Small is superior: Plant-provided prey refuges, predator-prey dynamics and biological control

Herbivorous prey are known to employ various strategies to avoid predation. In this thesis, I investigated interactions of eriophyid mites, important agricultural pests, which hide inside refuges, where they are temporarily safe, and their natural enemies. I found that only a smaller member of the predatory mite guild on coconut trees was able to enter refuges of the coconut mite, consisting of the area of the coconut covered by the perianths. However, they could only do so after the distance between the perianth and the coconut surface had increased with time. To further understand the role of this refuge, I experimentally increased its entrances in the field, and found that successful control of the pest critically hinged on refuge opening and predator size. I furthermore prove that this predatory mite and a larger, commercially available species responded to prey-associated volatiles, but only the smallest mite was able to move into narrow spaces such as the prey refuge. Although it has been suggested that larger predators have the advantage to easily subdue their prey, being small thus seems advantageous when prey hide inside refuges. I furthermore demonstrate that this small predator can control the dry bulb mite on Dutch tulip bulbs. These mites hide between bulb scales and cannot be reached by the conventionally used larger predatory mites. Thus, I show that a small tropical predatory mite from the tropics can be used to control an important pest of Dutch tulip bulbs.