I see that CobCottb tried the soda crystals and I'm very interested in follow up results to see if it sustained. I decided to try a different solution. I found a research report by the Oregon Department of Agriculture that studied 6 solutions for nostoc over several weeks. (Here is the report: https://www.oregon.gov/ODA/shared/Documents/Publications/NurseryChristmasTree/NurseryResearchBlueAlgae.pdf) The best results were achieved using Scythe Herbicide. Their test areas had heavy and healthy nostoc growth and in one location (a nursery) there was an overhead watering system in regular use during the test weeks. The active ingredient is NOT glyphosate (Roundup) which is good since I think Roundup was the instigator for me, and Scythe is a broad spectrum herbicide (http://www.gowanco.com/Document.aspx?id=145) that will probably kill all the things I was using Roundup for. So that's a bonus. I will do the first application in a couple of weeks and will follow up this post with results.
I have a lot of this nostoc on my gravel drive at the moment. I have used Roundup on it in the past, but not for at least 18 months.
I've been doing a bit of Googling and some sites suggest using a herbicide based on pelargonic acid (also known as nonanonic acid). These apparent work by stripping plants of their waxy coating and thus causing them to dry out. It's this drying desiccating action that is supposed to work on the nostoc too. Nostoc is described as "technically a bacterium that derives its energy from photosynthesis".
I don't live in the UK so I shall have to ask around to find out if I can get this stuff here, and if so, I'll give it a go. It seems to be one of the newer generation of products which is supposed to be less harmful to man and the environment, and it's made from geraniums or oilseed rape.
If anyone else has any joy with any of the other methods suggested above, I'm sure we'll all be very grateful to know.
I am delighted to report that the cheap and easy method suggested by Margaret Ibbs has eliminated the substance from my gravelled driveway. I made up the solution as described and sprayed twice, approximately two weeks apart.
Over the last 6 years this substance had grown to cover an area measuring 18mx4m and was not just unsightly, but also dangerous to walk on. I tried herbicides, bleach, disinfectant etc. From time to time I checked this forum to see if there were any new ideas. The soda crystal solution is a real gamechanger. Well done Margaret Ibbs.
Wow! Brilliant news and thanks for letting us know CobCottb.
we have sprayed the drive twice now with the soda crystals and it is turning yellow. has rained once since we sprayed. May have to spray one more time, but is a cheap solution. It seems to have worked best when it was wet, not as well on the places that were dry.
Same problem here in south west France. Gravel driveway, clay soil and have used a Roundup. Off to find the French equivalent of Dri Pak Fine Soda crystals. Cross fingers, please.
They're crossed.Let us know the results.
I found this thread with interest. I have the same problem in SW France where May/June weather has been horrendously wet. As far as I can see, soda crystals are sodium carbonate, which is the same compound as used for increasing pH in swimming pools - commonly labelled pH Plus In France. Anybody agree?
Yes it's sodium carbonate. What it's called in France I could not tell you.
It could be nostac. This is a bacteria (Cyanobacteria)that turns slimy after rain or exposure to water but driies is in sunshine.