SENSITIVITY OF ROOT-ROT ANTAGONIST PHLEBIOPSIS-GIGANTEA SPORES TO HIGH-TEMPERATURE OR PRESSURE

Aqueous suspensions of Phlebiopsis gigantea oidiospores, used as a bio logical control agent against Heterobasidion annosum, were either (1) set under pressure, (2) warmed or (3) used in mechanized stump treatme nt. Survival of P. gigantea following these treatments was monitored b y estimation of oidia germination on agar medium and compared with the germination of oidia from control suspensions. Pressure up to 2200 kP a had no effect on the survival of P. gigantea. No effect on the survi val was detected following incubation at ambient pressure for between 5 min and 8 h at 20 degrees C. Phlebiopsis gigantea spore germination had an optimum at 30 degrees C. When exposed to temperatures exceeding 30 degrees C, viability of P. gigantea spores decreased with time. Du ring mechanized stump treatment, survival of P. gigantea was not signi ficantly lower. neither after the suspension had passed through the st ump treatment device nor after 7 h time, compared with a fresh control suspension. Thus, mechanized application under normal summer conditio ns in Sweden did not obstruct the spore germination of P. gigantea in this study.