Greenhouse evaluation of Trichoderma harzianum for the control of Sclerotinia wilt (Sclerotinia sclerotiorum) of sunflower

Sclerotinia sclerotiorum, the causal organism of Sclerotinia wilt, is an economically important disease affecting sunflower in South Africa. The goal of this investigation was to evaluate the potential of a strain of Trichoderma harzianum, T77, for control of S. sclerotiorum on sunflower under in vitro and greenhouse conditions. In vitro dual culture bioassays and ultrastructural studies revealed that mycoparasitism is the probable primary mode of action as initial signs of hyphae of T. harzianum coiling around hyphae of S. sclerotiorum were observed. Under greenhouse conditions, treatment of severed stems with T77 significantly reduced sclerotia formation but not the rate of disease progression. This study indicates the potential of T. harzianum in reducing sclerotia formation in sunflower and warrants further investigation.