Two similar inclined boxes were constructed differing in several aspects from one developed earlier to regulate soil moisture potential. Each box had six 10-cm wide compartments with a perforated plastic cover. Boxes were placed in a room held at 10°C with a RH of 90%. The differential perforations in the plastic that covered the soil surface regulated evaporation which in turn regulated soil moisture. One box was used to carry out experiments on five herbicides at different matric potentials while the other box was used to test five mycoparasites. The herbicides chlorsulfuron, cyanazine, metribuzin, triallate and trifluralin significantly reduced the carpogenic germination of sclerotia of Sclerotinia sclerotiorum. Among five mycoparasites, Coniothyrium minitans completely inhibited germination. Penicillium sp., Sporidesmium sclerotivorum and Teratosperma oligocladium reduced germination in one of the two tests. The influence of soil moisture on carpogenic germination was significant in all tests. There were interactions between herbicides and moisture and also between mycoparasites and moisture. However, soil moisture did not have a marked effect on the efficacy of herbicides and mycoparasites.