Abstract
Life-history parameters (juvenile development time, adult longevity, host instar preference and rate of parasitism) of four parasitoids of Bemisia argentifolii (two strains of Encarsia formosa (D and B), Eretmocerus eremicus and Eretmocerus mundus) were studied in the laboratory. At 15°C juvenile development time was the shortest for E. formosa B (48 days), longest for E. ere- micus (79.3 days) and intermediate for E. formosa D (62.8 days) and E. mundus (64 days) at 15°C. With increase in temperature, development time decreased to around 14 days for all species/strains at 32°C. The lower developmental threshold for development was 11.5, 8.1, 13.0 and 11.5°C for E. formosa D, E. formosa B, E. eremicus and E. mundus, respectively. E. formosa D and B, and E. mundus all appeared to prefer to parasitize 3 rd instar nymphs. The presence of hosts shortened adult longevity in most of the para- sitoids, with the exception of E. formosa B, which lived longer than other species/strains irrespective of the presence of hosts. At 15°C daily parasitism was very low by all parasitoids. The two Encarsia strains had a constant, but low rate of reproduction during adult life, while the two Eretmocerus species had a very high rate of reproduction when one-day old, which then decreased very quickly. Lifetime fecundity, estimated using a non-linear model, indicated that it was higher for the two Encarsia strains than for the Eretmocerus species. Life history parameters reported in the literature for the four parasitoids are reviewed and compared with our results. Finally, the potential value for the biological control of whiteflies on greenhouse crops of parasitoids having either a high reproductive rate over a short period (Eretmocerus spp.) or a low rate of reproduction over a long period (Encarsia spp.) is discussed.
Highlights
Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) was first described in 1889 as a potential pest of tobacco in Greece (Gennadius, 1889)
At 15°C mean development time was shortest for E. formosa B, longest for E. eremicus, and intermediate for E. formosa D and E. mundus
Longer development time at 16°C (72.8) than we did at 15°C (62.8)
Summary
Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) was first described in 1889 as a potential pest of tobacco in Greece (Gennadius, 1889). It was frequently reported as a pest of field crops, like bean and cotton (Brown et al, 1995), and causing serious damage to poinsettia in greenhouses in Florida (Price, 1987). Bemisia spread all over the United States damaging a range of field crops, vegetables and ornamental plants. It was accidentally imported into Europe around 1987 (Fransen, 1994) and became a serious pest of crops in greenhouses. Bemisia causes direct feeding damage, vectors a number of devastating plant viruses, reduces the quality of the harvested product as a result of the excretion of honeydew, and can be the source of various other problems (Drost et al, 1998)
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