Pond Boss Forums AQUATIC VEGETATION Controlling unwanted plants Safe use of Hydrothol 191

Got a problem with Sago Pondweed and Small Pondweed (Potomogeton Pussilus) in my largest pond. And then there's the Chara which is quite extensive. I'd say a good 60 percent of my pond is being taken over by large beds of the two pondweed species. And Chara covers 99 percent of the bottom up to a couple of feet deep. Manual control is just too labor intensive although I have tried it. From my research granular Hydrothol 191 is the herbicide of choice and I should spot treat gradually moving around the pond as the previous are becomes nontoxic.

However it says it can be toxic to fish and of course I don't want to treat the whole pond at once anyway, which not only would be toxic to the fish but create serioius oxygen demand.

Anyone know of any guidelines of how large an area I can treat at at time? I seem to have read somewhere the fish will leave an area if I only spot treat. So as long as they have an area that is free of the herbicide I should be fine.

Thoughts?

Try this - similar but for pond use.

http://plants.ifas.ufl.edu/guide/aquatholsuperk_label.pdf

Here is the other if you want to use it.

http://plants.ifas.ufl.edu/guide/hydrotholgran_label.pdf

Thanks Eric! I saw this but it's good informaton. I think I'm going to try in in a very small area sparingly to see how much is needed to be effective and then go from there.

Looks like I should try and stay below .3 ppm.

Just be careful with hydrothol. you dont want to touch it at all and it has about a weeks worth of restrictions with it.

No problem. I use rubber gloves when handling it. It doesn't seem to be working as fast as I thought it would. Been three days and I see no difference.

Anyone have any ideas when it's safe to move on to another 1/10th of the pond? From the information I've read it's pretty much gone in 7 days. I'm wondering if I have to wait 7 days to apply in a different 1/10th of the pond.

So far the Hydrothol 191 had NO EFFECT on the pondweed or the Chara. I have been increasing the amount cautiously in my spot treatments but so far no effect. Even the fish don't seem bothered by it.

I'm thinking the thick Chara on the bottom is absorbing it which prevents the pond weed that is inbedded in it to be effected.

Cecil -- I think you know that I don't do much vegetation control. However, Chara is an algae, and not controlled by the hydrothol? However, it certainly should have gotten the pondweed.

Dave,

The Hydrothol has finally knocked down the pondweed I treated. Apparently it just took longer. Bill Cody seems to think since my water is almost off the charts on hardness, that may inhibit not only copper products, but also the Hydrothol.

As far as Chara being an algae, that is of course absolutely true. However Hydrothol is supposed to control algae also, and Chara is on the list of vegetation controlled (at least in the Stoney Creek Equip. Company catalog I ordered it from). I did try some on bottom growing filamentous and it does work on that and stat. Much better than the copper products I have used (Cutrine plus) which are absolutely worthless in my hard water.

One thing I like about Hydrothol, as even though it could be toxic to fish, if one gets carried away with it and treats too much of a pond, it leaves no residue or heavy metals like the copper products. It's even supposed to be safe for trout in very small quantities although I have not tried it in my trout pond, and would be hesitant to do so.

Yeah, I figured when I posted this that you already knew what I was saying. I rely on a good publication from the SRAC that lists hydrothol as excellent for pondweed control, but only good (hydrothol) and poor (aquathol) for Chara. Those rankings always made me sort of suspicious. I'll email a copy to you.

Just like fertilizing, I'm really leery of plant control up north (oxygen depletion). So, I usually have people try the granular hydrothol/aquathol just trying for spot treatment (as you mentioned). So, I'm glad to hear some gradual results on the pondweed.

Glad to hear your full story. We deal almost exclusively with hard water.

Someone else asked about this publication. Here is a web link. Click on SRAC 361 Aquatic Weed Management: Herbicides.

http://srac.tamu.edu/index.cfm?catid=15