the present study on the toxicity of certain new molecules against <italic>S. litura</italic> was undertaken.</p><p><italic>S. litura</italic> egg masses and larvae were collected from cotton host plants at three locations (Bathinda, Mansa & Ferozepur districts i.e. cotton belt) in Punjab state during April-October, 2005. Insects were reared on fresh castor leaves in B.O.D. incubator maintained 27±2°C and 78±2% R.H. Serial dilutions of following commercial grade formulations <italic>viz.</italic>, pyridalyl (S 1812 10EC, Sumitomo Chemicals Ltd.) emamectin benzoate (Proclaim 5 SG, Syngenta India Ltd.), indoxacarb (Avaunt 15SC, EI Dupont India Pvt. Ltd.), spinosad (Tracer 48 SC, De-Nocil Crop Protection Ltd.) and chlorpyriphos (Dursban 20EC, De-Nocil Crop Protection Pvt. Ltd.) were prepared in water. Bioassays were conducted on 3<sup>rd</sup> instar larvae (7±1 day old & 30–40 mg weight) of F<sub>1</sub> generation using leaf dip disc residue technique. The mortality data was recorded at 24 and 48 hrs after treatment. The data was subjected to Probit Analysis after <xref ref-type="bibr" rid="bib001">Abbott's correction (Abbott, 1925</xref>).</p><p>LC<sub>50</sub> values of pyridalyl, emamectin benzoate, indoxacarb, spinosad and chlorpyriphos were worked out to be 0.00004, 0.000004, 0.00001, 0.0006 and 0.015%, respectively (<xref ref-type="table" rid="tab001">Table 1</xref>). By taking LC<sub>50</sub> value of least toxic insecticide with highest LC<sub>50</sub> value i.e. chlorpyriphos to be unity. The ascending order of relative toxicity was found to be 2, 375, 1500 and 3750 for spinosad, pyridalyl, indoxacarb and emamectin benzoate, respectively. Emamectin benzoate is a novel semi-synthetic derivative of the natural product was found to be most toxic. High toxicity of emamectin benzoate with LC<sub>50</sub> value 0.0015% was reported by Stanley <italic>et al.</italic> (<xref ref-type="bibr" rid="bib006">2006</xref>). The next highly toxic insecticide was spinosad. Similar results were also observed by Boomathi <italic>et al.</italic> (<xref ref-type="bibr" rid="bib002">2006</xref>). <table-wrap id="tab001"><label>Table 1</label><caption><p>Toxicity of insecticides against <italic>Spodoptera litura</italic></p></caption><table><thead><tr><th rowspan="3">Insecticides</th><th colspan="2" align="center">Heterogeneity</th><th rowspan="3" align="center">LC (%)<sup>50</sup></th><th rowspan="3" align="center">Fiducial limits</th><th rowspan="3" align="center">Regression equation</th><th rowspan="3" align="center">Toxicity ratio</th></tr><tr><th colspan="2"><hr /></th></tr><tr><th align="center">d.f.</th><th align="center">χ<sup>2</sup></th></tr></thead><tbody><tr><td colspan="7"><hr /></td></tr><tr><td valign="top">Pyridalyl</td><td align="center" valign="top">7</td><td align="center" valign="top">0.01859</td><td align="center" valign="top">0.00004</td><td align="center" valign="top">0.00003–0.00006</td><td align="center" valign="top">10.65953+1.28934x</td><td align="center" valign="top">375.00</td></tr><tr><td valign="top">Emamectin benzoate</td><td align="center" valign="top">8</td><td align="center" valign="top">0.01702</td><td align="center" valign="top">0.000004</td><td align="center" valign="top">0.000003–0.000006</td><td align="center" valign="top">12.44581+1.36482x</td><td align="center" valign="top">3750.00</td></tr><tr><td valign="top">Indoxacarb</td><td align="center" valign="top">8</td><td align="center" valign="top">0.05457</td><td align="center" valign="top">0.00001</td><td align="center" valign="top">0.00001–0.00002</td><td align="center" valign="top">16.05415+2.25948x</td><td align="center" valign="top">1500.00</td></tr><tr><td valign="top">Spinosad</td><td align="center" valign="top">8</td><td align="center" valign="top">0.02185</td><td align="center" valign="top">0.00600</td><td align="center" valign="top">0.00443–0.00875</td><td align="center" valign="top">7.94769+1.33002x</td><td align="center" valign="top">2</td></tr><tr><td valign="top">Chlorpyriphos</td><td align="center" valign="top">6</td><td align="center" valign="top">0.04000</td><td align="center" valign="top">0.01500</td><td align="center" valign="top">0.01100–0.01900</td><td align="center" valign="top">8.30600+1.80100x</td><td align="center" valign="top">1</td></tr></tbody></table></table-wrap></p></sec></body><back><ref-list><title>ReferencesAbbott

W.S.

(1925) A method of computing effectiveness of an insecticide. J. Econ. Ent., 18: 265–267.Boomathi

Sivasubramanian

Raguraman

(2006) Toxic effects of spinosad and its combination with other microbial insecticides against Helicoverpa armigera. Ann. Pl. Protec. Sci., 14: 228–229.Chalam

M.S.V.

Rao

G. Rama Chandra

Chinnabba

(2003) Insecticide resistance and its management in cotton aphid in Guntur district. Ann. Pl. Protec. Sci., 11: 228–231Finey

D.J.

(1971) Probit Analysis. Third editionCambridge University, Press, London, pp 318.Mathirajan

V.G.

Regupathy

(2002) Toxicity of thiamethoxam to Aphis gossypii. Amarasca devastanis Nilaparvata lugens and Sogotella furcifera. Ann. Pl. Protec. Sci., 10: 369–370.Stanley

Chandrasekaran

Regupathy

Jasmine

R. Sheeba

(2006) Base line toxicity of emamectin and spinosad to Spodoptera litura. Ann. Pl. Protec. Sci., 14: 346–349.