Comparison of Resistance of Seven Cotton Varieties to Bemisia tabaci in Kashmar

Bemisia tabaci (Homoptera: Aleyrodidae) is one of the most important pests of cotton in Khorasan which causes crop damage and yield reductions as a result of direct feeding of plant and passing pathogenic viruses. Using resistant varieties is an economic and environmental friendly method for controlling this pest. The resistance of seven cotton varieties (Green leaf okra, Red leaf okra, Mehr, Varamin, Khordad. Sahel and Termus 14) was evaluated against B. tabaci in field experiment for the period of 2009 cropping season at Cotton Research Station East Countries of Kashmar. This study was done in a complete randomized block design with 7 treatments and 4 replications. Analysis of variance of data showed that there were significant differences among varieties in terms of pest infestation (P < 0.01). The result revealed that variety Termus 14 presented the most number of adults (2.74 per leaf), nymph (8.94 per 3.88cm2 leaf area) and egg (8.81 per 3.88cm2 leaf area) and Green leaf okra and Red leaf okra varieties presented the lowest number of adult (0.22 and 0.26 per leaf, respectively), nymph (1.16 and 1.27 per 3.88cm2 leaf area, respectively) and egg (1.34 and 1.67 per 3.88cm2 leaf area, respectively). It is suggested that more investigations should be carried out on the conventional cotton varieties, green leaf okra and red leaf okra for integrated management of B. tabaci.