Effect of temperature, moisture, soil type and Trichoderma species on the

The survival of Fusarium pseudograminearum (Fp) in wheat straw was reduced significantly (P<0.05) when the straw was sprayed with spores of isolate BM1 of Trichoderma koningii (Tk), incorporated into an acid red duplex soil and incubated for 4 months at two temperatures (15°C and 25°C) and at three water potentials (−0.03 MPa. −0.3 MPa and < −50 MPa). The greater reduction of the pathogen in the moist soil (−0.3 MPa) compared with the wet soil (−0.03 MPa) at both temperatures was associated with greater colonisation of the straw by Tk. After 6 months at 25°C in the moist soil, the pathogen was completely eliminated from the straw pieces and replaced by Tk. In air-dry soil (< −50 MPa), Fp survived in 100% of the straw pieces even after 6 months at either temperature. When infested straw was sprayed with seven antagonistic isolates of Trichoderma spp. and incorporated into either an alkaline black earth or an acid red duplex soil, the survival of the pathogen was generally greater in the alkaline black earth. However, another Tk isolate (TW3) and a T. harzianum (Th) isolate (TW7) reduced the survival of the pathogen to low levels (3–30%) after 3 months at 30°C in both soils. The results suggest that it may be possible, at least in the summer-dominant rainfall wheat are as of Australia, for Trichoderma species to reduce substantially the inoculum of Fp during the 6-month fallow period.