Laboratory tests were conducted to determine the efficien~ of Abamectin
1.8% EC, Xentari 10.3% Granule and MVPII 20% FL against the 2" instar larvae of
Monofia, Gharbya and Sehera field strains of the cotton leafworm Spodoptera /ittora/is
. Manshiat Ganzor, Ewasna and Etay EI-Sarod water were used for dilution of the
biocides concentrations and were tested against for Gharbya, Monofia and Sehera
strains. The results indicate that Abamectin at the different concentrations caused
high mortality after 14 days to the 2nd instar larvae of the three tested field strains. All
larvae tested failed to reach successful pupation. Sehera cotton leafworm strain was
the most susceptible to MVPII while Monofia strain was the least. The L T 50 "s for
Monofia, Sehera and Gharbya strains were 7.46, 2.70 and 4.69 days at the
concentration of 10. OOml/L. The data also revealed that the 2"d instar larvae of Sehera
strain was more susceptible to Xentari than the larvae of Monofia and Gharbya. The
L T 50 • S were 2.44, 1.99 and 4.74 days at the concentration of 0.6m1/L for Monofia,
Sehera and Gharbya strains, respectively. Data showed that pH, conductivity and salinity for Sehera (Etay EI-Barod)
water were higher than that of Gharbya (Manshiat Ganzor) and Monofia (Ewasna)
water. The usage of Sehera water for dilution resulted in increasing the toxicity of the
tested biocides for the larvae of the cotton leafworm. This phenomenon can be
benefits since the great majority of waters used for dilution in Egypt are alkaline.
Increasing in toxicity as a result of increasing conductivity may be due to augmenting
penetration of the toxicant.