Threshold of Development and Thermal Constant for Different Stages of the Seychelles Fluted scale, Icerya seychellarum (Westwood).

Abstract

Different biological features of Icerya seychelarum were carried out at three constant temperatures (25ºC, 30ºC and 35ºC) on mulberry seedlings, Morus alba L. throughout one complete generation. Durations and rate of development percentage for different developmental stages were estimated. Results revealed that egg incubation period, durations of nymphal stage were decreased as temperature increased from 25ºC to 35ºC. Rates of development percentage of both egg and nymphal stages were increased as temperature increased from25ºC to 35ºC. Also, results revealed that temperature had highly significant effects on durations of female pre-oviposition, oviposition and post oviposition periods. These durations were decreased as temperature increased from 25ºC to 35ºC. Hypothetical threshold (zero) of development was 12.25, 17.62. 21.9 and 21.4 days for egg, nymphal stage, pre-oviposition and oviposition periods; respectively. Mean thermal units were 86.75, 552.64, 84.58 and 204.92 degree/days for egg, nymphal stage, pre oviposition and oviposition periods; respectively. All these parameters revealed that 25ºC seemed to be optimal temperature for rearing the Seychelles fluted scale.