The plant pathogen, Sclerotinia sclerotiorum, was further investigated as a potential bioherbicide targeting the problematic weeds Cirsium arvense (Californian thistle) and Ranunculus acris (Giant buttercup). Previous research has found that S. sclerotiorum can be effective at controlling both weeds with bioherbicide work primarily focused on solid substrate production of fungal mycelium, which has proven cost-prohibitive to scale up. The primary objective of this research was to investigate whether S. sclerotiorum could produce microsclerotia (MS) in liquid fermentation. Liquid fermentation is more cost-effective and scalable than solid substrate production. MS are small and resilient fungal propagules with characteristics such as desiccant tolerance and shelf stability, that make them attractive as propagules to be used as an active ingredient for a bioherbicide. Although MS production has been demonstrated for other species of fungi, it has not previously been reported for S. sclerotiorum. The suitability of MS incorporated into a S. sclerotiorum bioherbicide formulation was additionally assessed. Six S. sclerotiorum isolates (S36, S37, GGB1, GGB2, G57 and G64) were screened for their suitability for future bioherbicide development. The growth of the isolates was compared under a range of illumination (12 hr photoperiod or 24 hr darkness) and temperature (15 °C, 20 °C and 25 °C) conditions. Their pathogenicity on excised leaves of C. arvense (provenances G20 and G27) and R. acris (haplotypes A, A2, G and J) was compared. GGB2 was found to be the fastest growing isolate and was one of the most pathogenic isolates on both host species. This isolate is a potential candidate for future research. Seven liquid media with varying compositions were screened for their ability to induce MS formation with S. sclerotiorum isolate S36. A single media was identified that resulted in MS production, yielding 4.5 x 103 MS per mL after 14 days of fermentation at 300 rpm. Bioassays using formulations of these MS as inoculum on excised leaves of C. arvense and R. acris initially showed promising results. MS inoculum caused lesions on both species covering a large proportion of the leaf area and resulted in lesions significantly larger than those from a sclerotia inoculum (P < 0.001). Replications of the bioassay resulted in no lesions with the MS formulations, which led to further investigation of the formulation and drying process. The survival of the MS at each step of the formulation process was examined. The survival of the structures decreased dramatically when dried to below 30% moisture. Adjusting the fermentation time and carrier used did not improve MS viability after the drying step. Microscopy of the MS ultrastructure indicates that the drying process may be causing damage to the hyphal cell membranes, resulting in lysis of the cell and potentially causing low viability. Production of S. sclerotiorum MS has been demonstrated for the first time. Despite the inconsistency of MS of S. sclerotiorum to survive drying and cause infection, MS remain a promising propagule for a future bioherbicide. Optimization of the fermentation and formulation should be the focus of future work. If reliable production of desiccant tolerant MS of S. sclerotiorum can be achieved, this would present an opportunity to enable the sustainable management of C. arvense and R. acris.