Nostoc, sometimes known as star jelly or witch’s butter, among other names, is a genus of cyanobacteria or blue green algae that can proliferate in almost any environment. It can infiltrate and colonize almost any ecosystem, including polar, tropical, aquatic, terrestrial environments, and more.
Colonies of nostoc are made of long filamentous chains, or strands of cells that continue to elongate without separating and can form both microscopic groups under the soil as well as visible mats on a surface. These colony mats can desiccate completely in dry conditions. Dry nostoc can easily be blown around in the wind and spread to undesirable locations. When moisture returns, colonies swell back up into dark green, gelatinous blobs. This form can be introduced to new environments on poorly sanitized tools, shoes, and clothes, or by transferring infected plants or growth media between locations. For these reasons, it is incredibly difficult to control the spread and movement of nostoc colonies inside a greenhouse setting.
Nostoc can be found growing in many different habitats including lawns, garden beds, athletic fields, paved surfaces, container nurseries, and greenhouses. They can survive in dry conditions, but for long-term survival they require a wet environment. Hard surfaces like the concrete in a greenhouse or compacted ground of a nursery are perfect environments because the frequent irrigation stands in pools on the poorly drained ground. Greenhouses provide perfect conditions for its fast growth and production of biomass due to high humidity, high temperatures, and high light levels in addition to frequent irrigation.
Phosphorous is the most limiting nutrient for nostoc, so environments high in phosphorous allow it to thrive.
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While nostoc can have symbiotic relationships with some organisms, there is still potential for competition between organisms sharing the same resources. Although it is true that nostoc contributes to nutrients in the soil, it is also responsible for using those resources to increase its own presence. The possible overgrowth of nostoc threatens greenhouses and nursery production due to competition for light and moisture as well, depending on the specific morphology of the plant in relation to the growth of nostoc. Contamination of greenhouses and nurseries can also create large areas of very slippery biomass that poses a safety hazard for growers, greenhouse/nursery workers and clientele at the site. Nostoc contamination can also be aesthetically displeasing. For greenhouses or other nursery sites sell ornamental or other agricultural plants, a heavy nostoc infestation has the potential to cause a large financial loss.
Learn more in this original post from Michigan State University. For management advice, click here to learn more.