A SIMULATION-MODEL FOR PREDICTING THE EFF ICIENCY OF BIOLOGICAL-CONTROL OF SPIDER-MITES BY PHYTOSEIID PREDATORS .1. THE MODEL

We developed a computer simulation model predicting the efficiency of Phytoseiulus persimilis ATHIASHENRIOT as a biological control ag ent o f Tetranychus urticae KOCH. This model consisted of two main sets of 1 7 stare variables, one for the predator and the other for the prey. Th e changes of these variables were calculated by difference equations u sing various rare variables which had appeared in the reports of many authors. Two particular components in the present model were a dispers al (or cannibalism) rate of the predator depending upon female prey de nsity and a coefficient which decreases predation rate depending upon the features of the plant. These were thought to be important to predi ct actual stale of biological control by computer simulation and shoul d be evaluated by experimental and simulation studies in the future.