Tuesday, November 6, 2007

Greenhouse and Nursery - Controlling Liverworts

Photo from the Biological Sciences Greenhouse Facility, The Ohio State University

Liverworts can be a problem pest in greenhouses and nurseries, especially in long term perennial production areas. The following is an article on this subject.
Liverworts, Marchantia polymorpha, are bryophytes that are green plants without roots that can establish themselves and become a persistent problem in a commercial greenhouse. Most people accidentally introduce liverworts by bringing in a crop plant with the liverwort present. Liverworts produce spores that can persist in a greenhouse for one year or longer. Once established it is very difficult to control in greenhouses. Removal of liverwort by hand is labor intensive and often damages the crop in the process. If this plant becomes established in a greenhouse all infested plants should be discarded and all floors, benches, structures and glazing should be sanitized using a disinfectant. For perennial crops in a greenhouse, an application of Ronstar or Surflan can be applied to substrate surfaces to prevent the spores from germinating. If young liverwort plants start to grow then try applications of ZeroTol (hydrogen dioxide), TerraCyte (sodium perocarbonate) or Physan 20 (quaternary ammonium chloride salt). These materials act as biocides and will burn back young liverwort plants. The sodium in the TerraCyte causes liverworts to desiccate and you can generally kill back about 70 % of the plants. The sprays are more effective against younger plants. Placing a layer of coarse pine bark or coca shell will keep the surface dry and make conditions less conducive for liverwort growth. The best advice is to keep liverwort infested plants out of your greenhouse. Once it is introduced it will be a difficult battle to get rid of this persistent pest.
Extracted from the November 30, 2006 issue of the Greenhouse TPM/IPM Weekly Report University of Maryland Cooperative Extension

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