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The Story of Formula 409©

I recently had the opportunity to visit with a number of guides, outfitters and fly shop owners from around the country and all of them expressed concern about invasive species. Unfortunately, one of the most common responses to the problem I heard about was some variation of how they are making sure to be clean using Formula 409© to disinfect their boots and gear. Many of these fly fishing professionals are very dedicated in their use of Formula 409© and several business owners told me that they require all of their guides to carry spray bottles of the disinfectant. 

While it was great to see the commitment that these people have to protecting the resource, the reality is they are wasting their time. The use of Formula 409© is what I consider to be a fly fishing urban legend. That is, a story that is continually spread because it carries enough significance that it motivates the fishing community to preserve and propagate it. We all want to believe that there is a chemical spray we can use on our gear to prevent the spread of invasives and Formula 409© has firmly established itself in many people’s minds as being just that. Unfortunately, it’s just not true.

How did we get to this point, where many people believe and preach an action that is not effective? The answer is simple. It starts with a basis in scientific discovery followed by misinterpretation by a concerned and vocal fishing community who aggressively spread the false information in the belief that they are helping to protect the resource. Let’s take a closer look at how we ever got onto Formula 409© as a gear disinfectant. 

The study that brought public attention to the use of Formula 409© was conducted in 2005 by the California Department of Fish and Game (CDFG). At that time, New Zealand mud snails (NZMS) were a new invader spreading rapidly across the West and were first being reported in California. It was suspected that NZMS would cause a significant ecological damage and would likely impact on trout population levels.

In order to reduce the chances that the fishermen were spreading CDFG conducted both lab and field studies to determine if there were ways to disinfect waders that were exposed to the snails. They tested a variety of chemicals and the determined that a 50% concentration of Formula 409© was one of the best choices for killing snails on waders and boots. The full details of their study were presented in the report Controlling the Spread of New Zealand Mud Snails on Wading Gear. 

The news that CDFG said that Formula 409© would disinfect wading gear spread rapidly through the fishing community. Many anglers began to carry spray bottles and have become religious about cleaning their boots with Formula 409© after each trip. Unfortunately, from the very beginning, anglers failed to understand that the measures needed to disinfect boots using Formula 409© went far beyond just spraying the boots.

The first problem for the average angler is that the disinfection method used in the CDFG experiments were never adequately communicated by the fishing community. The CDFG Formula 409© experiments were conducted by taking boots and sealing them in a waterproof bag along with 2 – 2 ½ gallons of 50% Formula 409©.  The bag was then sealed and vigorously shaken to make sure all boot parts were soaked. The boots were soaked in the chemical solution for a full five minutes. Only when thoroughly soaked for at least five minutes did the 50% Formula 409© prove to be effective at killing NZMS. 

A second misunderstanding that many anglers experienced was that the 409 compound used by the researchers was a completely different formulation than that which is sold in spray bottles. Formula 409© is made by Clorox Company and they actually make five or six different chemical combinations that they market as varieties of Formula 409©. The Formula 409© used by the CDFG researchers was a special degreaser formula that is not what is typically available. 

As word spread that Formula 409© was an effective disinfectant the Colorado Division of Wildlife (CDOW) determined that they needed additional information before they could recommend its use. Consequently, they conducted a second series of experiments using Formula 409©. Their research was published in a peer-reviewed article published in North American Journal of Fisheries Management magazine titled Application of Household Disinfectants to Control New Zealand Mudsnails .

The CDOW researchers compared the efficacy of treating with Formula 409© to treatments with the disinfectant Sparquat, a disinfectant not commonly available to the public that is used by some agencies to disinfect their equipment. In the CDOW study the researchers discovered that Formula 409© was only effective in killing mud snails when used at 100% strength in a soak for a minimum of 10 minutes. These researchers questioned the previous claim that a five minute soak in a 50% concentration was adequate to kill the snails as their work showed 100% for 10 minutes was actually required.

Well, it's not just anglers that can get confused about the use of chemicals with invasive species. It turns out that the researchers in Colorado were using the commonly available anti-bacterial formula of Formula 409© which is sold in most stores in spray bottles. They were unaware that the California study had been performed using the degreaser formula. Consequently, we have two different studies of two different compounds with different use recommendations for each. Based on the common availability of the anti-bacterial formula it is likely that the Colorado results are more indicative of what the average angler would experience.

Using Formula 409© to Kill New Zealand Mud Snails
                                                CDFG Study                          CDOW Study
Type of Formula 409©           Degreaser                                Antibacterial
Concentration                         50%                                         100%
Treatment Type                       Full Soak                                 Full Soak
Length of Soak                       5 minutes                                 10 minutes
Both studies note that spraying is not effective

Therefore, using the CDOW information, we can see that it is difficult for the average fisherman to soak his boots and waders in a 100% solution of Formula 409© for a minimum of 10 minutes. While there may be some dedicated anglers who would take the necessary actions, this is not practical for most fishermen.

So, two different studies have shown that two different varieties Formula 409© can kill NZMS if properly used. However, both the California and Colorado studies pointedly noted that their experiments showed that spraying with Formula 409© is ineffective and will not sterilize the gear.  Yet, spraying their boots is what most anglers do.

There is another consideration here which also makes Formula 409© a bad choice as a boot disinfectant. That is the simple fact Formula 409© has only been shown to be lethal for New Zealand mud snails and has not been tested for the myriad of other invasive species that we are seriously concerned about. There is no reason to believe that Formula 409© is an effective disinfectant for mussels, aquatic weeds, whirling disease or any other invader. Despite this, interviews with anglers indicate that most believe Formula 409© is a universal disinfectant that is killing all invasives.

The Formula 409© story illustrates how easy it is for people to misunderstand the information about application of chemicals. Most anglers who believe they are disinfecting their boots by spraying them with Formula 409© also believe that they are fully decontaminating their boots for all species by doing the same. They don’t understand that Formula 409© is a species specific solution. There is no universal chemical disinfectant that will work for controlling aquatic invasive species.

So there you have it, the story of how a misconception got started. I'm sorry to be the one to tell people that spraying their boots with Formula 409© does not make a difference but it’s the truth. We would all love to see a spray that really would disinfect our boots and other gear. However, until it arrives, all we can do is follow the basic premise of inspect clean and dry. 

The political comedian Bill Maher once had a special on HBO titled "Be More Skeptical”, which is sound advice about gear cleaning. If you hear from anyone that there is a recommended procedure for disinfecting your gear check it out before you adopt it as your personal practice. If you ever have any questions, contact the folks at the Center for Aquatic Nuisance Species for information about any aspect of gear cleaning and disinfection. For those of you who are using Formula 409©, it's time to make the kitchen and bathroom sparkle instead of your boots.

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