Jul 08

Slimy brown scum – it has a name

This brown scum that thrives in our wet winters is called Nostoc Commune

This brown scum that thrives in our wet winters is called Nostoc Commune

Anticipating cultured conversation after a local theatre performance, we retired to the bar for a night cap. But as this is a rural area, talk was all about an entirely different type of culture – a strange gooey, gunky and shiny brown growth.

I’d first spotted it while being a marshal for the Rally of New Zealand. After poking it with the toe of my boot, I decided it resembled seaweed or pond scum – except it was flourishing in roadside gravel. A while later, there it was again – gleaming (in a rare spot of sunshine) on our drive.

That night after the play, I was in the company of many seasoned farmers – who had all spotted its recent arrival, but knew nothing about it.

“I’ll do the research,” I said, “and let you know.”

Northland Regional Council’s biodiversity specialist double-checked with NIWA’s algal experts who confirmed it’s Nostoc commune, commonly called Blue Green Algae.

A mind-dizzying visit to Wikipedia and thereabouts taught me it’s a type of cyanobacterium (blue bacteria) which can live in salt and fresh water, soil and, as we know for a fact, bare rock.

As well as finding out spirulina belongs to the extended family and that there are countless types with long and scientific names, I also know this: “They are Gram positive prokaryotes. They are photosynthetic and have pigments like chlorophyll a, carotenoids, along with phycobilins. They have autotrophic mode of nutrition.” And on and on. Knew you’d be fascinated.

The Nostoc thriving in Kaipara may be the strain known as fallen star or star jelly. It can fix nitrogen, reclaim soil and is so hardy that, after lying dormant for ages, it grows again when exposed to water.

You can, apparently, kill it with various things: salt, vinegar, copper sulphate, dairy alkali cleaner XY12 (full strength or one part to two of water) or possibly glyphosate or algae killer.

As some strains of cyanobacteria are highly toxic, I’d recommend you do more research before you use Nostoc as a food supplement which is what they do in China.

Several people have since told me they reckon it grows where glyphosate (better known by the brand name Roundup) has been sprayed. More research is underway. Stay tuned.

About the author

Rae Roadley

Rae is a journalist, freelance writer and writing tutor. Soon after returning to her hometown to work for Northland's daily newspaper, she met beef and sheep farmer Rex Roadley. He lived in a historic home at Batley on the Kaipara Harbour and after moving there, Rae reported on farming then wrote a newspaper column, The Country Side. Her wryly amusing tales of country life earned many followers and led her to learn more about the local people, past and present. She tells the story of her new life in 'Love at the End of the Road: Finding my heart in the country'.


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  1. Sue Beardslee

    Our 2 small dogs were seen eating it. Both now have intestinal upsets. Could this be caused by it? I sprinkled baking soda on it and it is now gone.

    1. Rae Roadley

      I’ve got no idea – but maybe. I wouldn’t suggest making a meal of it. Glad you dogs came right.

    2. Rod Kane

      Last year after doing some research on google I sprayed it with Calcium hypochlorite which is granulated pool chlorine.
      You can get 10kg of this off trademe for about $65. I mixed up a heavy solution in a 10L bucket using about 1kg and this made about 30 litres of spray which I put into a backpack sprayer. I waited until we had rain and the horrible stuff was hydrated and then hit it. It definitely worked. It started to kill it soon after it started to dry out and a month or so later there was little evidence of it.
      Having said all that, when I left for Aussie in April there was no sign of it, when I came back in October the drive was a mess again. So I have just repeated the treatment and will see what happens over the next month. My drive is close to the Hokianga harbour..like about 30 metres away and it is all metal, however I did the rail trail up there on the weekend and that is infested with it too. This seemed to work but it will be an on-going battle. i will also try the copper sulphate as that is not expensive if you buy 25kg of it.

  2. JOHN Berry

    I used a propane torch on mine and that works fine

  3. Emma

    Hi – last year after reading this blog I tried the option of 1kg of washing soda dissolved in 10L of warm water, applied with a watering can. It works — but only if you use the white powder type of washing soda, not the clear crystals. I buy the powder type in a green bag from Countdown in Warkworth.

    I apply it fairly liberally when the algae is all soft and rubbery after a rainfall. Within a couple of hours it starts to turn from green to yellowy-green and there is an quite an unpleasant smell in the air. Sort of bleach like, with a seaweed aftertaste.

    Within a couple of weeks the slime will disappear. Most of the gravel driveway around our house is free of large amounts, but it does require semi regular upkeep as bits come in on tyres and recolonise the area. I’m still treating the rest of our driveway, about 200m, and hopefully one day soon we’ll have it mostly under control.

    1. Rae Roadley

      Thanks for this.

  4. Andy Sealey

    I recently moved and into a house with a lime chip driveway. As soon as it got wet I ended up with vast mats of this horrible unsightly Nostoc. I can confirm that I have successfully used copper sulphate for the control of Nostoc. Nostoc is a bacterial colony and copper is a natural bactericide. I just sprinkled it on after it had swollen in wet periods. Dissolved in water will also work at rates between 30-50gm / litre.
    Copper is so effective in controlling bacterial that it is now being used in Hospitals in other parts of the world. Taps, door handles, push and kick plates and other areas with a 90% reduction in post operative infections and MRSA.
    Best place to purchase is at Farmlands for $22.00/1.5kg (as at 25/2/18) Farriers will also stock it as should Wrightsons PCG

  5. Andrew McLaren

    We are in the Kaipara Flats area, and have had success with spraying with a copper sulphate (bluestone) solution. The idea was that its basically an algae, and algae’s don’t like copper!

    My trial patch was when the nostoc was fairly dry, and sprayed it with a hand sprayer at 20g/litre. Nothing appeared to happen for a number of weeks, but suddenly realised that it had almost disappeared from the test area.

    For the drive (around 400m) and gravel around the house, I did 200L at 30g/litre. The normal sprayer does around 200L/hectacre, but probably a bit higher dosage than this as took it slow. When applied this time the nostoc was still damp, but no longer swollen.

    The surprise here was the next couple of days, which smelt like a trip to the seaside – I imagine it was the smell of rotting seaweed that was familiar. Its now 2 months later, and the nostoc is still visible, but noticeably less, and doesn’t swell up at all in the rain. I’m hoping that’s the end of it.

