Of mites and movement:: the effects of plant connectedness and temperature on movement of Phytoseiulus persimilis

Simulation modelling studies on the biological control of Tetranychus urticae Koch in ornamental crops suggest that the dispersal of the predatory mite Phytoseiulus persimilis Athias-Henriot in the absence of food is important in determining its ability to locate sparsely distributed patches of prey (Skirvin et al., 2002). Experimental work to examine factors influencing dispersal of P. persimilis has shown that ground substrate affects the movement of the predator, and that the greater the number of connections between adjacent plants the greater the number of mites moving. In addition, P. persimilis are able to move across as many as 10 plant-plant connections within 24 h, although the majority of predators tracked moved less than this. Temperature has a significant impact on dispersal of P. persimilis, with more mites leaving release points as temperature increases up to 25degreesC, but decreasing above this temperature. This work highlights the importance of understanding how the plant canopy and temperature influence the dispersal of predatory mites. The importance of these results for biological control in ornamental crops is discussed. (C) 2003 Elsevier Science (USA). All rights reserved.