EFFICIENCY OF TWO NOVEL BIOTIC COMPOUNDS AGAINST THE LABORATORY AND FIELD STRAIN OF THE COTTON LEAFWORM, Spodoptera littoralis (Boisd.)

Abstract

The efficiency of two novel compounds (takumi, and radiant) and conventional insecticide (methomyl) against the second and fourth instars of the laboratory and field strains of Spodoptera littoralis was evaluated under laboratory conditions through determination their LC50 values. Radiant was the most toxic one against both of 2nd and 4th larval instars of the laboratory and field strains. The LC50values were 0.06, 1.95(2nd instar) and 5, 10 ppm (4th instar) of laboratory and field strains, respectively. Takumi was the second one with the LC50values of 0.12, 2.4 and 9.0, 19 ppm for the two instars of both strains, respectively. Lannate was the least one, its LC50values were 5.86, 10 and 46.9, 93.8ppm, respectively. All the treated larvae were biologically affected by the three tested compounds. The effect varied according to the strain, larval instars and tested compound. Therefore, the treated larvae were resulted in decreased pupation and adult emergence percentages. Also, the larval treatment of field strain treated with takumi induced the longest period of the larval duration. While, the 2nd larval instar treatments had the highest effect in the pupal period increase. Hence, the larval treatment of the laboratory strain had the strongest effect in the pupal weight decrease. The 2nd instar of the field strain treated with radiant and the 4th instar of the same strain treated with takumi caused the highest percent of pupal malformations, hence, the 2nd instar of the laboratory strain treated with methomyl and the 4th instar treated with takumi induced the greatest percent of adult malformations. Also, the 4th instar of the field strain treated with takumi had the strongest effect in adult fecundity reduction..