Pond Boss Forums AQUATIC VEGETATION Controlling unwanted plants Hydrothol safe for fish if applied sparingly?

I have a 5 acre lake that I have allowed the Indiana pond weed to grow around the permitter based on the recommendation that it will be beneficial to keep the algae from growing so quickly. However, I have a beach area that I would like to keep clean and I'm wondering if Hydrothol would be ok to treat a 100' section with? I plan to have fish soon and have read that it can be toxic if applied heavily. But I certainly don't intend on using around my entire lake. Should I avoid it and just use the more expensive Aquathol?

Also, would granules be preferred over the liquid for this submerged pond weed?

Jadog, what weed is Indiana Pond Weed? Can you look up the scientific name? I need to know what the plant is before I can answer the question.

Try and find it either here: https://ag.purdue.edu/btny/purduewe...ying-and-Managing-Aquatic-Vegetation.pdf

or here:

https://aquaplant.tamu.edu/plant-identification/

Once I know what plant it actually is, I can give you the best treatment option.

Welcome to the forum! You are only a bit over 100 miles away.

Based on the second link you gave, I would say it looks most like Baby Pondweed (Potamogeton pusillus). Although a close second would be Bushy Pondweed (Southern Naiad). I don't think it's Sago. I took some images I took last summer which you can see in this post: https://forums.pondboss.com/ubbthreads.php?ubb=showflat&Main=42894&Number=559830#Post559830.

I agree, not Sago.

While it's not the answer you wanted to hear, (I don't buy into the "tell them what they want to hear" camp), you'd be better off using Aquathol K or Aquathol Super K especially if you aren't 100% sure of what it is.

Two reasons.

Aquathol is excellent for treating BOTH of those plants.

Aquathol isn't as toxic to fish as Hydrothol 191. With Hydrothol 191 you have to be careful of the dosage, AND you have to apply it from shoreline out to the center of the pond to avoid trapping fish between it and the shore. They need an escape route to get away from the herbicide.

That's fair. I don't actually have any fish yet but the Aquathol is not more than about 20% higher priced. So it sounds like that is the safer bet. Any experience on which which type you prefer? The Super K granules would certainly be easier to apply than mixing the liquid K formula in my tank sprayer. I can see the plants continue about 15 feet or so out from the beach and dock area. Even a hand sprayer won't get that far unless the wind is blowing to my back. And if I'm applying the granules, I'll have to throw it by the handfuls to get it that far. Or take out a kayak and apply it with a spreader. Any ideas from the more experienced?

Either from shore will be tough to get an even coverage without a boat. You need to apply it evenly over "X" area at "X" rate. One person in a kayak not being able to move the kayak while working the spreader makes it hard to get even coverage unless it's an electric or battery powered spreader.

I'd have to look up the label to see what the application rates are, but you need to follow what the directions on the label say to do for application rates.

I have a tank sprayer that I have in the boat, and I can use weighted lines on a boom to get the herbicide down to the plants while the boat is under motor power.

Using a weighted line on a boom sounds like a more complicated setup than just spreading from a motorized spreader. Is the K more cost effective than the Super K? Or why did you choose to do it that way? This stuff is pretty pricey so I want to make sure I buy the most appropriate option.

And it also looks like a surfactant is recommended. Can I use any non-ionic surfactant, or does it need to be one rated for aquatic use? I see that Alligare 90 is rated for aquatic use while others are not.

Aquathol K is a liquid concentrate soluble in water which is effective against a broad range of aquatic plants. Aquathol K has a wide margin of tolerance for fish and other aquatic animals.

For the plants that you say you have, you will need to apply 1.25 gallons of Aquathol K per acre foot of water to achieve a 2.0 ppm concentration. With the liquid, you use 1-2 fluid ounces of surfactant rated for aquatic use per gallon of tank mix. Cide-Kick, Cygnet Plus, Alligare 90.

Mix the correct amount of Aquathol K with enough water to get even coverage of the area that you want to spot treat, add surfactant to the tank once you know how many gallons you will need.

Aquathol Super K is a highly concentrated granular form of Aquathol. It is for use in ponds and lakes. It has been shown to be effective against a broad range of aquatic plants.

