In the early 1800s Canada's economic base shifted from the fur trade to agriculture, reflecting the creation of agricultural societies dedicated to improvement in the quality of both product and practice. Ralph Estey chronicles the history of plant pathology and mycology in Canada from this early period to the late 1940s when it entered its professional, biochemically oriented phase.

Major topics include the pioneering roles of entomologists and horticulturalists in the genesis of plant pathology; the influence of diseases in potatoes, grain, and forage crops on early developments in plant pathology and mycology; the factors prompting the development of the relatively new sciences of forest pathology and nematology; and the teaching of plant pathology.

Estey discusses early legislation in Canada pertaining to plant diseases and the faltering first steps at international regulation, and provides a detailed history of mycology province by province.