In April 2024, while pulling my canoe after a mostly unsuccessful day, I ran into a few environmental scientists that were curious about water levels and asked if I'd been out a lot recently. "We take it the river has fallen a lot over the last week," one posited. "Oh yeah," I replied, "quite a few feet". "Yeah, we're not always used to seeing the species we're surveying for six feet up in the trees." he said. These scientists were from a team working with the Army Corps of Engineers, and the species they were surveying for was a highly invasive aquatic plant called hydrilla. Hydrilla's presence in the Connecticut river is relatively new, with first confirmation coming in 2016 in Glastonbury. It is especially noxious, because any time a piece is broken off, it can sprout new roots and make a new plant. This makes it uniquely hard to control as manual removal is not longer an option once density reaches full blown infestation. Control is important, both ecologically and socially, because hydrilla is so prone to rapid spread that it has significant negative impacts on water quality, fish, native aquatic plants, and outdoor recreation like boating and swimming. So control in some form or function is paramount. And this crew was doing preliminary study for herbicide treatment. Work has been done for a number of years studying both the plant itself, monitoring it's spread, and testing possible methods of mitigation and control. This new project sought to determine the efficacy of herbicidal treatments, and the water body I was leaving was to be one of the first test sites on the first year. One of the herbicides in question is called Diquat, and though it's use and application at one site went without major public backlash in 2024, the same cannot be said for 2025.
FOX61 interviewed protesters they described as "environmental activists" at the state capital as they voiced their concerns on the use of Diquat. One of those interviewed was Selina Rifkin, whose sentiment isn't an uncommon one currently "Spraying horrible chemicals that kill everything into our lakes and rivers. It isn't necessary." A Change.org petition headed by a photo of a handful of dead, floating fish, evidently European species- it looked like crucian and barbel to me -got the messengers point across. Diquat is going to kill everything, these folks firmly believe that. If this were true, there'd certainly be reason to protest it. How could the Army Corps so brazenly poison out waters, and why would CT DEEP sign off on it?
Way back before I ever put pen to paper about fishing, or knew almost anything at all, my best friend and I dumped a bucket of Diquat is his farm pond. I kid you not, I have real world experience with this poison that kills everything. Young, dumb, and frustrated with summer weeds making it hard to fish the pond the way we wanted to, we sought weed control as a way to better our fishing. His dad got is a big ol' container of Diquat. We read the directions, didn't wear any safety gear of any sort, and did our best to distribute the whole jug's worth across the tiny bass pond. Memory serves me that it did kill off a fair bit of the heavy vegetation, and to our untrained young eyes, nothing else. There certainly was no fish kill, the pond still to this day is loaded with bass, sunfish, bullheads, and all of the wonderful creepy crawlies that those fish eat. We also didn't die, despite definitively doing it all wrong. Hearing and reading a lot of comments about this same herbicide "killing everything" seemed a tad strange. Of course, my experience is anecdotal at best, though perhaps of higher value than much of the commentary currently circulating because at least I have some actual first hand experience... but that isn't enough, not for me. So let's dig into everything we can, shall we? Let's start with the basics. How does this Diquat stuff work?
Diquat is short for diquat dibromide, or 6,7-dihydrodipyrido (1,2-a:2',1'-c) pyrazinediium dibromide. Now that sounds scary... but I'm not a chemist, and if it sounds scary so might this: β-D-galactopyranosyl-(1→4)-D-glucose. That's lactose, that's in natural milk... not scary at all, you just aren't a chemist, most likely. Chemicals always sound scary if you aren't hugely familiar with chemistry and reading chemical formulas. That's fine, neither am I, but we're going to have get a little cozy with chemistry here to understand what 6,7-dihydrodipyrido (1,2-a:2',1'-c) pyrazinediium dibromide does. Basically, it binds to photosynthesizing cells and inhibits that key processes of plant function- turning sunlight into energy. The chemical accepts electrons from Photosystem I, one of a plant cell's two photosynthetic systems. That electron is used to create a reactive oxygen species (ROS), which damages the cell and prevents NADPH and ATP production by that cell. NADPH helps make glucose, lipids, and nucleic acid, and ATP provides energy. It also destroys the cell membrane. Without these things, the cell dies. And when all of an aquatic plant's photosynthesizing cells die, it dies. That's how Diquat kills hydrilla and other plants. It than binds with particles of soil and sediment, usually leaving the water column free of detectable levels within a day or two, though it remains undegraded in sediment indefinitely.¹ Diquat is also used as a desiccant on potato crops and some seed crops used for feed. A desiccant, if you aren't familiar, is something used to dry things out or keep them dry.