    Copper Sulphate is readily available at garden centres at a price, but places like Wrightsons do 25kg bags at just over $100. Its pretty safe, but would be careful with livestock – I think from memory horses are sensitive to copper poisoning, so would keep them away from the edges of sprayed areas.

    Hope this helps. I’ll keep you posted!

  6. Jim. Black

    Hello. We’ll have nostoc. commune on cold tar asphalt drive. I have spayed for weeds with glyphosate. Has anyone tried potassium permanganate. Condys. Chrystal. As a spray. Came across reference in turf management talking about black slime on golf course greens. Am going to try. Sorted. Moss mould. See how it goes.

    Jim. Ramarama

  7. Geoff

    I got rid of a heavy growth of Nostoc on a shingle drive using C3 cleaner which is available at Farmlands. I sprayed twice at 10 day intervals. C3 is available in 5 litre, 20 litre and 220 litre containers. C3 is not recommended to be used close to waterways

    1. Peter Martel

      Hello Geoff. Can you give me more information on the C3 cleaner? Is it the same product as the XY-12 Sodium Hypochlorite that I used? Thanks Pete .

      1. Geoff

        Hello Peter

        I believe the C3 cleaner is a similar product to the XY-12 Sodium Hypochlorite that you used. It does not have a chemical name as such. It is described as Chlorinated Cleaning Chemical and contains 140g/L available chlorine with recommended dilution of 3 parts water to 1 part C3.
        3 different uses are promoted
        a) correction of dairy plant grade faults
        b) makes water safe
        c) kills moss,mould and algae


  8. Dave

    As previously advised, I have tried Kiwicare Moss and Mould spray on product and IT WORKS !!!
    Have given the driveway two sprays a week apart, and even with all the rain we have had here in North Canterbury, the Nostoc has turned light brown and is gradually disappearing. They say it can take a few weeks to take effect and that seems to be the case. I will be giving it one more spray and hopefully we will be rid of this stuff.

    1. Old Pop

      Kiwicare Moss and Mould sounds like it might be worth a try. Unfortunately, the Kiwicare website says its “products are not currently available in Europe, North America or Australia, and we are unable to ship to these regions”. Too bad! Has anyone tried the product called “Wet & Forget” that seems to be more widely available? BTW, If anyone has tried Washing Soda, please post the results so we can all be informed as to how well it works (or not). Thanks!

  9. Old Pop

    FYI. Yesterday I found another reason why we should not using Round Up. I am providing the website with the info: http://www.rodalesorganiclife.com/food/california-becomes-the-first-us-state-to-list-glycophosphate-as-a-known-carcinogen.

    1. Rae Roadley

      Yes, it’s so convenient – except on a long term basis. Thank you.

  10. Margaret Ibbs

    I had Nostoc Commune on my driveway after using Roundup but have now been free from it for nearly 2years.
    I dissolved 1kg bag of Dry Pak Fine Soda Crystals ( Sodium Carbonate Decahydrate ) in hot water using a 10ltr watering can and then filled with cold water. For an area 20′ X 12′ I used 3 cans. Repeat in 2 weeks. Cheap – Easy – Safe.

    1. Rae Roadley

      This sounds like a plan! Thank you. I don’t know what this product is – where would you buy it?

      1. Cliff

        Hi Rae,

        Baking soda is sodium bicarbonate and would work much like sodium carbonate decahydrate except it wouldn’t take as much mass of bicarbonate to reach the same sodium concentration of the decahydrate solution.

        Has anyone put dry baking soda on this stuff? Here in the U.S. it is possible to buy it by the 50# sack. Maybe the answer comes down to putting up with greenery in driveways like we did before glyphosate. Or maybe bury the weeds in more stone?


        1. Mike

          I have tried baking soda in mass quantity – it turns it a lighter brown and then comes right back.

          1. Rae Roadley

            Oh! 🙁

          2. Pauline

            Its washing soda you need to use. I tried it once last year and it did knock it but you need to use it twice and it needs to be done when it is wet but after you have sprayed it, it needs to dry out. Its recommended that you do it twice but I didnt get the chance before summer came along. I will try it again though.

  11. Dave

    We have tried the Sodium Carbonate method, it didn’t work here in Ohoka.
    Stone chip driveway, have used Roundup, same old story.
    I see Kiwicare have a Moss and Mould spray on product that specifically mention Nostoc.
    Would be interested to know if anyone has tried it, and how effective it was.
    I might give it a go when this rain stops….?

  12. The gardner

    Does anyone have an update on anything that has worked to eradicate it completely.

    1. Mike Rogers

      If you have a small area, then covering with a dense, black plastic works. We have a large driveway/yard and it’s not possible to cover all the areas of nostoc but have killed off large areas. We cover for at least two weeks-and what remains is basically dirt.

      1. Dave

        Hardly practical on a used driveway Mike…..?

        1. Mike Rogers

          True, Dave but we got so annoyed with the stuff. Also, the nostoc seems to accumulate on the side of the driveway…twice I nearly slipped on it and down a slope so got desperate.

          1. Dave

            I have posted on here about a Kiwicare Moss and Mould spray on product that has Nostoc specifically named.
            Would be interested to know if anyone has used it and how effective it was…

  13. Peter Martel

    Hello Rae
    What an interesting site. I too have the dreaded Gorilla snot. I have experimented for 4 years, Starting with the obvious use of products, salt, vinegar, Baking soda, wet & Forget ( diluted solutions through to a neat mixture) Hot water, all ranges of acids & Alkali products, Nothing has worked so far. Burn’t it off last summer, when it turned into a black potato chip, got rid of it until it rained then Whommmph, a tiny wee piece exploded into a jelly like blob 10 times the size. Yes, Round up does affect the growth of the Nostoc, I have a block of land where spraying is necessary, Nostoc only appears on the loose gravel surfaces that have been sprayed with Glyphosate. Man this stuff is tough. If its edible the Mars landing crew should take it up on the 1st trip nothing will kill it. I’m Still experimenting and often tune in to read how everyone is progressing. I will let everyone know if I strike it lucky. Pete

    1. Peter Martel

      A follow up for the people that are interested. I think I have sorted the Nostoc problem, As you all know & read my post I have tried numerous products to rid my property of the dreaded gorilla snot, well, i bought some sodium Hypochorite Sanitising liquid, mixed it at a 1part – 2parts water & bingo it started to disappear, I hit a second time & its now all gone. I did spray it at its peak, in other words when it was a real jelly type rubbery solution. I think it will rear its ugly head again when I spray this summer, if it does at least I now know what to treat it with.
      Sodium Hypochorite is used in cleaning of milking machine equipment and other types of things that require sanitising. It is available through most farming outlets. Farmlands, RD1 etc.
      I experimented, at the same time, with Moss killer as well, it worked but not as good as the XY-12 sanitiser. Good luck people.

