Whole bean leaves were dipped in a range of deltamethrin concentrations to
identify a concentration which causes no mortality, but which affected the feeding of
the predatory mite, Amb/yseius fal/acis on the eggs of the two spotted spider mite,
Tetranychus urticae. This concentration (0.0002%) was then used to assay the
sublethal effects of deltamethrin on the oviposition of the two mites, prey
consumption by the predator, and on the activity of T. urticae and A. fal/acis. The deltamethrin deposit reduced oviposition in both predator and the prey,
this egg consumption by A. fal/acis was effectively reduced by presence of chemical
on the leaf surfaces. Predators placed on leaves with no prey very quickly moved to infested
leaves and remained there as long as adequate prey was available. During a seven
days period, prey mites did not move from the leaf on which they were placed. The
predator moved to treated leaves carrying prey, but preferred untreated leaves these
were available. T. urticae activity showed that there was a significantly higher
percentage of movement on treated discs and there was also a significantly longer
average movement duration. On chemically treated surfaces, A. fal/acis showed decreased feeding and
oviposition capacity compared with the control. A. fal/acis showed no significant
increase in duration of movement on treated surfaces but the frequency of movement
was increased about 50% and the proportion of time spent in moving was roughly
doubled compared with control.