Abstract
Using autoradiography it was shown that saliva of T. urticae injected into the plant was transported to the growing regions. Indications were found that the two-spotted spider mite has an active phosphate metabolism. A local mite infestation on a bean pla~t caused an increased transport of phosphates to the top leaves and the roots. At the same time an increase of P transport towards the infested leaf was ascertained. It appeared that this was not caused by a wound reaction but by a physiological influence of the mites via their saliva secretion into the host plant. A mite population in bean interferes with the equilibrium of the growth promoting substances present in the plant. Under certain conditions a slight infestation of mites (1--4 ~ per crn 2) causes a growth stimulation. A heavier infestation (more than 10 ~ per cm ~) causes growth inhibition. Using thin layer chromatography an indole compound was found in the mites. In bean plants infested with mites the amount of gibberellin appeared to be markedly increased.
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