  14. CarolLynne Cole

    Hi there…same issue here from using Roundup which has a chemical reaction to metal. I understood the Glyphosate you sell does not have that ingredient that causes this…if I am wrong please correct me as we are still using your product from Rainbow Brown. I read extensively on this problem also. What I read was industrial bleach….and it worked. I also used a blow torch on some that i swept up when dry…that worked to. When it is dried we use a leaf blower and blow it away from property into wood chips in garden area which is quite large. It has not grown back there so that is another way. I tried straight white vinegar and it turned the light brown to die…but still swear by the industrial bleach…the stronger the better. The problem is, if it rains (which is not a problem now unfortunately) the ones we miss float to another area…this has wreaked havoc on my parking lot which is huge. Under boats and caravans….ugh! So I bought a 10L canister of bleach and put that in my sprayer and covered every area I could…I used it all…the places I missed will show as soon as it rains and I will do again. No more Roundup in my home…..down the drain it goes. But I do need to know about your product…does it have same ingredient that causes this mess?

  15. Adrian

    Our Nostoc community lives on a Gravel driveway over a limestone base in Kaipara Flats, New Zealand. I am staggered at how World-Wide this stuff is – there are not many plants in common across such far flung points on the globe! It definitely sounds like the beginning of the end of the World. Our ‘tribe’ has only appeared in the last 2 years, since we started using Glyphosate (Roundup) weedkiller to control weeds. They are extremely slippery little suckers and have caused numerous accidents so we are keen to get rid of them.. if we ever can! I have tried Weedkiller (which i now realise just made things worse) also Copper Sulphate, Salt and Shovel. I’d try the Flames of Hell but I don’t want to burn the house down. We also have 2 dogs – whilst the Oven Cleaner sounds effective (if a little expensive over a long driveway) I’m worried the effect it might have on the dogs? And will any run-off damage the lawns?

    I s there no National Emergency been declared anywhere yet? I suggest we get the Governments of the World to unite – and take Nostoc seriously, before it takes over. 🙂

    1. Rae Roadley

      Hold off from calling a worldwide emergency. If you see the post that came in just before yours, washing soda – sodium carbonate – may do the job. I think in NZ, you can buy it from Bin Inn – I’ll try tomorrow. Re oven cleaner – agree on both counts – spraying all that poison around would feel illegal. So . . time to try the next method. Hopefully it will be a goer. The farmer – my husband – had a crash landing going to get the newspaper the other day – hopefully this will prevent an encore.

      1. Steve Dowle

        Sounds an interesting option. I attacked it (in England by the way) last year with Armillatox. The pre-EU legislation, non-water-based stuff. Strong solution, stunk like hell for four days, but kept it at bay…

        … until the last few weeks and slowly, slowly it’s coming back. Not as bad as last year, but it’s coming. I’ve got a little left from my stash, so will attack it again. Then I’ll go online and see if I can buy it anyway in the world. Probably going to be unsuccessful with that.

        So, sodium bicarb sounds a VERY low cost and eco-friendly alternative. Please keep the forum informed!


  16. Pauline

    Googling once again re Nostoc Comune which is spreading on our driveway I found another forum where success has been had by several people. This was gardenersworld.com. A lady there had tried dissolving 1 kg of sodium carbonate (washing soda) and making up to 10 litres and spraying, repeating this 2 weeks later. Has had positive results. Sounds like it is better when its in its wet state (easy in Northland at the moment).

    1. Rae Roadley

      Washing soda – thank you! Sounds like a possibility. Will try it myself and hope others do as well. Maybe we’ve cracked it.

  17. jake

    Has anyone tried to burn it off using a lpg blow torch when its in a dried state?

    1. Rae Roadley

      If you dredge around the comments, I think you’ll find that someone has – and one person threw petrol on it and then a match. Posted the photos. Dramatic.

  18. Anita

    It has now been 2 months, and the algae treated with ph decreaser looks like it is still killing off the algae, as the dead plants are continuing, further down the sloped driveway, so must be affected by rain washing the acid there.
    I also covered another area with a big mat of Artificial grass, which is heavy and dense,and it looks to have suppressed the Nostoc. Don’t know what will happen when I remove the mat, though?

    1. Rae Roadley

      Let us know at mat removal time. Thanks.

  19. Colleen

    Hi, we are in Rotorua and have a limestone gravel parking lot. It is covered in this triffid like substance, but unlike the triffids this pest doesn’t die in salt water.

    I have tried straight black, boiling water, salt and finally wet and forget. Thus far nothing has worked short of picking up the little monsters when they are wet and fat.

    In the past we gave used Roundup on the weeds and this fuelling the fungus.

    Someone mentioned oven cleaner way back in the threads. Does anyone have any solution? Cheers!

    1. Rae Roadley

      Hi Colleen, If you check out the thread after this blog, people have tried all sorts of things – and some appear to have worked and they may do the trick for you as well.

  20. Anita

    I have just tried altering the pH by sprinkling a swimming pool PH alkalinity reducer (dry acid) AND IT WORKS!!!!
    My patches of Nostoc algae on my limestone chip driveway are dead, overnight. Will be interesting to see if this method stops it returning. I have used roundup for the odd weed, in the past 2 years. I am in Kerikeri, Northland.

    1. Rae Roadley

      Well, big yay to you! This sounds simple, effective and low cost. Please let us know if it works.
      It also sounds less thrilling than the method employed by the gentleman who put flammable liquid on the stuff and burned it off – something I suspect most of us would prefer. Thank you!

      1. Mike Rogers

        HI Rae

        That does seem promising. Just an update re our covering the nostoc. It has been a couple of months now and all the algae covered has died. Of course it’s tricky to cover all of it but we have eliminated nostoc from the most important areas.



        1. Rae Roadley

          Thanks for this. To save anyone digging back through posts – Mike’s covered it with dark plastic to try and suffocate the life out of it. Seems to work.

