Ecological stoichiometry can help clarify how symbionts and other co-occurring organisms mediate nutrient deficiencies for hosts. We used ecological stoichiometry (comparisons of elemental compositions in food vs consumer) to investigate whether obligate mutualist fungi (Grosmannia clavigera, Ophiostoma montium) of the tree-killing bark beetle Dendroctonus ponderosae (mountain pine beetle) and the invasive tree pathogenic fungus, Cronartium ribicola (causal agent of the disease white pine blister rust) influenced availability of carbon, nitrogen, and phosphorus to the beetle in Pinus albicaulis (whitebark pine), as well as how these elements varied among three populations of the tree.