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 abil ity to control damping-off of red pine (Pinus resinosa) caused by Cyli ndrocladium scoparium. In vitro, the germination of seeds coated with P. dimorphospora microconidia was significantly increased by 10% compa red with uncoated seeds. In experiments carried out in Petri dishes, a ddition of P. dimorphospora into soil significantly reduced the popula tion of C. scoparium and disease incidence. In the greenhouse, applica tion of P. dimorphospora into the top layer of soil reduced pre- and p ost-emergence damping-off by 79.5%. Under greenhouse conditions, P. di morphospora 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 s owing.