    2. Old Pop

      Anita, I really like your idea! I have also been toying with the idea to try a alkaline soil reducing product sold by home and garden shops. It is known as Aluminum Sulfate. I don’t know how the Aluminum Sulfate and the swimming pool stuff compare. Please let us known more details on the swimming pool ph reducing product used, i.e., Brand, Active Ingredients with their concentrations and the amount you applied (a sprinkle or a coating), etc. I am still testing my oven cleaner stuff and it looks good so far, although your idea may be better way to go.. Keep testing!

    3. Old Pop

      After sending my last post, I forgot an important factor. Please let us know if the swimming pool ph reducer was applied when the algae was in the dark green jelly-like state or was it applied when it was black crisp-dry state? I don’t know about others but I have an extremely difficult time identifying the Nostoc algae in the black crisp-dry state. I have found the oven cleaner works when the Nostoc algae is in the jelly-like state. FYI, The oven cleaner also works overnight and turns the algae a light brownish color. I’m still testing…

  21. Old Pop

    I have had the Nostoc Commune algae on my gravel driveway in Virginia for two years now. This has been verified by Virginia Tech. I’ve tried all the recommended control products and nothing has worked. So I did some tests last year on individual Nostoc algae samples in my garage. I applied all kinds of household products and nothing seemed to kill it but one did. The product that killed the algae samples every time was Oven Cleaner…yes OVEN CLEANER!!! I’ve tried several different Brands: Easy Off (Fume Free); Easy Off (heavy Duty); Carbona (Fume Free & Biodegradable) and Goo Gone (Oven and Grill Cleaner). They all worked to kill the algae!!! I do not know all the ingredients each of these products contain because they are not listed.
    I have not tried any of these products on my driveway to date but plan to do that soon. Maybe some others can try this and let us know how well it worked.

    1. Rae Roadley

      Thanks for this – and for taking the time. Sounds good – and thanks for the detail on fume free and biodegradable. Check out the next comment that’s just come in – swimming pool Ph alkalinity reducer did the job overnight – but will it last? We shall see.

  22. Mike Rogers

    Hi Rae

    An update re covering the nostoc; it seems to be working, after a failed chemical campaign. I usually leave the black plastic for a couple of weeks. Of course, it’s difficult to cover all of the algae but I’m prepared to make this a long campaign. We were becoming quite concerned, as we have a steep driveway and our car lost traction twice last winter and went close to going down a bank. Thanks to Phil for the update re toxicity. Cheers.

    1. Rae Roadley

      Mike – thanks for this. Glad the black plastic is doing the trick! Something needs to . . .

  23. ruth wynn

    I’m interested if anything has been found out about the toxicity of this Algae? My kids play on the driveway all the time…

    1. Rae Roadley

      Hi Ruth,
      Toxicity – a good question. We haven’t discussed this – with luck, this will be seen by Mike, a scientist who follows this thread, and he’ll answer. I recall that some types of nostoc can be used as food – so have an idea it’s not toxic. You could try the idea Christine has – her comment came into the thread at about the same times as yours. Please advise any findings.

      1. Phil Novis

        Hi Folks

        Just to note that the Cawthron Institute tested a sample of Nostoc commune from Lake Taupo and detected toxin genes. There is at least one anecdotal report of a dog poisoning in NZ. Don’t eat it.


  24. christine pedersen

    Hi Rae, I am so happy to have found your blog on this horrible Brown Slime.
    We are in Warkworth on a lifestyle block with compacted lime rock base, topped with gap 40 & gap 20 metal .
    We have had this unsightly brown slime on drive verges for about four years.
    My theory is that it has come in from the various quarries on truck tyres when topping the drive.
    In the past I have scooped it up with a dust pan while it’s jelly and disposing in rubbish bags. Gets a bit heavy.
    I also have swept it up when dry. Unfortunately any bits you miss just regrow and multiply.

    This summer, aided by drought, I would wait for rain to swell the algae in the worst areas then wait a day or two until it dries to a complete film (like a sushi sheet) then SUCK them up with a black&decker outdoor vacuum.
    I have recently covered a huge area with great success using this method with NO regrowth after the rain. Yaaaay.
    I have found the wind dehydrates the slime quite fast so keep a watchful eye. If it dries too fast it breaks easily and forms new clumps when the rain comes.
    I will continue my mission using this method wiping out the worst edges until I hopefully get it under control.
    I hope my message helps some people combat their algae problem. cheers christine pedersen.

    1. Rae Roadley

      Hi Christine,
      This sounds like a really clever and effective approach – well done – might be useful for the next person who’s asked about its toxicity.

    2. Debbie

      Hi, I work in a plant nursery in Whangarei, we have had this ‘gorilla snot’ (as we like to call it) problem for 4+ years. We have tried all sorts. Vinegar, bleach, copper, algaecides, moss killers, shoveling it away by hand (thats how thick it was).
      Anyway at the moment we are trialing salt, big 25 kg bags of the stuff. It is definitely helping if spread on thick enough and it is a reasonably cheap option. I think we will keep applying the salt as needed, and i’ll keep you informed as to how successful it was. I dont think we will ever be completely rid of it as we have such ideal conditions for it to grow. Regular irrigation and metal walkways everywhere. It doesn’t help that it is so easily spread. A few bits on the base of your boot, you walk thru the nursery and there’s patches springing up everywhere.

      1. Rae Roadley

        Thanks for this salt idea and for taking the time to share it – maybe rising sea levels will solve the problem in the end.

        1. Rae Roadley

          Thanks muchly for this – most helpful – doesn’t sound too poisonous, which is good.

      2. peter

        Hi . How dose the salt affect the viability of the soil ?

        1. Debbie

          The salt if used often enough would not have a good effect on the soil. However as most often this Nostoc commune is found on gravel driveways it wouldn’t matter would it. I would be wary if I had a vege garden or similar right next to where you are applying it though. We are still battling this horrible weed with salt. It does work but it isn’t a permanent solution as it seems to pop up elsewhere. The original patch may be killed off with the salt but of course because it is so easily spread I don’t think we will ever get rid of it completely. We find even with rain or irrigation it gets spread, we quite often find it popping up where water has been running down to the lower levels of the nursery.

  25. Steve

    I was in the garage, getting ready for more assault on the Nostoc Commune, when I spotted some old Armillatox from when I was treating my last property for Honey Fungus. I remembered Alasdair Sutherland’s comment, so tried a strong solution of that and so far so good. It has turned a very dark, hopefully unhealthy brown colour.