Apply 13.2-22.0 pounds of Aquathol Super K per acre foot to the area that you want to spot treat. It should be applied evenly across the surface of the water of the whole area that you want to treat.

I have an easier time applying the liquid than the granular. I don't have to worry about what direction I move the boat in (with the granular I don't want to be driving through the dist that the particles may leave in the air) and I can dilute the liquid so I get even coverage, even covering the area going back and forth, then going 90° to the area that I just covered to get even coverage. You don't need a surfactant with the granules.

It all depends on what YOU as the applicator is more comfortable with.

An acre foot of water is 1 acre (approx 208'x208'), 12" deep or 325,851 gallons of water.

So from my calculations, an area of 80' by 20' (1600 sq ft) at 4' deep would need 1.28lbs of Aquathol Super K. This can be calculated as (application rate in ppm) x (average depth in feet) x (0.16). The .16 is for 1600 square feet. The PPM is 2.0.

2.0 x 4.0 x 0.16 = 1.28 pounds for 1600 sq feet at 4' deep

That would give me about 7.8 times from a 10lb bag of Super K.

The Aquathol K liquid on the other hand offers significantly more value and would require about 24oz per 1600 sq feet at 4' deep. I calculated this based on the SDS label which shows the ppm rate at 3.8 oz per 1000sq feet.

So to calculate 1600 sq ft I used the following:

(3.8 / 1000) * 1600 = 6.08 oz per square foot. Then multiply this by the depth of 4'. This totals 24.32 oz at a 4ft depth for 1600 sq ft.

A 2.5 Gallon jug would be 320 oz which would allow me to treat more than 13 times. The liquid is also less costly so I figure it would be nearly half the price to apply the liquid as opposed to the crystals.

Unfortunately, I have no boat to sit in and inject the liquid below the surface as you suggested. I suppose I could get a canoe but I don't really have a place to store a boat. I could get some waders and wad in with a backpack sprayer. Otherwise, it seems like the crystals may be my best option?

One of my friends has a lake the same size as mine (5 acres) and he told me that once a year in May, he pours 2.5 gallons of Aquathol (half on each side) into his pond and treats the rest with 2.5 gallons of Tribune (I think that's just Diquat) and roundup. He told me that's enough to treat all of the submerged weeds in the lake. I thought that seemed like way to little to do anything and was the amount for maybe 1/2 acre.

Take your depth reading at the deepest part of the treated area (if going back to shore) and divide it by 2 to get a close guesstimate on average depth.

Pouring it in like he does may work for him, but it makes the pour point way high ppm wise. If he were to do that with Hydrothol 191, I can almost guarantee you he'd be killing some fish.

Unless you are worried about the boat getting feet and walking off, lots of pond owners have a small jon boat at the pond upside down on shore. Small like 10'-12' in length.

Any chance you can easily pull down your lake a few feet to make it easier to treat?

Might also do some dock repairs, add more structure, etc. at the same time.

I would say the deepest part to be treated wouldn't be more than 6'. So probably 3' depth could be used. I'm going to add some additional dye soon which I expect to help prevent future growth and that depth could become less. I could also rake it to remove a lot of the weeds, but I don't think it will get the roots. Should I apply the treatment first and wait for it to begin dying before I rake?

As for the boat, my wife doesn't care for the look of having a john boat on our beach. Our lake is new enough that it isn't even full yet. It is going on the third year of filling, so it's quite slow.

If I spray on the surface of the water instead of injecting, that won't be nearly as effective, correct? I could use an inflatable boat or our floating foam raft too and just hold the spray wand down below the surface. Seems like there may be a science to this. Thanks for talking me through it.

Apply the herbicide before raking, wait until it is dying before raking. You want to kill the roots. Get a camo tarp and throw it over it, stick some branches in it and tell honey that it's a big bush. LOL

I wouldn't be in the water when I'm spraying but that's just me. The closer to the plant the herbicide is put in the water the better it will work.

Great advice. And much appreciated. Good thought on making my own bush too. Although the branches dying in a week would probably give it away

Maybe a trip to Hobby Lobby is in order? LOL