Abstract: Aculops lycopersici is a key pest on tomato on a worldwide scale, causing severedamages in protected crops. The difficulty in controlling this pest with synthetic pesticides hasenhanced the interest in biological control agents. Transeius montdorensis was reported as apromising predator. In this study, preventive strategies have been evaluated based onintroductions of the predator combined with releases of astigmatid mites as complementaryfood. A trial on potted tomato plants placed in a climatic chamber showed that the pest did notdevelop after release on the plants where the predator had been established. Success wasobtained in all three evaluated treatments, with different timing and ratios of releases. Two ofthese strategies were tested in a greenhouse in walk-in cages. After artificial infestation,successful control was also obtained as long as the climate conditions allowed to keep highpredator populations. A program of releases was then evaluated in a greenhouse. Naturalinfestation of the tomato plants with the pest occurred in all the control plots without predators,where severe damage occurred. The plots with predators were only colonized by the pest whenhigh populations had already developed in the control plots.