الفهرس 
The phenomenon of cross-resistanceOnly 14 pages are availabe for public view
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Abstract
The main part of this study was to throw a beam of light on the biochemical mechanism of Aphis gossy pii-resistance to insecticides. Three resistant strains of this insect were selected by using pirimicarb, cyanophos and alphamethrin as a carbamate , OP and pyrethroid insecticides consequently. The cross resistance spectrum of each resistant strain to 8 different insecticides was also evaluated . The activity and sensitivity of AChE were determined in the three resistant strains. Moreover the contribution of some enzymatic activities (phosphatases and non-specific esterases) in the resistance phenomena of 11. gossvpii was also bioassayed. Finally, five synergists (each at three different ratios), known as inhibitors for oxidases were used in the present study in order to select the optimum ratio and the proper synergist for overcoming the resistance phenomena in A. gossvpii. The results could be summarized in four main points as follows: I. Development of resistance of Aphis gossypii: Pirimicarb, cyanophos and alphamethrin were chosen to represent the three major groups of insecticides; carbamate, OP and pyrethroids, respectively, f o r s t u d y i n g t h e d e v e l o p m e n t of r e s i s t a n c e o f A. gossypii. The d a t a c o u l d be summarized i n t h e f o l l o w i n g p o i n t s : (1) It was o b v i o u s t h a t , a h i g h l e v e l of r e s i s t a n c e t o p i r i m i c a r b , c y a n o p h o s and a l p h a m e t h r i n of a b o u t 3 3 . 3 , 30 and 38.46 f o l d , r e s p e c t i v e l y h a d b e e n dev e l o p e d i n A. gossypii by c o n t i n u o u s s e l e c t i o n u n d e r l a b o r a t o r y c o n d i t i o n s f o r a b o u t 30 s u c c e s s i v e . - g e n e r a t i o n s . ( 2 ) Reviewing t h e o b t a i n e d r e s u l t s , it c o u l d be f a i r l y c o n c l u d e d t h e r e s i s t a n t s t r a i n s ofaphids were more h e t e r o g e n o u s i n t h e i r r e a c t i o n t o p i r i r n i c a r b , cyanophos and a l p h a r n e t h r i n s i n c e t h e i r D . H . v a l u e s were l e s s t h a n o n e . (3) Based on a c c u m u l a t e d r e s i s t a n c e r a t i o (A.R.R.) f o r t h e t h r e e i n s e c t i c i d e s from 15 t o 30 g e n e r a t i o n s , it a p p e a r e d t h a t , a f t e r 15 g e n e r a t i o n s o f s e l e c t i o n a v e r y q u i c k b u i l d up of r e s i s t a n c e was a c h i e v e d w i t h t h e c a r b a m a t e compound ( p i r i m i c a r b ) t h a n t h e o t h e r compounds. T h i s i m p l i e s t h a t t h e a c c u m u l a - t i o n and gene(s) f r e q u e n c y of p i r i m i c a r b r e s i s t a n c e i n A. gossypii was h i g h e r t h a n t h a t of t h e o t h e r t e s t e d compounds. ( 4 ) B a s e d o n t h e r e s i s t a n c e r a t i o (R.R.) f o r t h e l a t e n t p e r i o d of s e l e c t i o n , it c o u l d be c o n c l u d e d t h a t t h e r e s i s t a n c e of A. gossypii t o p y r e t h r o i d i n s e c t i c i d e may r e q u i r e r e s i s t a n c e - f a c t o r s more t h a n t h a t f o r t h e OP compound w h i l e t h e c a r b a m a t e compound m i g h t be t h e l e a s t i n t h i s r e s p e c t . Based on t h e s u s c e p t i b i l i t y f a c t o r ( S . F . ) i t c o u l d be c o n c l u d e d t h a t , b o t h p i r i m i c a r b and a l p h a m e t h r i n r a p i d l y l o s e t h e i r e f f e c t i v e n e s s on a p h i d p o p u l a - t i o n s a f t e r t h e f i r s t f i v e g e n e r a t i o n s a l t h o u g h t h e R . R . v a l u e s f o r b o t h compounds were o n l y 2.06 a n d 2.88 f o l d , r e s p e c t i v e l y . T h i s r e s u l t r e v e a l e d t h a t b o t h compounds s h o u l d n o t b e u s e d more t h a n o n c e d u r i n g t h e c o t t o n s e a s o n t o a v o i d t h e a c c u m u l a t i o n of t h e r e s i s t a n c e factor(s) t o t h e f r e q u e n c y w h i c h e n a b l e t h e s t r a i n t o d e v e l o p r e s i s t a n c e and t h u s t o a v o i d c o n t r o l f a i l u r e . On t h e o t h e r h a n d , d a t a showed t h a t t h e OP compound; c y a n o p h o s c o u l d b e r e - -used e f f e c t i v e l y u n d e r f i e l d c o n d i t i o n w i t h a t o - l e r a n c e r a t i o o f a b o u t 6 f o l d . I n o t h e r w o r d s , t h e r e s u l t s s u g g e s t e d t h a t c y a n o p h o s c o u l d b e u s e d e f f - e c t i v e l y a t e v e n a r e d u c e d r a t e t h a n t h e recommended o n e .