THE POINSETTIA STRAIN OF THE COTTON WHITEFLY, BEMISIA-TABACI (HOMOPTERA, ALEYRODIDAE), BIOLOGICAL AND DEMOGRAPHIC PARAMETERS ON POINSETTIA (EUPHORBIA-PULCHERRIMA) IN RELATION TO TEMPERATURE

Biological characteristics of the poinsettia strain of Bemisia tabaci Gennadius were investigated on poinsettia by laboratory experiments at five temperatures (range: 16-degrees-C-28-degrees-C). In addition, the effect of rearing B. tabaci on the two plant species, Nicotiana tabacum (tobacco) (Solanaceae) and Euphorbia pulcherrima (Euphorbiaceae) (poinsettia) was investigated. The temperature-dependencies were established for the developmental time for eggs and egg-to-adult phase, juvenile mortality, adult female life-span, pre-oviposition period, age-specific fecundity, and sex-ratio. The lower temperature thresholds for egg-development, development from egg to adult and for ovipositional adults were estimated as well as the lower temperature threshold for oviposition. The thresholds were 12-degrees-C, 14-degrees-C, 8-degrees-C and 14-degrees-C, respectively. Egg-development required 126 day-degrees and the entire development into adults 327 day-degrees. Mortality was highest at 16-degrees-C, being 19.3% in the egg-stage and 95% from egg to adult. The pre-oviposition period and the adult life-span were 40 and 360 day-degrees. The age-specific fecundity of B. tabaci was described by a temperature-dependent model. The maximum daily fecundity rate was attained after 60 and 125 day-degrees for B. tabaci reared on tobacco and poinsettia, respectively. The fecundity was highest for B. tabaci reared on poinsettia. The sex-ratio was in favour of females at and above 19-degrees-C and increased with temperature. Estimates of the net reproductive rate, the intrinsic rate of increase, the finite rate of increase, the mean generation time and the doubling time were obtained. A positive linear relationship was found between r(m) and temperature, the values ranging from 0.0012 at 16-degrees-C to 0.1263 at 28-degrees-C.