Armillaria root disease (caused by Armillaria mexicana and/or A. mellea) causes peach (Prunus persica) mortality in orchards of the Mexican sub-tropics. Three Prunus rootstocks were evaluated for resistance/susceptibility reactions to A. mexicana and A. mellea under greenhouse and field conditions. In the greenhouse, A. mexicana and A. mellea were independently inoculated on 21 trees for each of three rootstocks: P. persica × P. davidiana ‘Nemaguard’, P. persica landrace ‘Criollos of La Goleta’ genotypes, and P. salicina Japanese plum ‘Mondragon’, each with four non-inoculated trees as controls. After greenhouse inoculations with A. mexicana, ‘Mondragon’ showed the lowest (2.5%) incidence of infected roots, while ‘Criollos of La Goleta’ and ‘Nemaguard’ rootstocks showed the highest (21.6% and 24.6%, respectively). Root dry weights, root volumes, and plant dry weights were greater (2.2-4.8 X higher) in the ‘Criollos of La Goleta’; however, abundant mycelial infections were observed in the root systems. Greenhouse inoculations with A. mellea resulted in lower (17.5%) incidence of root infection. In a commercial orchard infested with A. mexicana, 21 plants of ‘Mondragon’ (cutting-derived), ‘Criollos of La Goleta’, and P. mume ‘Japanese apricot’ were inoculated with A. mexicana. ‘Mondragon’ showed the lowest susceptibility to A. mexicana. Identifying A. mexicana-resistant ‘Mondragon’ rootstock is key for management of Armillaria root disease in peach orchards of Mexico.