It is entirely reasonable to have concerns about how a chemical compound that completely kills a photosynthetic cell might effect other cells, including outs and the species we care about. This is especially true given that Diquat is banned by many countries and the European Union (many of the people I've seen bringing that point up are also the sort to suggest that the European Union is an overbearing, freedom less hell-scape, so that comes off as a little rich. Sorry, I call it like I see it... you can't have this both ways). Let's start with humans, since we tend to be a selfish lot....
A 63 year old landscaper in Florida admitted himself to the hospital about 90 minutes after drinking a gulp of herbicide from a Gatorade bottle. He would die soon after from multi organ failure. The medical professionals involved in his case did a brief case study highlighting it, as well as the need for further study on diquat poisoning. It doesn't read pleasantly. Upon admission, he was having uncontrollable urination, diarrhea and gastric emesis. By his fourth and final day is the hospital, effects had reached his brain. "On day four of hospitalization, the patient was noted to have new onset dilated pupils and was taken to receive a CT scan of his brain, which showed diffuse cerebral edema and toxic encephalopathy with cerebellar tonsillar herniation and mild hydrocephalus." ² Basically, in the body, the ROS previously mentioned makes hydrogen peroxide. Normally the body detoxifies hydrogen peroxide, but this reaction from the Diquat cycles over and over, overwhelming any chance of that. The case study notes that Diquat poisoning is quite rare, hence the need for further study it sites only 30 cases from 1969 to 1999 with a 43% mortality rate. It also sites that nearly all similar cases in which more than 12 grams of Diquat were consumed result in death within a few days. The same ROS that causes a photosynthetic cell to die leads to multi organ failure. Scared now? It's important to consider concentration. Of course, drinking a full gulp an herbicide that makes a reactive oxygen species and spurs cellular havoc is a potentially deadly proposition. So far no study I can find indicates health risks from exposure to a water body treated with diquat within just a few days of treatment, and that comes down to Diquat's affinity for organic molecules. After dispersion in a water body, it binds with with plant cells it kills, but also with tons of organic particles in the water column and in the sediment on the bottom. It becomes a more or less inert there, no longer present in the water column and allowing aquatic plants (hopefully the native ones, replacing the invasives killed by the diquat) to grow unabated. This is what I watched happen in that pond all those years ago. There was no noticeable evidence of a herbicide in the water just a short time after treatment. Sunlight also degrades diquat based on numerous studies, one citing a photodecomposition half-life of 1.6 weeks.³ So, without too much time passing, the science says there shouldn't be much to worry about so far as swimming, contact with the water, or consuming fish goes. Diquat is dispersed at low comcentrations compated to the fatal dose and is largely undetectable in just days. It isn't recommended to drink water treated with diquat within three days, but, speaking as someone on and around it all the time, you don't want to drink from these Connecticut River backwaters anyway. It might kill you on a good day, Diquat or not.
Onto other species... that Wisconsin DNR fact sheet makes mention of study on fish, all very Wisconsin. Walleye showed signs of poisoning when contained in diquat treated water, other game and panfish did not. Some fish kills have been recorded in diquat treated waters, especially small ponds. This is most likely a result of oxygenation, as rapid vegetation death and decomposition can use a lot of dissolved oxygen. This shouldn't be a significant problem in the Connecticut, where tides cause a significant amount of water exchange day in and day out. The bigger problem comes with macroinvertebrates, which are indeed vitally important. The same fact sheet states "...certain species of important aquatic food chain organisms such as amphipods and Daphnia (water fleas) can be adversely affected at label application rates." The Army Corps project isn't dismissive of the potential impacts on wildlife, as anyone who cares to sit and read available drafts and proposals for this project can find. Pretty plainly though, labeling Diquat a "poison that kills everything" is more than misleading... its just plain wrong. There is validity for concern with both human and environmental impacts, but most of the posts making the rounds on social media lack rigorous research, citations, or anything that would make them trustworthy. And that's just where the problems start.
