Pond Boss Forums AQUATIC VEGETATION Controlling unwanted plants Curly-Leaf Pondweed

I have a small 1/4 acre pond that is being taken over by curly-leaf pondweed. This is the first time in 10 years I've seen this weed but it's spreading fast. We have three grass carp in the pond but they don't seem to be eating it.

Is there any way to control it without chemicals?

My curly leaf pondweed was almost completely eliminated after introducing papershell crayfish, but I am not sure where to source them anymore. It is impossible to rule out some other factor in the weed control, but I do not know what other factor could have been responsible.

Drogo, a low dose of Sonar AS (Fluridone) will kill it and won't harm any other plants in the pond (with the exception of Eurasian Watermilfoil).

Sonar AS is $250 for just 8 oz.....pretty much out of my price range. Especially if it doesn't work in one application.

And I found a place that sells papershell crayfish....in upstate NY. But they only deliver in NY. So being in Indiana.....

Guess I'll be out there manually pulling it out.

maybe some of the other brands of fluridone are a little less? Look up wipeout.

Can Curly leaf pondweed be killed only in certain sections of a pond and left elsewhere?

I have a 2.3 acre neighborhood pond that we have been having professionally treated yearly for The curly leaf pondweed and for algae. (Cost: $2300)

The spring treatment does kill off the pond weed for that year, but killing all the pond weed means the algae goes nuts (since no other plants to consume the nutrients) which means the company has to spray multiple times a year for algae and the water generally looks cloudy and gross.

So I’m wondering if I could just treat on my own by spraying parts of the pond for the curly pond weed (like shorelines) and leaving other areas (center of the pond (weeds grow even there because pond is only 6’ deep or so) for the pond weed to still grow and maybe get somewhat of a balance and not have the algae blooms. Thoughts?

ZTrain - There are granular aquatic herbicide brands including 2-4D formulations that can be used for spot treatments by just spreading the correct amount of product in a specified area. I and others here have also used liquid diquat brands such as Reward and Harvester that are likely what are used by the 'professional' applicators that are hired by the HOA. These liquid formulations can be used as spot treatments by injecting the mixed solutions underwater into areas with curly leaf for good results in sections of a pond. Good injection methods and even coverage into treatment areas are important for best results.

If the curly leaf in your pond seems to returning as abundant or more of growths each successive year then IMO the professionals are not applying the herbicide early enough in the life cycle of curly leaf. Chem-kills for curly leaf should be applied before the plants form turions and seeds. Turions and seeds are how the plants repopulate the pond each year. Good effective efforts of annual kills each year should gradually over time reduce the amount of redevelopment of curly leaf that appear each year.

^^^ What Bill said above. You want to apply the chemical in late May at the latest. You could treat the pond once for algae around the beginning of June when the water temp is in the low 60°F range then within a few days stock 100# of Tilapia TIlapia. That will take care of 90+% of the algae the rest of the year too. We stock a bunch of Tilapia for algae control, where in the state are you?

Thank you both for the good info!

I’m in central Indiana. East of Indianapolis.

My suspicion as to why the curly leaf comes back each year despite the treatments is that the neighborhood has several ponds, and there are drainage pipes that I believe run between them to some extent. I’m guessing one or more of the inflow pipes reintroduce the weeds from other ponds.

Also possible, the treatment company doesn’t want to fully kill the weeds because they want to keep getting the $900 a year for that treatment. 😂

This past year due to some confusion between HOA and the treatment company, the treatments didn’t start until later in the year than normal, after the curly leaf had grown quite a bit. The thing I noticed was that the water quality at that time seemed so much nicer than it normally is. Water was clear, the fish seemed to be thriving. My suspicion is that because the plants were allowed to grow, rather than being wiped out early as they had been in the past, they were absorbing enough of the nutrients to keep the pond clear and healthy. After treatments to kill off the weeds it ruturned to its normal cloudy appearance for most of the year.

