The coccinellid tribe Psylloborini (Halyziini) is entirely comprised of obligate consumers of powdery mildew (PM) fungi (Ascomycota: Erysiphales). The small ashy gray ladybird beetle, Psyllobora vigintimaculata Say, a North American species, is being evaluated for use as a biological control agent against PM in greenhouse systems. A simple model based on laboratory data predicts that an individual larva cleans 6.3 ± 3.3cm² leaf area of all visible PM hyphae and conidia from the time of egg eclosion until pupation. Additionally, PM removal efficacy trials on plants of known leaf area in greenhouse cages were used to track PM severity over time when exposed to several initial release rates of adult beetles. These figures were incorporated into a dynamic population model for both the insect and its PM food source in a simulated greenhouse environment. When crop leaf area and PM severity can be estimated this model can be viewed as a release rate calculator that predicts the number of adult female beetles to release in order to gain PM control in a specified time frame.