An isolate ofTrichoderma harzianum(IMI no. 238493) directly attacked and lysed the mycelium and sclerotia ofSclerotium rolfsiiwhen the two fungi were grown in dual culture. The type of interactions between the antagonist and pathogen were hyphal coiling, entry through haustoria‐like structure and direct entry in the hyphae and sclerotia ofS. rolfsii, the host fungus. In a glasshouse experiment,T. harzianumapplied in the form of sorghum culture to 5.rolfsiiinfested soil gave as high as 76 and 88% disease control in first and second growth cycle of sugarbeet seedlings respectively. The degree of disease control obtained increased with the increase in the amount ofT. harzianumapplied. This isolate ofT. harzianumwas found tolerant to PCNB (Pentachloronitrobenzene)in vitro.PCNB at low concentration when integrated withT. harzianumimproved disease control. Under field conditions, integration of PCNB andT. harzianumsignificantly reduced the incidence of Sclerotium root rot (76% disease control) and increased the root, green foliage and sucrose yield per ha.