Influence of Two Insect Growth Regulators on Chitinase Activity | ||||
| Alexandria Journal of Agricultural Sciences | ||||
| Article 8, Volume 60, Issue 3, May 2015, Page 303-307 PDF (394.83 K) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/alexja.2015.31262 | ||||
 View on SCiNiTO | ||||
| Authors | ||||
| M. Ismail Seham1; Shaker N.2 | ||||
| 1Central Laboratory of Pesticides, Sabahia, Alexandria, A.R.C., Egypt | ||||
| 2Pesticide Chemistry Dept., Fac. Agric., Alex. Univ., Egypt | ||||
| Abstract | ||||
| Toxicity of two insect growth regulators (IGRs) (lufenuron and hexaflumuron) against two larval instars of cotton leafworm Spodoptera littoralis, laboratory and field strains were determined. Chitinase activity in the two strains also was investigated. Results revealed that, 2nd instar larvae were more sensitive than 4th instar larvae to both insecticides. The sensitivity of chitinase activity was measured by I50 values. The I50 values of lufenuron were 0.31, and 0.64 µM for lab and field strains of S. littoralis 2nd larvae respectively, while I50 values were 0.44, and 0.75 µM for lab and field strains of S. littoralis 4th larvae respectively. The hexaflumuron were 0.57, and 0.76 µM for lab and field strains of S. littoralis 2nd larvae respectively, the I50 values were 0.65, and 0.81µM for lab and field strains of S. littoralis 4th larvae respectively. Also, chitinase enzyme kinetic parameters, as Michaelies-Menten Kinetics (Km and Vmax) values and the inhibition constant (Ki) were determined. The obtained data proved that lufenuron and hexaflumuron compounds are competitive inhibitors of chitinase activity. Results indicated that, the IGRs have shown high potentiality against larvae of S. littoralis, so, these IGRs may be recommended for S. littoralis larvae control, it could be concluded that the use of IGRs instead of conventional hazardous insecticides; may avoid increasing selection pressure of S. littoralis populations to conventional insecticides, hazard effects on human health, environmental components and natural enemies, IGRs may play an important role in future insect pest management programs. | ||||
| Keywords | ||||
| Critical period – Weed; Competition – Sunflower | ||||
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