Identification and biology of two whitefly species on cassava in Sri Lanka

Abstract

A survey in four distant locations: Anuradhapura, Madampe, Sri Jayewardenapura and Uda Walawe of Sri Lanka to identify the whitefly species related to cassava revealed two species, namely Bemisia tabaci (Gennadius) and Alerodicus dispersus (Russell). The species B. tabaci was recorded in all four surveyed locations, while A. dispersus was collected only from the first three locations. The results of the study on the pest life cycle under the laboratory conditions showed that, B. tabaci and A. dispersus passed through four nymphal instars before the adult stage. The mean duration values of these stages were 7.2, 7.5, 4.7, 5.6 and 8.5, 6, 9, 9 days respectively for the two species. The total duration of the life cycle of B. tabaci ranged from 22-57 days at the temperature of 29±2°C with a mean of 37.5 while that of A. dispersus was 27-68 days with a mean of 48 respectively (at 28±2°C).The damage to crop plants caused by two whitefly species is discussed with a special emphasis on their ability to transmit viral diseases.