Because of current concerns regarding the release of genetically engineered microorganisms (GEMs) into the environment, the fate, survival, and effects of many GEMs will need to be evaluated in small-scale releases performed in controlled, contained environments. In the study, the use of greenhouses for predicting the results of field releases, and the influence of bacterial genus, plant genus and environmental conditions on bacterial survival in the greenhouse and the field were investigated. Erwinia herbicola, Pseudomonas syringae, and Klebsiella planticola were sprayed on oat plants (Avena sativa) and bean plants (Phaseolus vulgaris) in one greenhouse experiment and in two field experiments. Plants were sampled, and 21 days after bacteria were applied and temperature, relative humidity, and incident light were recorded per minute and averaged per hour. Despite the application of equivalent bacterial concentrations in the experiments, bacterial populations after only one day post-application were significantly lower in the field experiments as compared to the greenhouse experiment.