Abstract :
Ten cotton varieties and genotypes, Giza 70, Giza 85, Giza 86, Giza 92, Alexandria 4, Bahteem 101, Karshensky 2, Pima S 6, Pima S 6 x G. 89 and Seuvin were evaluated for their relative resistance against chewing insect pests i.e., Pectinophora gossypiella (Sound.), Earias insulana (Boisd.) and Helicoverpa armigera (Hub.) in Egypt. The study was conducted at Sakha Agricultural Research Station, Kafr El-Sheikh, Egypt during the two successive seasons, 2011 and 2012. The results revealed that Karshensky 2, Giza 70 and Alexandria 4 were the most susceptible genotypes to infestation of green bolls by P. gossypiella and E. insulana, while Pima S 6 X G.89 was the most resistant one to both insects. On the other hand, Giza 92, Bahteem 101, Giza 86, Seuvin and Pima S 6 X G.89 were significantly resistant genotypes to infestation of green bolls by H. armigera during 2011 and 2012 seasons. A negative relationship between concentration of gossypol and ratio of infestation by insects was observed, this means the importance of gossypol concentration for reduction of the infestation by insects.
