| Abstract: | The seasonal fluctuation in the production of coremia by Ceratocystis ulmi (Buis.) was studied on elm stem discs taken from trees felled in April, June, July, September, October and November 1971 at Valcartier, Quebec. More coremia formed on stem discs of trees felled during the growing season. Except for trees felled in October and November, more coremia formed on sapwood than on heartwood. Evidence obtained during the study showed that the compounds, which trigger coremia formation, are not uniformly distributed within and between trees or throughout the period from April to November. |
