Preliminary Field Plot Trials on Biological Control of Sclerotinia trifoliorum by Coniothyrium minitans

Abstract

SUMMARYLaboratory‐cultured sclerotia of Sclerotinia trifoliorum were placed in retrievable nylon bags on the surface of initially bare field plots and treated with three levels of a pycnidial dust preparation of the parasitic fungus Coniothyrium minitans. Four trials were set up, two beginning in July 1972 and two on 28 February 1973; each ran for 12 weeks. After that period in the first July trial, 37, 53 and 65 per cent destructive infection of sclerotia and 88, 93 and 98 per cent total infection of sclerotia (destructive and slight infection) occurred at the increasing levels of applied inoculum. In the second July trial there was much less infection, attributed to less weed growth in the plots and consequent lower surface moisture. Both the early spring trials resulted in appreciable infection of sclerotia. This was less than in the first July trial but greater than in the second, and was interpreted to be a result of a combination of lower temperatures and satisfactory moisture conditions.