PHAEOTHECA-DIMORPHOSPORA INCREASES TRICHODERMA-HARZIANUM DENSITY IN SOIL AND SUPPRESSES RED PINE DAMPING-OFF CAUSED BY CYLINDROCLADIUM-SCOPARIUM

A fungal antagonist, Phaeotheca dimorphospora, was tested for its ability to control damping-off of red pine (Pinus resinosa) caused by Cylindrocladium scoparium. In vitro, the germination of seeds coated with P. dimorphospora microconidia was significantly increased by 10% compared with uncoated seeds. In experiments carried out in Petri dishes, addition of P. dimorphospora into soil significantly reduced the population of C. scoparium and disease incidence. In the greenhouse, application of P. dimorphospora into the top layer of soil reduced pre- and post-emergence damping-off by 79.5%. Under greenhouse conditions, P. dimorphospora stimulated the population of Trichoderma harzianum, a well-known antagonist of soil-borne plant pathogens. In soil treated with P. dimorphospora, the number of propagules of T. harzianum was 100-500 times higher than in the untreated control, whereas the population of C. scoparium decreased rapidly and was not detectable 1 month after sowing.