Ice-nucleating and dew-condensing bacteria of the genera Pseudomonas and Xanthomonas have been isolated from small grain cereals in North Africa and in the Western U.S. In Montana, we have obtained ice-nucleation-active pseudomonads from plant surfaces, sprinkler-irrigation aerosols, and from rain clouds 1500 m above wheat and barley fields. Based upon these observations, we have proposed a ... [Show full abstract] dissemination model wherein the ice- and dew-condensing bacteria that live as epiphytes on plant leaf surfaces are swept into the atmosphere and are responsible for downwind nucleation of rainfall. Overgrazing with domestic animals or other human-mediated destruction of plants and their epiphytic microflora would reduce downwind nucleation of precipitation and increase the desertification process as it is now occurring in Africa. We are searching for adapted plants to fit particular ecosystems that will support populations of efficient ice-and-dew-nucleating bacteria. A self-perpetuating bio-cloud seeding system that increases precipitation is our goal.