How to Identify and Manage Nostoc in Nurseries and Greenhouses – Part 2

Part 1 of this article series focused on the biology and identification of nostoc in container nursery and greenhouse ornamental production. Nostoc is a genus of cyanobacteria or blue green algae that can proliferate in almost any environment. Colonies of nostoc are made of long filamentous chains, or strands of cells that continue to elongate without separating and can go on to form visible mats on the surface (Photo 1). Nostoc can be a helpful organism in some situations when looking at nutrient levels and soil moisture content. Although it is true that nostoc contributes nutrients to the soil, it is also responsible for using those resources to increase its own presence. The possible overgrowth of nostoc can also lead to competition for light and moisture as well in greenhouses and nursery production sites, depending on the specific morphology of the plant in relation to the growth of nostoc. Contamination of greenhouses and nursery floors can also create large areas of very slippery biomass that pose a safety hazard for growers, workers and, potentially, clientele.

For greenhouses or other nursery sites that sell ornamental or agricultural plants for which aesthetics affect the use or sale of the product, a heavily nostoc colonized crop of plants can result from significant financial loss. Hence in this second part, we will be discussing the management strategies of nostoc.

Managing nostoc with chemical methods Pelargonic acid (Scythe) has been shown to be extremely effective at killing nostoc colonies and preventing their regrowth for three to seven weeks after application. However, this is a broad-spectrum herbicide that is highly toxic to nursery and greenhouse crops, so it should be used very carefully, according to “The continuing battle against nasty Nostoc” by Jennifer Parke. Studies at the University of Florida have found that certain chemicals are more or less effective depending on the surface nostoc is growing on. Hydrogen peroxide plus peroxyacetic acid (i.e., Zerotol 2.0) was more effective at controlling nostoc on gravel and pelargonic acid (i.e., Scythe) was more effective on plastic, while sodium carbonate peroxyhydrate (i.e., TerraCyte PRO) and generic bleach were effective on both.

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Photo Credit: gettyimages-eugenesergeev