Field Persistence of Some Novel Insecticides Residues on Cotton Plants and Their Latent Effects against Spodoptera littoralis (Boisduval)

New insecticides that exhibited high compatibility with environment components are very promising substitutes for control of the economic insects. Simi-field experiments were conducted on profenofos and four novel insecticides viz., spinosad, emamectin-benzoate, pyridalyl and indoxacarb to investigate their efficiency and the field persistence of their residues against 4 instar larvae of the cotton leaf worm, Spodoptera littoralis (Boisd.), field strain via determination of Lt50 values. The recommended rates of these insecticides were sprayed on the foliage of cotton plants, var. Giza 86, in the field. Also, latent effects after feeding of larvae on sprayed leaves for 24 h were studied under laboratory conditions. Pyridalyl and emamectinbenzoate had significantly the most persistent residual activity with Lt50 values of 6.74 and 5.51days, respectively. Whereas, indoxacarb, spinosad and profenofos displayed inferior persistence periods translated in Lt50 values of 0.72, 1.33 and 1.55 days, respectively. The high efficiency of pyridalyl and emamectin-benzoate decreased gradually after spray causing 100, 100, 95, 87, and 72% larval mortality for pyridalyl and 100, 92, 88, 66, and 41% larval mortality for emamectin-benzoate after 0, 1, 2, 4, and 6 days of spray, respectively. Two days post spray, the toxic effect of profenofos declined sharply recording 94, 60, 45, 30, and 10% larval mortality after 0, 1, 2, 4, and 6 days of application, respectively. As the time after spray extended, the latent effects of the tested insecticides on survived larvae and consequent stages significantly decreased. Pyridalyl and emamectin-benzoate resulted in the superior latent effects even at the 6 day of spray; causing larval duration of 20.1 & 19.6 days, 20.4 & 42.6% normal pupae and 26.7 & 55.2% normal adult emergence, respectively comparing to the other treatments. These results indicated that novel insecticides had the potentiality to be promising substitutes of conventional toxicants for S. littoralis control under field conditions.