The influence of leaf hairs of Gerbera jamesonii on the searching behaviour of the predatory mite Phytoseiulus persimilis

Some natural enemies of herbivores are hampered by leaf hairs during their search for prey or hosts. In this study it was determined whether the predatory mite Phytoseiulus persimilis is hampered by leaf hairs of gerbera (Gerbera jamesonii) while searching for its prey, the spider mite Tetranychus urticae. Three parameters of the predator's searching behaviour were quantified: walking speed, walking activity and encounter time with prey eggs. The results show that the walking speed and walking activity decreased when the hair density increased. The time needed by the predator to find its first prey item (encounter time) increased when the hair density increased. Finally the effect of leaf hair density on predation rate was studied. Predation rate was negatively influenced by leaf hairs at low prey egg densities (1.3 and 2.5 eggs/cm(2)). At 8.0 prey eggs/cm(2), predation rate was not affected by leaf hair density. At this prey density rate of encounter between predator and prey does not appear to be the factor limiting predation rate.