Powdery mildews are important plant pathogens worldwide, often warranting chemical control measures. Effects on non-target organisms and resistance concerns have recently prompted the consideration of biological control. A cosmopolitan coccinellid tribe (Psylloborini) is composed of obligate consumers of powdery mildew. A western North American species, Psyllobora vigintimaculata, is being evaluated for its ability to consume spores and hyphae of mildews in greenhouses, in an attempt at augmentative biological control. A predictive exponential consumption model has been created utilizing known biological attributes of the insect, a modified Leslie matrix, a previous individual larval consumption model and data from a feeding efficacy trial conducted in the greenhouse. The model has then been employed to simulate the population growth and subsequent removal of visible mildew colonies by the insects in a controlled horticultural system. When compared against real data from the efficacy trial, the model underestimates consumption, especially in the early time-periods. The model’s limitations and assumptions are discussed, as well as the possibility of using such a model as a calculator to determine the insect release-rate necessary to bring about control in a system with known parameters.