Apples are a globally important fruit crop and represent a significant portion of our Canadian fruit industry. A serious production challenge faced by the apple industry is apple replant disease (ARD). ARD is a long-standing barrier to apple productivity that affects every apple-growing region in the world. This disease has become a greater problem for growers with orchard intensification using size controlling rootstocks, resulting in higher disease pressure and more frequent replanting. Many factors cause ARD, though the primary causes are biotic, including complexes of fungi, oomycetes, and bacteria. These complexes can delay fruit-bearing by several years, and cause significant growth delays and tree mortality. Old methods for overcoming ARD are agriculturally impractical and economically costly, such as planting in virgin soil or retiring land from orchard production for several years. The impacts of chemical fumigants on environmental and human health factors have resulted in product bans that have further reduced treatment options for ARD. Many Canadian grower and agricultural institutions, including Agriculture and Agri-Food Canada, and the Ontario Apple Growers, have described the need for effective alternative approaches to ARD. This thesis comprises a discussion of approaches to ARD treatment as well as original research evaluating alternative treatments. This research was comprised of a 3-year field experiment across three orchards, and two 3-month greenhouse experiments. The orchard trials evaluated the effectiveness of plant growth-promoting microbial biocontrols to alter soil rhizosphere microbial communities and reduce disease effects. This research concluded that plant growth promoting(PGP)-rhizobacteria were as effective as chloropicrin chemical fumigation in improving replant outcomes and tree growth. As well, the experimental data indicated that no specific soil microbe drove ARD at the Simcoe Research Station. The greenhouse experiments evaluated rootstock genotype tolerance to ARD. This research found that G.214, B.10, G.890, and G.935 showed the greatest ARD tolerance of 10 commercially available rootstocks. These rootstocks did not support lower pathogen populations but were less impacted by their presence. This research lays important groundwork for the development of practical protocols to inform growers on how to approach sustainable and successful replant events.