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The spiralling whitefly Aleurodicus dispersus Russell was introduced to Africa and Asia during the 1990s. Among its potential biological control agents is the predatory coccinellid, Nephaspis bicolor Gordon. Since the coccinellid may be required to control A. dispersus under variable climatic conditions, four temperature (20-34°C) and two RH (78% and 90%) (55% RH at 26°C only) regimes were evaluated under laboratory conditions in Trinidad and Tobago. Temperature (but not RH) had significant effects on the development rate of all stages of N. bicolor and on the pupal and adult sizes. Interactions between temperature and RH were significant only for egg incubation and total duration and for size of the pupa. Mortality during development was highest at 30°C/90% RH and lowest at 23°C/78% RH. Both temperature and RH significantly affected the preoviposition period, while temperature alone affected longevity and lifetime fecundity. Adult survival at 26°C and 55% RH as well as 90% RH was significantly higher compared to all the other treatments. Based on the life table statistics, the best performance of female N. bicolor was at 26°C and 55% RH. Although feeding, survival, development and reproduction occurred under all the temperature and RH regimes, constant low and high temperatures were not conducive to the coccinellid since the survival of immature stages and adults was greatly reduced. Thus, the introduction of N. bicolor into such environments may not result in long-term establishment. It may be necessary to ‘thermally adapt’ the beetles prior to release and/or to time the field releases to coincide with favourable environmental conditions. Another solution may lie in maintaining laboratory cultures of N. bicolor and making periodic (inoculative/augmentative) releases.


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