The use of lignocellulolyticStreptomycesspp. as biological agents, to enhance thatch degradation in turf and to slow its rate of accumulation while controlling fungal growth in the thatch layer, was studied. In flask scale studies, two lignocellulolyticStreptomyces violaceusniger(= hygroscopicus) strains (YCED9 and WYE53) decomposed thatch (>30% dry weight) over a 12-week incubation period. Biodegradation was accompanied by production of extracellular cellulases, xylanases, and peroxidases. The accumulation of the polymeric, water-soluble lignin degradation intermediate acid, precipitable polymeric lignin (APPL), was also observed. Residual thatch from 12-week-old cultures had an increased lignin-to-carbohydrate ratio, an indication that although lignin was metabolized, carbohydrates were preferential carbon sources for these actinomycetes. A spore-containing soluble dry powder formulation was used as an inoculum in an in situ field experiment. This formulation was maintained in storage at 4°C for over two years without viability loss. Results from the golf green experiment showed that although treated thatch layers in established greens were not appreciably reduced over the course of one summer, theStreptomyceswere active and maintained their populations within the thatch, while fungal growth was suppressed as compared to controls. The results show that treatment of turfgrass with theseStreptomycesmay be useful for the long-term control of fungal populations within the thatch. Longer field studies are required to assess the long-term potential for also controlling thatch build-up and fungal pathogens.Key words: biocontrol, biodegradation, fungi,Streptomyces, thatch