Nymphal Survival and Crawler Movement of Bemisia tabaci (Homoptera: Aleyrodidae) on Different Varieties of Cotton, Gossypium hirsutum

Nymphal survival and crawlers movement of Bemisia tabaci (Homoptera: Aleyrodidae) on different varieties of cotton, Gossypium hirsutum, was studied on 5 different varieties including, Varamin, Kucker-312, Bulgar-557, Sahel-80, and native (red leaf/red boll) at 24±2 °C, 65±5% RH, 16:8 (L: D) photoperiod in the greenhouse condition. Crawler's movement was significantly different on the varieties. The highest average movement was 77.93±14.62% on the Native variety, and the lowest one was 17.84±9.71% on Bulgar-557. Mean percentage of survival of the eggs on the native variety was lower than other varieties and significantly different; but it was not significantly different on other varieties and also their different leaf surfaces. Study on the immature life stages from 1st instar to pupa indicated that mean percentage of survival of different life stages was significantly different on the varieties; so that the lowest one was on Native, and the highest one was on Bulgar-557 and Sahel-80. Of the different varieties, Varamin was the only variety which the mean percentage of survival was different on adaxial and abaxial leaf surfaces, as it was determined 65.87±13.45 and 58.12±17.31 percent, respectively. Mean percentage of mortality of different life stages including, 1st to 4th nymphal instars, prepupae, and pupae was separately studied on the adaxial leaf surface of Native variety. The highest and the lowest mortality was occurred in first (between 1st and 2nd nymphal instars) and fifth (between prepupa and pupa) stadia, respectively. Movement of crawlers from abaxial to adaxial leaf surface was not dependent on leaf orientation and photoperiod; therefore, phototropism and geotropism are not effective factors for sweetpotato crawlers’ movement, while other factors especially different characteristics of abaxial and adaxial leaf surfaces have the major role in this behavior.