COMPARATIVE TOXICITY OF THREE NOVEL BIOTIC COMPOUNDS , SPINOSAD PYRIDALYL AND RADICAL IN RELATIVE TO A CONVENTIONAL INSECTICIDE, LANNATE AGAINST THE FIELD AND LABORATORY STRAIN OF THE SECOND AND FOURTH INSTAR LARVAE OF COTTON LEAFWORM, Spodoptera Littoralis (BOISD.)

Abstract

The toxic activity of three novel compounds( Pyridayl, Radical, Spinosad) and conventional insecticide( Lannate)against the second and fourth instars of the Lab. and Field strains of Spodoptera littoralis. was evaluated under laboratory conditions through determination their LC50 values.` Radical was the most toxic one against both of 2nd and 4th instar larvae of the lab. and field strains . The LC50values were 1.1 , 2.7 and 1.95 , 4.4 ppm for both second and fourth instar larvae of the two lab. and field strains , respectively . Pyridalyl was the second one with the LC50values of 1.8 , 5 and 6.2 , 9.4 ppm for the two instars of both strains, respectively. Lannate was the third one ,its LC50values were 3.9, 6 and 11,19ppm for both instars of the strains , respectively. While , Spinosad was the fourth one, its LC50values were 21, 62.5 and 31.3 and 130 ppm for both instars of the strains, respectively. All the treated larvae were biologically affected by the four tested compounds . The effect varied according to the strain , larval instar and tested compound. Therefore ,the treated larvae were significantly affected and resulted in decreased pupation and adult emergence percentages. While , Pyridalyl treatment had the strongest effect in larval duration, pupal and adult malformations increase, adult fecundity ,fertility and longevity decrease in case of larval treatment of the two instars of both strains , and it had the highest effect in pupal duration increase and weight decrease in case of treatment of the second instar of the field strain with this compound, and it was effective against the sex ratios, it induced the males increase and females decrease, as respect to control, with the treatment of fourth instar of lab. strain . Whereas, Radical ,had the greatest effect on adult fecundity and fertility with the of fourth instar treatment of field strain .Also it was effective against the pupal weight with the treated second instar of field strain and it had the highest effect on larval duration and adult malformations in case of the treatment of the second and fourth instars of lab strain .However, it had an adversely effect on the sex ratio (it caused males decrease and females increase) with the treatment of fourth instar of field strain. Spinosad had the highest effect on both adult fecundity and fertility with the treated fourth instar of field strain and it induced the strongest effect of adult malformations with the treatment of both instars of lab. strain , and it affect the sex ratio, lead to males increase and females decrease with the treatment of fourth instar of lab .strain. Lannate , had the highest effect on pupal malformations with the larval treatment of both instars of both strains ,and it was effective on pupal weight and adult malformations with the treatment of either second or second and fourth instar together of field strain ,also, it was effective on adult fecundity, fertility and longevity with the treated fourth instar of field strain and it had the strongest effect on larval duration with the treatment of the fourth instar of the lab. strain .