    AFTER using it I thought I’d research the new Armillatox and discovered that the old formula has been banned as a herbicide in the EU for uses other than as a disinfectant.


    Well anyway, so far so good. Let’s see if it does the job long term.

    1. Mike

      Thanks for that.
      Good luck. My place looks like a beach full of seaweed. Have tried two different commercial mixtures so far. Each has changed the colour of the nostoc. but no die off as yet. I am presently trying to stop photosynthesis by covering it with plastic. Am hopeful, although it will take months to cover the whole area.



      1. Rae Roadley

        Comment from a Maungaturoto local: I’ve had good success with getting rid of “gunge” on our driveway using a solution of 10% Janola 100% water. I use a watering can and spray it a couple of days after rain when there looks to be a day or two of fine weather ahead. It still comes in from the road inevitably but I have it pretty much under control. (The idea comes from another local.)

      2. Steve

        So far, the brown “dead” appearance is holding, despite having plentiful rain to reinvigorate the Nostoc. This weekend – weather providing – brings an interesting test. I’ve got to spray the weeds which means glyphosate based weed killers, which Nostoc sees as a good healthy fertiliser by all accounts, so if it’s truly dead, it should stay dead. If it’s only stunned or dormant, the glyphosphate will kick it off again.

        I didn’t say previously, but I missed one small patch and decided to leave it as a control. It’s not shrivelled yet and still looks happy. Again, let’s see whether the weed killers feed it or not.

        1. peter

          how long have you covered the nostoc

          1. Steve

            I’ve not covered the Nostoc. I sprayed it with a strong mix of old-formula Armillatox (the phenol based version). Used 1.5 to 2 times the strength of that used for Armillaria (Honey Fungus), so very strong indeed. As I say, so far so good.

  26. Steve

    I’ve just bought a house in the country in Worcestershire, UK, and have a gravel path and you will know where this going! Seaweed looking stuff. Initially I thought it was some kind of faeces, maybe wildfowl or something… (There are pheasants kept somewhere around here and I often spot them in my garden).

    Unlike most of your contributions, I have yet to attack the problem, because I was researching it first… Stubborn devil to get rid off eh? That’s hardly surprising according to one site I found… It’s called an “extremophile”. This is why, from: http://www.downgardenservices.org.uk/bluegreenalgae.htm.

    They can be found in water and on land, and are able to withstand extreme environments such as the freezing Arctic or the hot pools near an active volcano – for this reason they are known as extremophiles. They also have the ability to lie dormant for long periods when conditions are unfavourable and come back to life when rehydrated.
    Aquatic forms are responsible for the algal blooms which appear in water bodies. These can be hazardous to other wildlife and in inland water are toxic to animals which ingest them as they drink. The main cause is the phosphate in runoff water from intensively managed agricultural land.


    Geological studies have found that oxygen-producing cyanobacteria were present about 2.8 billion years ago and are probably responsible for the creation of the life-supporting atmosphere of the Earth. They have survived catastrophic phases in our evolutionary history, such as large scale volcanic activity and total icing over of the planet. The light reactive molecules they use are similar to the rhodopsin protein which acts in the light sensitive receptors in our eyes. This gives a link back to when these chemicals first appeared and have remained in the genetic code of cells enabling animals to develop sight.

    Seems like it’s been around a long time and is very resistant to just about everything. If anyone has had any real success, I’d love to know. I may start with the controlled flaming approach first. Certainly not going to use any glyphosphate products like Roundup, but I suspect that my predecessor did, which is why there’s so much in my drive. Maybe burning it off followed by bleach will do it. I don’t think flames alone will kill off the plant entirely, not when it grows near volcanos!

    I’ll keep you posted.

  27. Mike

    We have the worst infestation yet-almost double this year and we use glyphosate on the limestone driveway… local plant expert used ’30 Seconds’ (green) so we tried that. The algae has changed colour but no die-off as yet.

    1. Rae Roadley

      We’ll stay tuned for updates.

  28. Ian Evans

    Hi, We live in East Anglia, UK, and first noticed it this year on our gravel drive shortly after using glyphosate (the active chemical in Roundup, of course). Reading round the subject, I note that phosphate fertiliser runoff strongly encourages Nostoc growth and I wonder if glyphosphate slowly breaks down in soil to release phosphate thus setting off the ghastly Nostoc!

    I have found that if we apply domestic bleach (at about 50 % dilution) on damp days, so that the area stays wet for several hours, the Nostoc is bleached to a light brown and looks sickly. I’m not sure yet whether it will recover, but here’s hoping!

    1. Rae Roadley

      Thanks – another potential solution. Strange that everyone’s noticed it so recently, when presumably it’s been around as long as this good earth we live on.

      1. peter

        Hi . going to try a hunkin flame weeder.. I note that my neighbor across the road who has never used glyphosphate dosnt have any of this horrible stuff.

        1. Rae Roadley

          We await the results with interest.

          1. peter

            burning it to crisp works . But very slow . just heating like weeds and it seems to come back . I think for my main drive area i front of house i will just get down to picking up when dry as then it is easyer to pick up .

  29. Sue

    Has anybody been able to find any information as to potential toxicity of this algae? I am really struggling to stop my dog from eating it every chance she gets. I work at a Vet Clinic and can find no information in any of the Veterinary texts I have read.

    1. Rae Roadley

      Let’s see what people have to say. Change the theme of this conversation if your dog is onto something nutritious.

      1. peter

        Our dog wont eat it . Can you tell us what type of dog you have . We will get one the same to eat our nostoc.!!!

        1. Sue

          Haha hadn’t thought about it from that angle 🙂 Dobermann puppy, when I find out if it’s not toxic I can let her tidy up our driveway and then bring her round to yours. Save buying dog food 🙂

    2. Mike

      We have a chihuahua at present and have had a border collie, retriever and a dobermann. No indication of any toxicity but I believe there are many varieties of nostoc.

  30. Mike

    Ok guys, as I have posted, I have tried: straight bleach, vinegar, baking soda, every anti-fungal and roundup type product I could think of and NONE of it gets rid of this stuff. So my 11 year old son and I went down this past weekend and found the way to get rid of it 🙂 See below… Hopefully the video posts right:


    Pump sprayer (ALL PLASTIC! NEVER USE A PUMP SPRAYER WITH METAL PARTS!!!) with straight gasoline. Soak the stuff and let it absorb for 5 minutes… Then light a match and stand back… Oh, and don’t tell his mom 🙂

    1. Rae Roadley

      Here’s the video. I’m watching it now.

