Cumbungi and spike rush are two of the worst weeds you can have in your dam. They’re persistent, fast-growing, and nearly impossible to pull out once they get big enough. Cutting and spraying with herbicide can be effective — if time-consuming — solutions, but the best way to deal with cumbungi and spike rush is by getting to it early.
Summary
How to Remove Cumbungi and Spike Rush from Your Dam
We want to talk to you about cumbungi and spike rush. These are quite simply two of the worst weeds you can get in a dam.
Let’s discuss why they’re such a big problem and what you can do to remove and control them.
Cumbungi and Spike Rush: Two of the Worst Weeds You Can Get
Cumbungi and spike rush are the two worst emergent weeds — the type of weeds that grow up from the bottom and come up above the water. Cumbungi is also known as cattail in the US. Here in Australia, it might be called cigar rush or bull rush, too.
It looks somewhat like a cat’s tail or a cigar, which is why they get that name. It’s so invasive because these flowers or seed pods turn into something like fairy floss, and then blow everywhere in the wind.
They spread so quickly through a dam and into neighbouring properties as well.
Spike rush is also highly problematic. It’ll overrun a dam quite quickly. It’s somewhat hollow on the inside.
Both cumbungi and spike rush are near impossible to try and pull out once they’re bigger. If they get into your dam, they can be a nightmare.
In clear water, you see them growing up to a couple of metres deep. So if you’ve got a shallow dam and these weeds come in, you want to deal with them really quickly before they end up choking the whole system.
And they will completely choke a whole dam — they can turn it from an open water body into a swamp.
How to Control Cumbungi and Spike Rush
Whether it’s for cumbungi or spike rush, control methods are similar. If you get there fast enough and the weeds are young enough, you can try to pull them out. If you want to take that approach, be vigilant — if they get too big, you won’t be able to pull them out.
Cutting
If you don’t catch them early enough, your options are cutting them out with brush cutters. You just go through and cut them out. If you use the cutting method, you’re going to get reshoots quite quickly — you’ll have a battle going on for potentially a few years while you cut, get regrowth, cut, get regrowth, cut, get regrowth. That’s just the process.
Cumbungi especially has a large root mass that will go through an entire dam, so you’ve got energy stores in that root mass. When you cut it, it shoots up new growth. So you keep cutting and cutting — ideally below the water level — and eventually, its energy reserves drop off and you’ll finally win the battle. But it’s a long process. It’s essentially the same process for spike rush.
Spraying
Another option is spraying. You can spray the cumbungi or spike rush with an aquatically registered herbicide, and the plant will die off. It’s simple, but there’s a problem — when you spray these types of weeds, they don’t actually fall down. You spray, they go from green to brown, but they’re still there, standing upright. You still have to go through and cut down the weeds.
Cut & Spray
One option is to combine cutting and spraying. You can take two approaches for this. First, you can spray first, cut it down, and spray any regrowth. Or you can cut it first and then spray regrowth. It doesn’t matter.
Physical Solutions
If you don’t want to cut or spray, you can consider physical products like a Lake Bottom Blanket. These are mats that you can use to smother the weeds by physically covering them and blocking sunlight from reaching them. What you do here is cut the weeds to below the water level, then cover them with these specialised tarps to stop sunlight from reaching the plant.
You leave that there for potentially months to completely starve the plant, and kill it off slowly.
Excavation
If your dam has been neglected and it’s in pretty bad shape — enough that it’s holding virtually no water — you can consider excavation. If the other methods are pointless because you need to do work on the dam anyway, this is actually the best method.
You get an excavator in to scrape out the weeds and everything else. If you have a larger dam you’ll need a long-reach excavator with a good operator, but you can get a lot of the problem this way. Then you can go in, cut, spray, and smother to get everything nice and healthy again.
If you’re working on a dam this way, you do need to be careful you don’t go too deep and penetrate the clay. But if the situation gets this bad, excavation is a good solution.
Prevention is Better Than Cure
You’re always better off to be vigilant and get cumbungi and spike rush immediately when you first see them popping up. Just get in there and get them out as best you can. If the problem gets too big, you won’t have a dam anymore — you’ll have a swamp. Preventing it from getting to the point where you’ve got to resort to harsh, extreme treatments is the number one thing you should do to manage cumbungi and spike rush.
Look for long-term management and treatment options like aeration and biological control methods like Biostim. Aeration can help create the conditions necessary for aerobic bacteria, which are excellent at dealing with weeds and algae by outcompeting them for nutrients. Products in the Biostim range can boost these bacteria further, directly deal with nutrient-rich sludge at the bottom of your dam, and even bind essential nutrients like phosphorus so that they can’t be used for growth.
The best way to control cumbungi and spike rush is by managing your water so they don’t get the opportunity to thrive in the first place. And when you do see them, be ruthless.
Want to Know More?
Get in touch with us. We offer FREE expert advice, perform site assessments, and can supply you with practical, effective treatments to improve your water quality and control persistent pests like cumbungi and spike rush.
