Comparative histopathology of the chitin synthesis inhibitors nikkomycin X/Z, nikkomycin Z and polyoxin D. I. Effects on moulting, reproduction and digestion in the spider mite Tetranychus urticae

The effects of the closely related chitin synthesis inhibitors, the nucleoside peptidyl antibiotics nikkomycin X/Z, nikkomycin Z and polyoxin D on the two‐spotted spider mite, Tetranychus urticae, have been studied by electron microscopy. The application of all three compounds, nikkomycin X/Z (95% active ingredient, ratio of components unknown), nikkomycin Z (pure component) and polyoxin D (pure component) disrupted cuticle, eggshell and yolk synthesis and influenced the silk and salivary glands. Ultrahistological patterns indicated differences in the mode of action of the three compounds which were especially evident in an alteration of the nuclear ultrastructure in the mid‐gut cells, which was only caused by polyoxin D. Mechanisms of action and their consequences on function, based on previously published information on the action of these compounds, are discussed.