NATURAL OCCURRENCE OF CHONDROSTEREUM-PURPUREUM IN RELATION TO ITS USEAS A BIOLOGICAL-CONTROL AGENT IN CANADIAN FORESTS

The incidence of natural fructification of Chondrostereum purpureum wa s estimated quantitatively on southern Vancouver Island during two win ter seasons in randomly located 1000-m(2) plots and compared with pote ntial added fructification that might occur as a result of using the f ungus to control stump-sprouting of hardwood weeds in young forest sta nds. Fructification was surveyed in forests as well as in urban or agr icultural areas by estimating the surface areas of woody substrates co vered with basidiocarps. In addition to random plots, estimates were m ade also in locations where the fungus would be expected to occur (woo dpiles, silvicultural thinnings, and killed trees). Basidiocarps were found throughout the area in various types of forest cover as well as in urban or agricultural situations. The amount of added fructificatio n through the use of the fungus as a biological control agent was dete rmined from inoculated plots as well as from calculated stump-surface areas developed from published stand-density data. Added fructificatio n was multiplied by a factor representing the maximum biological contr ol frequency in order to compare added fructification with natural fru ctification values. From the various calculations, it was determined t hat the added fructification of C. purpureum is of the same order of m agnitude as naturally occurring levels or even lower. In addition, the re is a distinct geographical separation between predominantly forestr y and predominantly settled areas where fruit and ornamental trees are cultivated. Accordingly, it was concluded that using the fungus as a biological control agent in forestry is not likely to pose a significa nt threat to fruit growing and commercial forests. (C) 1996 Academic P ress, Inc.