A rapid and reliable in vitro bioassay method to test the effects of synthetic and natural compounds on the development of greenhouse whitefly Trialeurodes vaporariorum Westwood (Homoptera Aleyrodidae) is described. Leaf fragments of Nicotiana glauca Graham infested with eggs of whitefly were cultured under aseptic conditions on half‐strength Murashige‐Skoog medium. The development of the insect in vitro and in vivo were comparable except for a higher mortality rate in the first larval instar. Ecdysteroids from Ajuga reptans L. were applied to leaf fragments by immersion in aqueous solution of the compounds or by addition to the culture medium. A high mortality rate of first larval instars was detected with 29‐norsengosterone and ajugalactone treatments. This effect was specially pronounced when the products were incorporated in the medium. A significant increase in mortality was also recorded in the pupal state with a 20‐hydroxyecdysone treatment. This effect was never observed before, because all whitefly larvae on A. reptans leaves die in the first larval instar.
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Melé et al. (1992) studied this question.