Development, longevity and fecundity of Bemisia tabaci (GENN.)
Firas Al-Zyoud and Cetin Sengonca
The cotton whitefly, Bemisia tabaci (Genn.) (Hom., Aleyrodidae), formerly being confined to tropical and subtropical regions
of the world (Cock 1993), has since the late 1980’s become increasingly important as a pest of greenhouse crops in temperate regions world-wide (Broadbent et al. 1989). In Germany, this pest was recorded for the first time in 1987 on many cultivated ornamental plants (Burghause 1987). Nowadays it has spread to many greenhouse ornamentals but to few vegetable fields (Albert 1990).
There are many factors that influence B. tabaci biology, among them temperature and host plant species (Powell & Bellows 1992a). It shows great variation in developmental rates on different host plants (Coudriet et al. 1985) and at different temperatures (Butler et al. 1983). However, detailed knowledge on this pest was insufficient in the literature under low temperatures.
Therefore, the present work was aimed to study possible influence of host plant species and temperature on B. tabaci development, longevity and fecundity under controlled laboratory conditions. Such basic information was essential for a better understanding of the biology of B. tabaci and for the development of management strategies to successfully combat infestations of the insect in temperate greenhouses.
The results showed that there were four immature instars of B. tabaci on all the host plants at the two temperatures (Tab. 1). There were some significant differences in the mean developmental duration within the same stage and temperature among the different plants. B. tabaci developed significantly faster on tomato, tobacco and cucumber than on sweet pepper and cotton at 18°C, while at 30°C it developed significantly faster on cotton and slower on tobacco than on the other plants.
Mean longevity of B. tabaci was at 18°C significantly longer on cotton with 24.75 days for && and cucumber with 19.25 days for %% than on the other plants. At 30°C it was significantly longer on cucumber with 11.7 days and shorter on tobacco with 7.5 days for && as well as longer on sweet pepper with 8.55 days and shorter on tomato with 5.65 days for %% (Fig. 1). There were some significant differences in the mean longevity between the different sexes within the same host plant and temperature.
An increase in temperature from 18°C to 30°C resulted in increased fecundity of B. tabaci (Fig. 2). Mean total number of laid eggs/& was significantly higher at 30°C than 18°C on all the host plants. At 18°C it was significantly higher on cucumber with 47.1 and cotton with 46.3 than on the other plants, while at 30°C it was significantly higher on tobacco with 98.1 and lower on sweet pepper with 39.3
