Can anyone tell me the effects of a herbicide called Karmex on widgeon grass and water primrose?

Karmex is not labeled for use on aquatic vegetation. Old-timers tell all sorts of horror tales about the misuse of Karmex and grim results that followed . . . dead trees, fish-kills, the works.

Mark McDonald
Editor, Pond Boss

Bill - I'd really like to know WHO is promoting the use of Karmex for aquatic treatments!!! Besides misleading good folks like yourself, that person is also violating Federal law as well as providing another point of attack for the anti-pesticide factions (via product misuse). Take a guess at the biggest reason why Dursban is no longer available to the retail market....
Do yourself a big favor and direct your questions (and business) to a chemical dealer who isn't proposing that you use Karmex in your pond.
BTW: I sell Karmex (diuron), but will absolutely refuse to sell it to anyone who indicates that their intended use of the product is related to pond treatments.

Most of the people that contact me with pond problems AFTER using Karmex tell me they got it at their local farm and ranch center, coop, etc. My experience with employees at Coops is that they are very knowledgeable about ag related stuff, but know very little or nothing about aquatic vegetation management. I would certainly advise anyone planning to treat vegetation in their lake to ask somebody who specializes in aquatic vegetation. Kudo's to Mr. Duffy for his input on this board.

Kelly, this was a product name given to Marshell Williams by a feed center. He was at my place last weekend and I told him he had better get advise on the use of this product before doing anything. I posed the question for him and by now he has probably seen the response. Everything is well in my pond with the exception of declining water level. RAIN!!!!!!!!!!

Hope Marshell doesn't mind, but here's an email exchange from today to wrap up this thread.
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Marshell here.... I am the one inquiring about karmex..... I just bought this property and it has two ponds.... And old farmer came by and mentioned karmex... then I went to *-* Feed in Magnolia, Texas and the owner said "oh, sure,,,that is the only reason we sell karmex, is for killing moss in ponds,,,good stuff"
I appreciate the input, and I will not use this stuff at all.
Tell me what I can use to cut back on this stuff
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Marshell,
Thanks for the info. It is a shame that people who profess to have respect for and "knowledge" of pesticides, their environmental-impact and the law think themselves smugly-wise to recommend such treatments. They have no idea what they're doing - especially to their customer's pond and its future fish-productivity.
Unfortunately, KARMEX continues to be illegally and inappropriately utilized for aquatic treatments because it DOES kill algae; all kinds - including ALL planktonic algae (the base of the pond's foodchain), as well as nearby trees, grasses and virtually any other plant or algal specie. It also collects in fish-tissue and has reportedly caused F1 genetic mutations in some fish offspring.
Dr. Jim Davis (former Fisheries Specialist at A&M) frequently commented that more fish have been accidentally killed by Karmex (diuron) than any other pesticide on the market - typically due to massive oxygen crashes that occur after the
product is applied to an algae-infested pond (caused by the decomposing algae).
I wished a had an simple, easy, cheap, safe and legal answer for dealing with algae in ponds. But, unfortunately, it doesn't really exist. Basically, the only answer lies in a management program that begins early in the spring - long
before filamentous algae makes its presence offensively known.
In a nutshell, make every effort to maintain a plankton bloom (which serves to reduce sunlight penetration, while also benefiting your pond's
food chain). This simple act will greatly help to reduce the severity of future filamentous algae problems. Second, treat shoreline patches and growths of filamentous algae - if necessary - with HYDROTHOL 191 (endothol) or a chelated copper product (such as CUTRINE PLUS, CAPTAIN, etc.). Such treatments will likely be needed every few weeks along the shoreline. But, if done correctly and in a timely manner, the expense isn't too great - and your fish population should not suffer any negative consequences.
Hope this helps.
Regards,
Kelly Duffie

News Flash: Just received a call from a fellow (who isn't a PB reader) wondering why his fish were all dying shortly after a KARMEX treatment.
After explaining the cause, I suggested that he have a formal visit with the person who recommended the treatment - since that person (a feed store) may now bear partial responsibility for the cost of restocking the pond (since the recommendation violated the product's label).
Bear in mind, the product ISN'T at fault. Rather, it was the improper (and illegal) manner in which it was recommended & used that caused the problem.