Goodbye Green Slimy Things! A Study on Cleaning and Sanitizing for Nostoc Control

What is Nostoc?

Nostoc”, a green jelly-like film growing over gravel or on ground surfaces that are constantly wet, is a combination of different cyanobacteria species living together (initial observations at the NWREC Pathology Lab). Cyanobacteria are bacteria that are capable of photosynthesizing and in some species, fixing nitrogen! While seemingly innocent enough, the cyanobacteria aggregate to form vast mats, composed of a gooey, gelatinous texture when wet. 

Nurseries in particular struggle with the omnipresent Nostoc. Like all living organisms, cyanobacteria need water and nutrients to grow, and what better place to find such things than the ground of a nursery! Runoff from fertilizer and excessive irrigation only complicates the problem. There is only temporary relief if the mats dry out. But they are only resting; the cells are still very much alive. Then, as if out of a movie, the cyanobacteria slowly spring back to life and swell when water returns. Over the years, the cyanobacterial mats accumulate and continue to grow, creating a larger and larger issue. Not only are the cyanobacteria unsightly, but they pose a major slip hazard for nursery workers

What were our objectives and experimental set-up?

  • The objective of this study was to assess the efficacy of manual Nostoc removal (cleaning) on overall control of the microorganism.
  • As a secondary objective, we tested different sanitizers to determine if a couple maintenance applications after cleaning could further contribute to Nostoc control. In short, our question was “Does cleaning AND sanitizing control Nostoc presence and growth in a nursery setting?

We worked in collaboration with a local nursery on this project. The site selected was on level ground and received 6 hours of irrigation per week. The entire area had nearly 100% Nostoc coverage. Plots measuring 4’ x 3’ were established by using flagging tape and stakes. The plots were divided into three blocks of five plots each. This allowed for three replicates of the five sanitizer treatments. Each plot was then divided in half, creating two subplots. One subplot received a complete manual removal of Nostoc. This removal was simple; the cyanobacterial mats were raked using a plastic rake and then placed in trash bags. The other subplot was left as is, with complete Nostoc coverage.

What treatments were used?

After the respective subplot was cleaned, the treatments were applied to both the clean and the uncleaned sections. The treatments and their rates (as recommended by the label) are summarized below. Treatments were applied with iPOWER handheld pressure sprayer units (which provided uniform droplet sizes), maintaining complete coverage over the entire plot. Irrigation was allowed to continue as per the schedule.

Treatments (sanitizers) and rates that were applied

Treatment Rate
KleenGrow 0.5 fl oz/gal
Bleach As per label: 50/50 dilution
Xerotol 0.5 fl oz/gal
Physan20 0.5 fl oz/gal
Control (water) N/A

We used a scale to rate complete Nostoc coverage on both halves of the plots (both cleaned and uncleaned).

Our preliminary results were very exciting! Before we share, we want to repeat it one more time in the Summer of 2022. Stay tuned for the results!