june 2014 ▲ DIGGeR 25

By Heather Stoven and Jennifer Parke

“What is this green, globby, slimy stuff in my nursery, and how do I get rid of it?”

If you have wondered this, chances are you are referring to Nostoc, a type of cyanobacteria. While sometimes called a blue-green alga, this organism is actually a bacterium that derives its energy from photosynthesis. It can also fix nitrogen.

Nostoc colonies are composed of chains of bacteria that grow on the sur-face of soil, gravel and even cement. When dry, Nostoc is barely noticeable, forming dark, flaky, paper-like sheets. When wet, it swells up and forms conspicuous green to greenish-brown globby, squishy mats that may carpet an entire can yard, especially if the ground is compacted and poorly drained.

The colonies are covered by a jelly-like sheath, which contributes to the colony’s ability to tolerate extended periods of drought and freezing tem-peratures. These characteristics have also made Nostoc challenging to control in a nursery setting, where it has become more widespread in recent years on soil, gravel, and groundcloth.

Impact on nursery productionThe sudden appearance of Nostoc

after rainfall led people in ancient times to believe that it fell from the sky, hence the common names “star jelly,” “star slime,” or “heaven vegetable.”

So, where did it come from? Nostoc is distributed around the world in poorly

Growing Knowledge

An ongoing series provided by Oregon State University in collaboration with the United States Department of Agriculture and in partnership with OAN

▲

Researchers explore treatments for this slime-like bacterium, which causes headaches in nursery production

Close-up view of Nostoc, a cyanobacterium, which can create a safety hazard in nursery production and can also affect the appearance of containerized nursery products.

Nasty Nostoc

26 june 2014 ▲ DIGGeR

▲ nasty nostoc

draining habitats, particularly where phos-phorus and other nutrients are abundant.

But Nostoc is not just a biological curiosity. It impacts nursery production in two ways. Worker safety is the pri-mary issue, as Nostoc is slippery while wet and often grows on hard surfaces and walkways, where workers can easily lose footing and sustain injury. Another issue with this organism is its ability to grow on the bottom of containers, creat-ing an unsightly product for customers.

We conducted field trials in two container nurseries in summer of 2013 to explore physical and chemical meth-ods for control of Nostoc. One nursery was in Clackamas County and the other in Yamhill County. Treatments were tested in 1-meter square plots with four replicates at each site. Treatments were applied twice, two weeks apart, begin-ning in July.

Treatments included:1. GreenCleanPRO, BioSafe Systems

(2 pounds/1,000 square feet, applied as a liquid solution);

2. Axxe, BioSafe Systems (10 per-cent by volume solution);

3. Copper Sulfate, Chem One (2.6 ounces/2 gallons for 1,000 square feet);

4. Heat (propane burner);5. Solarization (Thermax clear 6-mm

anti-condensation plastic film made by AT Films, Alberta, Canada); and

6. Untreated control.Experimental treatments were cho-

sen based on personal communications with growers regarding their experi-ences, and reviews of chemical products and available literature.

Both GreenCleanPRO and Axxe have algae listed on the label for nursery use. GreenCleanPRO is sodium carbon-ate peroxyhydrate, which acts as an oxidizer. Axxe is ammonium nonanoate which is an herbicidal soap that disrupts plant cell membranes.

Copper sulfate pentahydrate, labeled for Nostoc control in water, deactivates enzyme systems and has been reported previously as being effective at control-ling Nostoc. It is not labeled for applica-tion to soil or gravel, however, and may

Photos of representative Nostoc plots four weeks after treatment with soil solarization or copper sulfate at each of two nursery sites, along with untreated control plots.

Clackamas County site in July. Yamhill County site in July.