    2. Rae Roadley

      Golly, Mike – my quiet and unassuming little website is moving into new territory here! My dad once lit a fire with petrol – after the explosion – which wasn’t large (and we lived in a quiet, dead-end street), people phoned the fire department. We were eating dinner when an army of silver-clad firemen exploded from the native bush on the hill by our property. Got a telling off and a good story. Best that this is done in winter – but will it come back again? Might not be worth the toxic fumes if it does.

  31. peter

    hi . any up date on what kills this stuff. Heared Rood on the radio recently , The wet and forget people said their suff killed it . Has anyone tried this.?

    1. Rae Roadley

      Haven’t heard of anyone using that – might it not wash away and annihilate pretty nearby gardens. Perhaps salt – that’s the latest idea.

    2. Moreen

      I have tried copper sulphate, spraying at fortnightly intervals and it appears to be working. your local farm centre or garden centre will sell it. it is most probably the same base as the wet and forget, except will be cheaper.

    3. Mike

      I would love to see if someone would try this “Wet and Forget”. I would be surprised if this works, as even straight bleach has not killed it for me, but maybe there is something special about this product… If I hadn’t already burnt all of mine up (see above video 🙂 ) I would try it… Would love to know if this works, though, for future reference, as I can guarantee I will be dealing with it again in years to come…

      1. Rae Roadley

        Anyone up for using ‘Wet and Forget’? Please let us know.

  32. Kevin

    I’ve been reading comments about this fugus and tried many things to eradicate it. As a last resort I went to the local RD1 store and purchased a 25kg bag of fine salt and spread it across the worst patch of my driveway and waited about two weeks and it seems to be working. It goes a light brown and doesn’t regenerate after rain. It seems to work but you don’t want to spread the salt where runoff may go into a garden. Salt is very cheap (about $13 for 25kg). If you have any doubts, get the salt container from your kitchen and spread it over a small square of it and see how it goes. tI also kills quite a few of the weeds in your driveway as well.

    1. Rae Roadley

      Good old salt – sucks the liquid out and maybe will be the secret weapon everyone seeks – when used with care. Thanks.

  33. Peter

    Hi Rae
    Have you heard of benzalkonium chloride be used as a treatment. Quats as they are known have good efficacy against moss/mold/algae.

    1. Rae Roadley

      Nope, haven’t heard of it – but maybe someone else has – and has tried it. Rae

  34. Kath

    We live in Wellsford/Port Albert. Nostoc’s the worst it’s ever been, on the drive in front of the garage (where I have several times in the past sprayed with Glyphosphate for weeds – which I no longer do). Around the back of the house, same conditions, in fact better conditions, – there’s none. And that area has never been sprayed with Glyphosphate. I am sure there’s a connection Glyphosphate’s used world-wide, this stuff appears world-wide. I rang NIWA a couple of years ago for information – first time I had ever heard the name. It seems by using glyphosphate we are creating an environment for the stuff to thrive. Is Nature trying to teach us a lesson? Certainly it likes the interstices in the limestone, nice little pockets of water there. Shrivels up in summer, just waiting for winter. It’s all down the sides of the roads in the area, anywhere there’s limestone. I rang Auckland Council a year or so ago, they’d never heard of Nostoc (!!). Hopefully they have now. They said then that they use glyphosphate to spray the road edges for weeds. It’s great to read all these posts.

    1. Rae Roadley

      Yes, we all think glysophate is THE thing, and for good reason (goodbye kikuyu, at least for a little while) – but have no idea of the long term effects.

  35. Mike

    I started spraying a generic “total vegetation killer” on my gravel driveway to get rid of the weeds and grass about 5 years ago and over the past 3 years this has now taken over. I have tried about every shelf-product including algae killers and fungus killers and nothing seems to work. I ordered 27 lbs. of baking soda online and will try this next, but have there been any reports of solutions for this unbelievably hardy nuisance?

    1. Rae Roadley

      Please let us know if the baking soda works.

      1. Dana

        Did Mike get back to you re the baking soda trial? Any other ideas or solutions? We are in Mangawhai and this stuff spreads further every year!

        1. Rae Roadley

          No, Mike hasn’t got back – but he follows this thread – let’s see if he’s keeping up. Mike . . hellooooo . . . any developments. (If this fails, I’ll drop him an email.

          1. Mike

            Hi All! I haven’t forgotten about you all 🙂 The property where I have this problem is a weekend getaway location, so I am no always there to observe. However, what I did was I spread the 27 lbs. of baking soda on the right side of the problem area and sprayed vinegar on the left side. I noticed the last time I was there the left side looked no different but the right side appeared “lighter”, almost a golden color. I will be going again this weekend and will look and see if it has killed the Nostoc in either area and let you know… So far, though, definitely not dead… My last resort will be to put gasoline in a pump sprayer and spray 5×5 foot sections and flick a match…. I think that will indeed do the trick if nothing else… So frustrating though – nothing really seems to kill this stuff. I did spray the vinegar on it when it was in its dry/flaking form so it absorbed, but again – no change on that side at all as of last weekend (after 3 weeks after spraying)…

  36. Roz

    We’re in Puhoi and we also have this Nostoc Commune everywhere on our gravel driveway where we have weed sprayed with glyphosate. It seems to be worse in wet parts of drive. Has anyone had any success getting rid of it? Is there a Better weed spray that won’t cause this Nostoc to appear?

    1. Rae Roadley

      Seems weed sprays don’t do a thing – a couple of others have recently left comments which you might like to read. And thanks for visiting.

  37. Holly

    In Northland we have it. Some people have said that RoundUp weedkiller can help it grow. Do you know if this is true?

    1. Rae Roadley

      Yes indeed. RoundUp is a brand name for the herbicide glyphosate – and if you look at the various posts, you’ll see that it’s pretty much a fertiliser for Nostoc. Wondering if heat might kill it – someone I know is giving it a go with one of those blow torch weedkillers – I’ll report on progress.

