The greenhouse thrips (Heliothrips haemorrhoidalis) is a serious pest of fruits and ornamental plants. In the Morris Arboretum’s greenhouse complex, this thrip has been prevalent, and could cause major damage to the young plants that are being propagated. The purpose of this project was to search for a suitable biological control of the thrips since chemicals have only been marginally effective. A predatory spider mite (Amblyseius cucumeris) and minute pirate bugs (Orius insidiousus) were chosen for the study. The results suggest that the minute pirate bugs are highly effective at hunting thrips, while the spider mites had no measurable effect.