Clackamas County

Untreated Control Solarized Copper Sulfate

Yamhill County

Untreated Control Solarized Copper Sulfate

Table 1. Scientists treated test plots for Nostoc at two locations, one in Yamhill County, one in Clackamas County, to gauge the effectiveness of various treatments. After six weeks, the coverage and the vigor of the remaining bacterium were rated on a scale of 1–5, with a 5 representing complete coverage or maximum vigor. The average ratings for each site are below. Values within each column followed by the same letter do not differ significantly (p > 0.05).

Yamhill County Site Clackamas County Site

Treatment Coverage Rating Vigor Rating Coverage Rating Vigor Rating

Green Clean 2.5 ab 3.4 a 5.0 a 5.0 aAxxe 3.5 a 4.1 a 5.0 a 4.3 bCopper Sulfate 1.8 bc 1.6 b 1.0 c 1.0 eHeat 3.8 a 4.1 a 3.5 b 3.5 cSolarization 1.0 c 1.0 b 3.3 b 3.0 dUntreated Control 3.0 ab 3.9 a 4.8 a 5.0 a

june 2014 ▲ DIGGeR 27

Your contribution today helps prepare the nursery industry leaders of tomorrow. OREGON

NURSERIESFOUNDATION

The ONF is a nonprofit 503(c)3 corporation. Donations may be tax-deductible; consult a qualified tax attorney or accountant.

Contact the Oregon Association of Nurseries for more information503.682.5089 or 800.342.6401

pose a hazard to fish and aquatic inver-tebrates exposed to contaminated runoff.

The 1-meter plot areas were rated visually on a scale of 1–5 for both per-cent coverage of the plot by Nostoc as well as its vigor. Ratings were performed on three dates: the day of the first application, two weeks after the second application (four weeks after experiment initiation), and a final evaluation four weeks after the second application date (six weeks after experiment initiation).

The percentage of the plot covered by Nostoc was rated as follows:

1 = 0–20 percent of the plot covered with Nostoc;

2 = 20–40 percent coverage3 = 40–60 percent coverage4 = 60–80 percent coverage5 = 80–100 percent coverageThe rating for Nostoc vigor ranged

from 1–5, with 1 representing death or disappearance, and 5 meaning that the bacterium appeared completely healthy and vigorous.

ResultsThe two sites had similar results

from the treatment applications. Some differences between the sites were likely due to initial Nostoc coverage and vigor differences.

The Clackamas County site had extensive mats of Nostoc, whereas the Yamhill County site initially had a number of plots that had spotty Nostoc growth (average rating of 1.9). However, both sites contributed to our knowledge about this problematic cyanobacterium.

At the Clackamas County site, the rating data at the final evaluation (six weeks after experiment initiation) showed that copper sulfate plots had less than 20 percent of the plot cov-ered by Nostoc, with a vigor rating of 1.0 (Table 1). The heat and solarization treatments also had less Nostoc than the untreated control plots at 20–40 percent coverage. The control plots all had ratings above 4 for both vigor and percent coverage throughout the trial. GreenClean and Axxe applications did not reduce plot coverage by Nostoc.

DIG

GER

Mark

etp

lace

DIGGER

Marketplace

Container and B & B

503.390.8486Email: CHNursery@aol.com

“Arborvitae”“Arborvitae”“Arborvitae”

NATIVE NURSERY LLC

‘Roots to grow on’Phone: 541-757-6520 Fax: 541-738-2607 www.sevenoaksnativenursery.com

- Over 300 species grown from seed- Hard to find natives - Drought tolerant, high elevation- Quaking Aspen specialists - Highest Quality bareroot seedlings- Containers from 4”-25 gallon

28 june 2014 ▲ DIGGeR

For the Yamhill County location, when evaluating percent coverage by Nostoc, solarization was the only treat-ment statistically different from the untreated control. Both the copper sul-fate and solarization plots were rated as less vigorous than the untreated control, GreenClean, Axxe and heat treatments.

Although the two test sites showed similar trends, there are likely reasons why some treatments were more effec-tive at one location over the other.