    2. Moreen Kaipara

      it flourishes in lime driveways and sea shell, it is caused by poor drainage. it is not caused by weed spray and weed spray will not kill it. I have sprayed with straight bleach and still it survives. Nostoc commune is a terrestrial species regarded as a “form species” (Wright et al. 2001), meaning that a number of indistinguishable species are involved. It is a blue-green alga that occurs worldwide, and is particularly associated with limestone, coral and other calcium-carbonate-based rocks. It can be a nuisance on limestone chippings, limestone or coral paving, and is often mistaken for a seaweed. When dry they are unsightly, often being mistaken for dried dog faeces, and when wet they can be rather slippery. The bead-like form can be swept up and the rubbery sheets are easily lifted. The loose jelly can be swept up as well. On hard surfaces bleach or a similar cleaner should kill any that remains. Improved drainage, and increased fertility (particularly N and P based fertilizers) will discourage its growth. Michael Viney in the Irish Times advised: “Apply a chlorothalonil- or mancozeb-based fungicide to the infested area once every seven to 14 days until the nostoc is dead.”
      Growths also occur on limestone chippings used as ballast on flat roofs, particularly on school and university buildings in Britain and Ireland. In damp places, granite chippings should be preferred to limestone.

      Most of this info comes from: http://www.seaweed.ie/algae/Nuisance_blue_green_algae.php

      Most websites relating to this “Nostoc” link it to compacted poor draining soil, which usually are lime stone/ rock driveway or areas with sea shell as they also contain calcium. I also live bordering a farm and they spray lime fertiliser from the air which most probably does not help.

      I spoke to Hilton Furness of Auckland Council and he suggested trying copper sulphate, but other sites say this does not work either. I have just sprayed again today with triple strength copper oxide in the hope this may work, but it appears to be near indestructible.

      (The part about the roundup and glyphosphate spray is incorrect and is more about where people mainly spray (compacted lime driveways).)

      Another article I read (perhaps on the site listed above) credits Nostoc with weathering and aging of limestone buildings in England.

      1. Rae Roadley

        Thanks – very helpful. Seems this stuff is indestructible. The sooner someone figures out how we can turn it into food for, say, livestock (rather than, say, us) the better.

  38. C.P. AMbers

    Very interesting your note about Nostoc appearing after glyphosate treatment of driveways. Here in northern Ohio (USA) we never had Nostoc goo until we started using glyphosate on our limestone driveways. Soon after the first use of glyphosate, the colonies appeared and they grow through the spring and fall. In all of the places I have noticed it here, the gravel contained limestone (CaCO3 and therefore is alkaline), and folks had used glyphosate to remove weeds. I hypothesize that the glyphosate it killing one or more organisms that would normally compete with the Nostoc and keep it in check such as green algae, diatoms, or protozoans. This is a fascinating research problem that field observations are suggesting be studied in more detail. Glyphosate is promoted as being bound up in the soil as soon as it hits the ground, but this suggests it does a fair amount of broad spectrum damage to soil microbes to the benefit of at least Nostoc before it is inactivated by soil adsorption and bacterial breakdown. It may even be possible the Nostoc is breaking it down itself into nitrogen and phosphorus compounds it can metabolize. This would make glyphosate “Nostoc fertilizer!” http://en.wikipedia.org/wiki/Glyphosate

    1. Rae Roadley

      Very interesting point re the limestone – we are on limestone country and have a limestone driveway on which Nostoc thrives. Thanks so much – and yes, seems to glyphsate is indeed fertiliser for this ‘goo’.

  39. Christine Browne

    Thought you might be interested to know that we too have the dreaded Nostoc commune problem here on our small farm in France. I think I first noticed it about a year ago and now it is absolutely horrible and covers a large area of our garden which is gravelled (not very well, it’s a rather thin layer and needs a new application of gravel). It is unsightly and alarmingly slippery. I have got to the stage where I concerned enough to have started looking online for answers in order to try and eradicate it. I read earlier that baking soda works and think that is worth trying. I will also contact Phil Novis to see if he has any further advice. Many thanks for the info.

    1. Rae Roadley

      It’s amazing where this stuff pops up – and now that it’s summer it’s quietly hibernating waiting for the right conditions.

  40. Mark Rowse

    Hi Rae, Do you know if anyone is still following up on this or has it become just too hard? cheers, Mark

    1. Rae Roadley

      Hi Mark, I assume the guy who commented on this post last year is still working on it – at least in some small way. Other than that, I can’t help you. Some people say this stuff grows where RoundUp has been sprayed, but it appears to me that it enjoys a perfect storm of moisture, sunlight and shade. If you find any answers, please let me know. And thanks for visiting.

  41. Rae

    We have had the stuff around our farm sheds for at least 10 years. It has now spread to gravel areas around our house and also on shell paths in my garden.
    We have tried so many chemicals and nothing works. Our latest recommendation is moss killer sprayed yesterday so will see if that works. Im not holding my breath!
    We have had it identified as Cyanobacteria.
    Its now growing in the gravel on the sides of roads in this area.
    We live in Karaka, South Auckland.

    1. Rae Roadley

      Yep, it’s tough stuff to budge. I feel increasingly sure it grows where Glyphosate (Roundup) has been used and in areas that get a specific amount of sunshine, i.e. not to much or too little (no scientific tests have been conducted to verify this). And thanks for confirming I was on track with its identity.

  42. bob

    I have it in my garden in the UK and keep it under control with Bordeaux mixture applied directly to it. As it is a copper based mixture you may be able to use copper sulphate.

  43. Keith

    We have it here in Nelson, NZ.

    So far I have sprayed it with undiltued bleach and have also sprayed the affected driveway with diesel; both of which cetainly curb its enthusiasm (compared to untreated areas) but do not kill it off, alas.

    1. Rae Roadley

      Thanks for letting me know – wow, it’s tough stuff. Let’s hope it turns out to be edible – or at least useful. Hopefully the answer will emerged soon.

    2. Viv Hamlin

      We’ve had it for years on our metal driveway in Whangarei when it’s really wet. I’m sure it’s Liverwort…

      1. Rae Roadley

        Googled Liverwort – http://www.teara.govt.nz/en/liverworts-and-hornworts/page-2 – and it appears to be mostly green. The slimy gunk is brown and it doesn’t have leaves and it dries to a crisp and disappears in dry weather. The Landcare guy following this blog – he commented earlier – might have a thought, though he’s probably doing the sensible thing and is holidaying. Merry Christmas! Incidentally, my next column in the ‘Advocate’ next Saturday is about this blog which has got more comments than any other.

