This paper uses a methodology based in fuzzy sets theory in order to describe the interaction between the prey, Aphis glycines (Hemiptera: Aphididae) the soybean aphid, and its predator, Orius insidiosus (Hemiptera: Anthocoridae) and to propose a chemical control for soybean aphid. Economic thresholds were already developed for this pest. The model includes biotic (predator) and abiotic (temperature) factors, which affect the soybean aphid population dynamics. This model is very useful to predict timing and releasing numbers of predators for soybean aphid biological control Ver menos