Use of carbohydrate biostimulants as biological thatch control agents provides an attractive alternative to current thatch removal methodology, yet research on these products is limited. Our experimental objective was to characterize the effect of ‘I-MOL', a molasses-based carbohydrate biostimulant, on microbial decomposition of thatch. Cores (19 x 11 cm diam.) were sampled from a sand-based creeping bentgrass putting green (SBPG) or a clayey creeping bentgrass/annual bluegrass fairway (CF) for use in respective 6-7 or 5 wk laboratory incubation studies. In both studies, treatments included I-MOL (0.95 mL m^-2) and a carbonless I-MOL nutrient analog (zeroC I-MOL). In the study using SBPG plugs, the third treatment was a combination of the fungicide chlorothalonil (0.55 g m^-2) and I-MOL (0.95 mL m^-2). In the study using CF plugs, I-MOL and zeroC I-MOL treatments were made in combination with chlorothalonil, the third treatment was chlorothalonil and a double rate of I-MOL (1.9 mL m^-2). Both studies were run in triplicate, with treated plugs incubated in air-tight flow cells ventilated with CO₂ free air. Air efflux from each cell bubbled through respective CO₂ traps of 0.0625M NaOH solution. Electrical conductivity of NaOH solutions was recorded twice daily, and decreased linearly with trapped CO₂. Treatments were reapplied, trap CO₂ concentrations were confirmed by titration, and new NaOH solutions were prepared weekly. Fiber analyses were performed in duplicate on untreated and incubated cores. Using SBPG plugs, treatment significantly affected cumulative evolved carbon (IMOL > zeroC IMOL > IMOL + Chlorothalonil) yet fiber analyses show no trends of differential organic matter decomposition. Treatment did not affect cumulative carbon evolution in CF plugs; however, fiber analyses show a significant decrease in lignin and cellulosic fractions of I-MOL treated plugs versus others. Results of this study are inconclusive, warranting additional investigations on the efficacy of biological thatch control agents.