EFFECT OF SEEDBED STEAMING ON CYLINDROCLADIUM-FLORIDANUM, SOIL MICROBES AND THE DEVELOPMENT OF WHITE-PINE SEEDLINGS

The Egedal(R) bed steamer produced sufficient heat to kill microsclero tia of Cylindrocladium floridanum at 5 and 10 cm soil depths in one ba reroot forest seedling nursery. At a second nursery the buried inoculu m was killed only to a depth of 5 cm. Soil steaming did not affect the microsclerotia at 15 cm. The steaming reduced populations of fluoresc ent pseudomonads to undetectable levels to a depth of 20 cm and popula tions of Trichoderma species were significantly reduced in the upper 1 0 cm of the seedbed. Density of white pine seedlings sown in the steam ed beds was significantly higher (P = 0.05), and height, root collar d iameter, shoot weight and root weight were significantly greater (P = 0.05) 4 months after steaming than that of control seedlings sown in u nsteamed beds.