Liverworts (Marchantia sp.) are difficult to manage during the production of perennial environmental horticulture crops grown in containers. Liverworts are among the most serious weeds of container grown ornamentals. During the 2004 and 2009 IR-4 Environmental Horticulture Workshops, a project was prioritized to screen for products to manage post-emergent liverwort in container grown ornamentals grown primarily under cover in greenhouses or hoop houses, use sites with very few registered herbicides. Since then, liverwort has been selected as a regional research priority. Between 1976 and 2021, IR-4 sponsored 302 research trials on 37 products or product formulations with 29 actives to manage liverwort. Most research was conducted with post-emergent applications, but active ingredients typically known for pre-emergent activity were included in some post-emergent experiments along with three experiments designed to screen for pre-emergent liverwort management.
The most effective options across these studies include Avenger Ag, baking soda, Byrophyter, Racer, Scythe, SureGuard, Tower (pre-emergent), V-10233, and WeedPharm. However, Marengo when applied pre-emergently when no liverworts were initially present did provide excellent prevention. Ronstar, Neudorff’s Granular Moss Killer, Terracyte and Xeroton had variable efficacy as post emergent applications, but many of these contact products may need more frequent applications for optimal efficacy. The results from this project have successfully identified several options for pre and postemergent control of liverwort.