Technical Abstract: Limited research to date has addressed how plant responses to rising atmospheric carbon dioxide (CO2) will affect their diseases despite the billions of dollars in yield lost each year. We exposed loblolly pine seedlings to ambient and twice ambient levels of atmospheric CO2 prior to inoculation with the fusiform rust fungus (Cronartium quercuum f.sp. fusiforme, CQF) or the pitch canker fungus (Fusarium subglutinans, FS). Additionally, red oak seedlings (an alternate host of CQF) were exposed to ambient or elevated levels of atmospheric CO2 prior to inoculation with CQF. In all cases, disease incidence (percent of plants infected) and disease severity (proportion of each plant affected) were determined; the latent period (time to sporulation) was also monitored for the red oak seedlings. In general, disease incidence was decreased by exposure to elevated CO2. This exposure also increased the latent period for CQF on red oak seedlings. In no instance did exposure to elevated CO2 affect disease severity. This research demonstrated that plants may benefit from exposure to the increasing concentration of CO2 in the Earth’s atmosphere through decreases in fungal disease incidence.