The heat treatment was likely more effective at the Clackamas County site due to a different apparatus being used. The burner used at the Clackamas site (manufactured by Flame Engineering), had a flaming component whereas the burner used for the Yamhill site did not.

We also believe that solarization was more effective in Yamhill County due to the slope of the experimental test area.

▲ nasty nostoc

5 0 3 - 2 6 3 - 6 4 0 5 T O L L F R E E : 1 - 8 0 0 - 8 5 2 - 2 018 E M A I L : W i l lamette@canby.com

See our newly updated website, with all of our off erings & availabilities at www.WillametteNurseries.com

Our customers come to us for our quality rootstock. They come back for our service and attention-to-detail.

c a n b y , o r e g o n

WE SPECIALIZE IN UNDERSTOCK FOR FLOWERING, FRUITING & SHADE.

It’s still Acers to Zelkova, including new Dogwood & more!It’s still Acers to Zelkova, including new Dogwood & more!Value pricing on all our ornamental seedling & cutting liner varieties.

Start planning for next year now. We are stratifying seed for 2014-2015. As your propagation partner, let us know what your needs will be so we can meet your demands.

Nostoc can completely cover a container yard, creating a slip hazard for nursery workers.

june 2014 ▲ DIGGeR 29

Irrigation water accumulated on top of the plastic at the Clackamas County site, reducing solar heating. It is not known why the copper sulfate in Clackamas County was more effective than in Yamhill County.

In 2014, we will continue this work with the help of Dr. Carol Mallory-Smith, OSU weed scientist. We will evaluate chemical treatments with different modes of action that target the photosynthetic pathway or nitrogen-fixing pathway.

Further information on control of Nostoc sp. in Oregon nurseries will give growers more tools to mitigate this expanding problem that affects worker safety as well as other produc-tion-related aesthetic concerns. An inte-grated approach, investigating multiple control methods, may give producers additional options for managing this challenging organism.

NOTE: This report includes infor-mation concerning experimental use of unregistered pesticides or unregistered uses of pesticides. Experimental results should not be interpreted as recommen-dations for use. Use of unregistered mate-rials or use of any registered pesticide inconsistent with its label is against both Federal and State law.

Trade-name products and services are mentioned as illustrations only. This does not mean that Oregon State University endorses these products or that they intend to discriminate against prod-ucts and services not mentioned.

Heather Stoven was a research assistant at the North Willamette Research and Extension Center in Aurora, and has recently been appointed Yamhill County Extension Horticulture Specialist in McMinnville. She can be reached at Heather.Stoven@oregonstate.edu. Dr. Jennifer Parke is an associate profes-sor (senior research) in plant pathology and soil microbiology at Oregon State University, Corvallis. Her email address is Jennifer.Parke@oregonstate.edu. This work was funded by a grant from the Oregon Department of Agriculture Nursery Research Program.

DIG

GER

Mark

etp

lace

DIGGER

Marketplace

Supplies for Small GrowersSEED STARTING - Pots Trays Inserts

Plug Trays__________________________________________________________________________

Labels - large variety size, color &shape of blank plant pot & row markers

_________________________________________________________________________

Weed control, fertilizer, tapes & ties,watering, and more

_________________________________________________________________________

http://www.AAAmercantile.comhttp://stores.ebay.com/AAA-Mercantile

http://www.amazon.com/shops/AAAmercantile

Enter coupon code DIGGER for a 15% discountfor a limited time at AAAmercantile.com

HOSTETLERFARM DRAINAGE503-266-3584

• Plastic Tubing 3"-24" • Laser GradeControl • Open Ditch for Buried

Irrigation • Plows and Trenches •Pot-n-Pot Drainage • Oldest DrainageFirm in Oregon • Newest Subsurface

Irrigation Techniques

Materials andTechnicalAssistanceAvailableCanby, OR

SchurterNursery

Arborvitae–Emerald greenVirescensBoxwood

Japanese MaplesOtto LuykenSkip Laurel

Various sizes & Varieties503-932-8006