That’s why I was considering leaving some areas of the curly leaf, to try to get a more balanced pond and better water quality, but I just didn’t know if that would be a bad idea and just lead to more issues.

ZTrain - I agree with your conclusions about the relationship of pond water clarity, CPW abundance and weed treatments. Frequently when CPW is abundant the water has fewer dissolved nutrients, dissolved solids precipitates will often accumulate on CPW leaves and filamentous algae is often at low abundance and low density. IMO the amount of CPW needed to produce clear water is highly dependent on the nutrients in the pond (eutrophic nature). My experience is the more CPW preset the clearer the water becomes.

ZTrain,

Establishing other plants that don't spread as much as the CPW might also help your pond.

There are several aquatic plants, and even some emergent shore plants, that will take up some of the nutrients that would otherwise go to the FA.

Further, if you could establish some beneficial bottom-rooted aquatic plants in some areas, that might make if more difficult for the CPW to propagate in those areas.

I cannot speak to others situations, but introducing papershell crayfish solved my issue with curly-leaf pondweed.

Good idea, RAH.

His fish might even enjoy the addition of the papershell crayfish!

I can't remember, were your crayfish extirpated from your pond after they cleared out their CPW cover, or did you have enough rocks for them to maintain a sustaining population?

I am not sure if the crayfish are still there, but I suspect they were not completely wiped out. I do have a rip rap jetty for cover. Still no problem with pondweed though.

My pond is pretty much all muck bottom so I wouldn’t think crayfish would do particularly well.

One additional question, would putting some lilies in the pond (potted) be a bad idea? Would they spread? Id like to have some lily pads but don’t want them to take over.

While my water lilies are planted in the pond bottom, folks say that planting them in pots typically keeps them contained. There are many varieties with differing levels of vigor and size. I think that most crayfish species like rock rather than mud?

Reviving this thread as it looks like I AM going to try to self treat my pond. So for treating some but not all of the pond for curly pond weed, would a granular herbicide be better, or Diquat? I had looked at Diquat and was thinking I could spray it with just a garden type sprayer, but maybe that’s not a good idea? You mentioned needing to inject it into the water.

If granular is best, can you recommend a brand, and what’s the best dispersal method for that?

Best herbicide to use is Fluridone. A 10 PPB dosage is all that is needed. Mix with a few gallons of water, pour it into the pond, walk away.

That is as long as the pond doesn't have water flowing into and out of it for the next 30-45 days.

EVERYTHING else that you use will also whack native plants that you might want to save. A 10 PPB dose of Fluridone won't.

BUT the downside is you cannot spot treat with it. You can spot treat with granular 2,4-D or liquid DIquat. BUT if the other home owners do the same thing, you will be back to having the FA problem.

If you are in a state that allows Tilapia, stock them after you treat the algae (water temp 65°F or higher). That will take care of the FA problem for the year (or it should).

Ok. Thanks! Yeah, since I want to try to kill only part of the weeds I think I’ll try Diquat and see how it goes.

I’m in central Indiana. I see you’re in Indiana as well. Do you know where Tilapia can be purchased in central Indiana by chance?

Aquathol super K and hydrothol are options for the curly leaf . maybe not as good as floridone but less expensive.

We will be running around stocking Tilapia in 3-4 weeks. We are about 30 miles S of South Bend, but we stock all over the place.

I’m going to treat with Diquat and Cutrine plus. I’m not clear based on what I’ve read if I need to also add a surfactant to the mix as well? Is it necessary if surface spraying the pond?

I’ve been searching around the internet and I still can’t get a good understanding of whether I need to add a surfactant to the Diquat mix for treating submerged weeds. (Or in my case now, Submerged weeds that have reached the surface in some cases). Or if so, how much to use. Most things I read seem to indicate that it is needed for emergent weeds, but unclear for submerged.

It helps, but it's not necessary if you are using a fluridone based product. (that's what I prefer to use for it). 1 fl. oz. surfactant per gallon of tank mix is sufficient. Use a surfactant that is rated for pond use, NOT one for terrestrial use or dish soap.