الفهرس 
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Abstract
The present studies include laboratory and field investigations.
Firstly the laboratory studies aims to evaluate the toxicity of five recent plant extracts in laboratory against egg and larval stages of the pink bollworm, Pectinophora gossypiella ( Saund. ) and the cotton leafworm, Spodoptera littoralis ( Boisd. ). Also, the latent effects of the tested extracts on certain biological aspects were studied. Later on, the population analysis of bollworms, pink and spiny was studied under field conditions during 2003 and 2004 cotton growing seasons in an attempt to contribute the best placement of either insecticides or / and plant extracts as control measure instead of classical conventional applications. Simultaneously the fluctuation of larvae (in green bolls) of bollworms P. gossypiella_and E. insulana was also studied in the same seasons. In addition, the five plant extracts and non traditional pest control agents were field investigated against cotton bollworms , P. gossypiella and E. insulana_and two sucking pests, Emboasca _spp and Aphis gossypii. Also, the five experimental materials were arranged in 6 different sequential systems and investigated against bollworms during 2004 aand 2005 cotton seasons in compare with the official governmental program (RPMA). Finally, the effect of different investigated treatments on losses of cotton yield caused by bollworms infestigation was calculated using mathematical modle on field data. The obtained data of the forementioned tested topics could be summarized as follow:
1.1. Evaluation of toxicity against cotton leafworm S. littoralis ( Boisd. ) 1.1.1. Ovicidal effects of plant extracts against egg stage:
Laboratory bioassay of the 5 plant extracts using dipping technique revealed that Bioneem extract exhibited the highest ovicidal activity against egg stage of S. littoralis_and was followed by Garlic, Rosemary, Marjorum and Thymus, respectively. Exposure and fe with LCso values of all signilic3I1tly pllpa/ioJ) abnormality. Similarly, low percent of adult e percent deformed adults
1.1.2. Larvicidal effect of plant extracts against larval stage:
Laboratory bioassay using 2nd instar larvae of s.. littoraUs indicate that extracts of Bioneem, Garlic and Rosemary recorded almostly similar and relatively the highest larvicidal activity compared with Marjorum and Thymus extracts. However, the tested extracts exhibited larvicidal activity, arranged in the same order against the 4th instar larv,of S. littoralis_, when fed for 24 h on castor oil leaves treated with extracts. extrac Likewise, pupati the 2nd instar larvae on Thymus was signifi . pupae percent was si check. However, Bi emergence and iner other extracts and un 1.2. Evaluation of toxicity against pink bollworm P. gossvpiella 1.2.1. Ovicidal effect of plant extracts against egg stage:
Lcso values based on laboratory bioassay, adapting dip technique, indicated that there was no significant difference between the tested extracts against pink bollworm egg stage. 1.2.2. Larvicidal effect of plant extracts against larval stage: Toxicity data against pink bollworm 2nd instar larvae revealed Bioneem extract was relatively the highest effective while Thymus was the least effective whereas other extracts came in between.
2. Field studies 2.1. Pupation dyn 2.1.1. Population dyn Data of delta s’ the population density another forming five tested extracts on certain biological aspects. 1.3.1. Latent effects in S. littoralis surviving treatment with extracts: 2.1.2. population dy As for spiny bo observed during 200 during 2004 cotton s Exposure and feeding S.)ittoralis 2nd instar larvae on leaves treated with LCso values of all tested extracts except Thymus resulted in reducing significantly pupation percentages and resulted insignificantly high pupal abnormality. Similarly, all extracts except Thymus exhibited significantly low percent of adult emergence as well as remarkable and significant percent deformed adults. e: alis
1.3.2. Latent effects in P.gossypiella surviving treatment with extracts: stly with ited Likewise, pupation percentages of P.J5ossypiella surviving feeding the 2nd instar larvae on sublethal (LCso) cone. of all tested extracts except Thymus was signific~ntly affected (reduced) and also the deformed pupae percent was significantly affected (increased) compared with check. However, Bioneem and Garlic reduced significantly adult emergence and increased significantly deformed adults compared with other extracts and untreated check whereas Thymus was the least in this respect.
2. Field studies
2.1. Pupation dynamic of cotton bollworms
2.1.1. Population dynamic of pink bollworm P. gossypiella.