Airborne microorganisms from bacterial and fungal species are able to act as ice nuclei and can affect sensible crops to frost such as coffee trees. Consequently, frost is one of the major problems in South-Southeastern coffee crops in Brazil. In this research, it was found three categories of organisms with ice nuclei activity (INA) in coffee leaves, basing in the mean freezing point of saline solution, around -17oC. The first category, with strong INA, it was found the Pseudomonas syringae var. garceae, a coffee tree pathogenic, as INA+. Pseudomonas syringae var. syringae behaves with soft less INA+ efficiency, comparing to the var. garceae. This last variety also causes aureolar spot disease. The second category presents a partial ice nuclei activity, including two other bacteria, Pantoea agglomerans (that is known as ice nuclei), and Corynebacterium, with mean freezing point from -7oC to -10oC. And the third category presents non-ice nuclei activity (INA-), with freezing point below -11oC, including all other bacteria and fungi. Additionally, H.vastatrix, acoffee rust disease, which already causes lots of prejudice to the crops, can be associated with an INA+ bacterium, causing frost. That result deserves a refined research, trying to elucidate how this association should be done
