Airborne microorganisms from bacterial and fungal species are able toact as ice nuclei and can affect sensible crops to frost such as coffee trees.Consequently, frost is one of the major problems in South-Southeasterncoffee crops in Brazil. In this research, it was found three categories oforganisms with ice nuclei activity (INA) in coffee leaves, basing in themean freezing point of saline solution, around -17oC. The first category,with strong INA, it was found the Pseudomonas syringae var. garceae, acoffee tree pathogenic, as INA+. Pseudomonas syringae var. syringaebehaves with soft less INA+ efficiency, comparing to the var. garceae.This last variety also causes aureolar spot disease. The second categorypresents a partial ice nuclei activity, including two other bacteria, Pantoeaagglomerans (that is known as ice nuclei), and Corynebacterium, withmean freezing point from -7oC to -10oC. And the third category presentsnon-ice nuclei activity (INA-), with freezing point below -11oC, includingall other bacteria and fungi. Additionally, H.vastatrix, acoffee rust disease,which already causes lots of prejudice to the crops, can be associatedwith an INA+ bacterium, causing frost. That result deserves a refinedresearch, trying to elucidate how this association should be done.74UFSM, 33 (2)Therefore, two rust coffee diseases and aureole spot, as well as the presenceof Pantoea agglomerans, can be directly or indirectly associated to icenuclei activity, demanding a higher bio-control, particularly duringwintertime, due the possibility of frost damage