That same environmental activist interview by FOX61 than I mentioned earlier, Selina Rifkin, later on said "There could have been an educational campaign about what this is. There could have been a call for volunteers to pull it out by hand. There could have been some kind of examination of the other possibilities for getting rid of it is, this is, this is a financial option, and it's the easy solution." This is the point where I must admit, I get a little bit pissed off and say... are you kidding me? Every single thing she lists there has been done already, it takes just seconds to find that it has been done, and if anyone actually cares one iota about this issue these words wouldn't leave their mouth. There's a sign at just aviation every launch and put in on the lower Connecticut that tells me what Hydrilla is, how to prevent the spread, and has a nice little picture of what it looks like. The education is there. The Connecticut Rover Conservancy regularly holds manual water chestnuts pulls funded in part by grant money from the state's AIS program I've already written about that. The volunteer effort is available. Information on why manual removal can in fact worsen hydrilla is immediately readily available with a Google search. Manual removal alone will not work. And this entire Army Corps hydrilla project has been about finding the best option to control the hydrilla through multiple means (read here). CT DEEP has also been exploring management options since at least 2021. In hours of research prior to and while working on this cursed blog post that I shouldn't have to write, I found sourse after source after source that partially or wholly refutes every argument being made by the Jonny-come-lately diquat protestors. We are a lazy, triggerable, reactive society that absolutely fails to find the forest through the trees time and time again. I'm not even here to say there isn't some merit to suggesting diquat shouldn't be used, I'm not convinced that it will be an effective treatment on its own. But it also doesn't take much research to make sense of this Army Corps project, why it's underway, and why they're using Diquat on a limited number of waters. Unfortunately, if you've made it this far, I doubt you're the sort that is causing this outrage. If you are though, thank you for sticking around. Please, go to your next argument, make your next comment, attend your next protest, or donate to your next cause armed with legitimate arguments instead of reactionary social media posts. Spend some time researching the topic with actual doctors, scientific papers, and as many different sources as possible.
Media (both social and mainstream news) failed us on this one, as it has in the past and will continue to in the future. Facebook and Instagram made it easy for people to pass along inaccurate posts. FOX61 and others did a poor job of pointing out inaccuracies in the demonstrator's statements. A petition circled with a blatantly fear-mongering header image, with thousands of signatures and counting. I'm sick and tired of this; if all of these people could have put this energy and effort into being informed and taking action on invasive species, there'd be no need at all to apply herbicide on the Connecticut River. But here we are, fighting a government that's desperately trying to undue the problems we cause, then complain about, then complain about the potential solutions to, then complain about the cost of. It's all very tiring. I have very little hope anymore, but if so many as one person walks away from reading this less inclined to hop on the disinformation train, I guess I've done my part. Read as is spoken through clenched teeth while smashing my mouse to smithereens against my desk: Now its time for me to go clean, drain, and dry the canoe after another day of pulling water chestnuts on the big river, trying to beat a problem that could one day hit me right in the wallet the same way hydrilla has been.
Currently, the Diquat treatment has been postponed till 2026, reportedly for funding issues.
¹ Wisconsin Department of Natural Resources, 2012. Diquat Chemical Fact Sheet,
² Daniel M Aloise, Adam Memon, Ana Zaldiver. 2022. Diquat Herbicide Organophosphate Poisoning and Multi-Organ Failure: A Case Report
³ Smith, A.E. and Grove, J. 1969. Photochemical degradation of diquat in dilute aqueous solution and on silica gel. J. Agric Food Chem. 17:609-613.
https://www.nae.usace.army.mil/Missions/Projects-Topics/Connecticut-River-Hydrilla/
Video overview of Florida landscaper case: https://www.youtube.com/watch?v=Xmu48JYFTBc
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