        1. Phil Novis

          Hi folks, not on holiday yet unfortunately but not far away! Liverworts – these occur in several forms including leafy and thallose (e.g. Marchantia). Thallose liverworts could possibly be mistaken for Nostoc, although as Rae mentions they are typically greener, and they don’t have the same rubbery texture. They also attach to the soil using rhizoids (root-like structures), unlike Nostoc. Liverworts also have more structure in other ways: thallose liverworts often have gemmae cups, which are little cup-shaped structures containing baby versions of the plants. Microscopically they are very distinct. Liverworts are embryophytes (land plants) whereas Nostoc is a bacterium. Happy Christmas all! – Phil.

          1. Rae Roadley

            Thanks! Unsurprisingly at this time of year, my blog on another type of brown gunk – not an embryophyte or bacterium, but a recipe for Christmas cake – is getting the most visitors. And Happy Christmas to you.

  44. Alasdair Sutherland

    I have a small garden nursery in Inverness Scotland and have it spreading everywhere especially on gravel and concrete paths. I have tried the following with no permanent results.

    Glyphosate weedkiller
    Diquat weedkiller
    Jeyes fluid (new formulation)
    paraffin flame gun
    diflufenican residual weedkiller
    quinoclamine moss killer

    I have read it tends to be worse in areas with poor drainage but perhaps due to the wet season last year and also having to use overhead irrigation this year it has got a real hold.

    I had some success with some old armillatox which I think used to be based on phenols (similar to old jeyes fluid) but the new formulation does not work as its now soap based.
    I am going to try peroxyacetic acid in the following weeks and also sulphate of iron to see if they will work.
    I am also looking into moss killer they use on roofs etc.

    It seems to be indestructible and when wet is a nightmare to walk on especially on concrete.
    I would be very interested if anyone has had any success at all with controlling it.


    1. Rae Roadley

      Hi Alasdair, Interesting – and your version even grows on concrete? Don’t think ours does – it tends to grow in gravel that isn’t driven on by cars and we’ve recently decided it thrives in areas that don’t get all day sun. I’ll let Phil from Landcare know you’ve visited. Have you tried boiling water or one of those hot steam weed killers? I presume your version of the stuff dries to a crust and disappears in dry weather …. assuming you have such a thing in Scotland – we have a friend there at the mo – I’ll double check this when she gets home. Warm wishes & thanks for visiting.

  45. Denyse Montegut

    I live in upstate New York near Syracuse and noticed it on the driveway gravel two summers ago. Coincidentally that is when I started using Roundup on the gravel.
    It is now taking over. Slimy green bubbly mess.
    Researching now for the best way to kill it.
    I will attack it in the spring.

    Thanks for your info —
    I hope to hear more about any further news you come up with.

    1. Rae Roadley

      Hi Denyse, Thanks for dropping by – so interesting about your ‘bubbly’ mess. It tends to be dark brown in NZ and after a few dry and sunny days, it disappears – then returns. Seems boiling water might be the only way. I’ll keep you posted if/when I learn more. Rae

    2. Maureen Sudlow

      Looks like we’re creating a perfect barren environment with that Roundup. Perhaps this algae can’t compete with other vegetation, so it pops up where we’ve wiped it out…

      1. Rae Roadley

        Hmmm – and hi there – maybe, although it seems to me it likes gravel areas that get limited sun. A mystery and certainly entertaining to find that my post popular post is titled ‘slimy brown scum’.

        1. Maureen Sudlow

          there’s no accounting for tastes 🙂

  46. Phil Novis

    Hello Rae, thanks for the interesting blog post. I work at the Allan Herbarium, Landcare Research, and have been sent this stuff to identify numerous times over the years. Everyone always wants to know how to get rid of it. There seem to be some odd things about its distribution. For instance it seems to occur in nursery gardens throughout the country, but responses to a recent enquiry in NZ Lifestyle Block magazine only generated responses from private individuals in Northland. So there could be interesting questions around whether it is all the same stuff genetically, whether it is toxic as you point out, and various options for control (there is literature about the growth parameters controlling the production of the “jelly”; without the jelly it presumably wouldn’t be a problem). I’m interested in trying to get some research going about this, and I’ve had a few people telling me that some is already going on – but I’m having trouble finding out what, and who might be doing it! So I’m most interested in knowing who you might have spoken to at NRC or NIWA (or info from anyone else). I can be contacted at http://www.landcareresearch.co.nz/about/people/staff-details?id=bm92aXNw. Thanks! Phil Novis

    1. Rae Roadley

      Hi Phil,
      Further to my email and attachment, I’ve had a message from someone in the UK – I assume it’s not clever spam. I’ve messaged her with your website address. Rae

  47. CiderGirl

    Wow! It’s like triffids! We have it on our drive for the first time this year,but I have previously seen it down the road in a rough gravelly area – in Somerset, UK

    1. Rae Roadley

      Hi CiderGirl, If you’d like to make contact with Phil at LandCare Research to tell him this, he’d be interested – and thanks for visiting my blog. Also, check out his message on my blog, Rae

  48. Viv Hamlin

    Late reply, but have to tell you that I first noticed this stuff on our gravel drive about 10 years ago. It still appears sometimes when we have prolonged wet periods. We live just south of Whangarei.

    1. Rae Roadley

      Wow! Ten years ago – people I talk to started noticing it last year. I’m thinking it started at your place :o) Thanks for reading my blog and visiting my website. Rae

      1. kiwiskan

        …and it’s been on our gravel driveway ever since we arrived in Dargaville around four years or so ago

  49. Kiwiskan

    Thanks for that Rae. We have that rotten stuff on our drive. It’s unsightly, slippery, and keeps coming back. Good to be able to put a name to it.

    1. Rae Roadley

      Hmmm – and you and many others, it seems. Thanks.

  50. Belinda

    I hae heard that it grows where roundup has been sprayed… not sure, but we have plenty of it on our gravel driveway.

    1. Rae Roadley

      Yes, that’s what people tell me – and I plan to learn a little more. Another peculiarity is that it only appears to have been around for the last couple of years – odd or what? Incidentaly, glyphosate is the chemical name for Roundup – and I’ll make a note of that in hte blog. We journos are trained to call it by that name not its trade name. Thanks!

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