








































Abstract:  Zebra mussels are an invasive species that are very harmful to the environ-
ment and therefore cost society a considerable amount of money. Most of the previous 
attempts to eliminate zebra mussels were either ineffective or caused damage to other 
organisms. Zequanox is a biopesticide made by Marrone Bio Innovations, and its ultimate 
purpose is to eliminate zebra mussels. However, Zequanox can change the water qual-
ity for very short periods of time and can harm other aquatic organisms in large doses. 
After extensive research on this controversial subject, Zequanox has been found to be a 
viable option if used in regulated doses.

Aisthesis      Volume 7,  201629

Zequanox: A Potential Solution to Zebra Mussels
by Bailey Murawski

Introduction
 Zebra mussels (Dreissena polymorpha) are an 
infamous invasive species in the United States. 
Originating from the Caspian Sea in Europe and 
arriving in the United States by ballast in ships in 
1988, zebra mussels spread throughout the Great 
Lakes and the Mississippi River. They have rapidly 
spread to over 20 states in the United States, readily 
attaching themselves to hard surfaces like boats and 
motors and then releasing in other lakes (National 
Park). Issues associated with zebra mussels, such as 
clogged pipes and polluted drinking water, will not 
be resolved without active means of prevention. 
Zequanox, a biopesticide that comes “from a strain 
of the naturally occurring bacteria Pseudomonas 
fluorescens” (P. fluorescens strain CL145), has been 
found to be a productive and efficient way to kill 
zebra mussels (Whitledge et al., 2014). Zequanox is 
unique in the fact that it is not made from synthetic 
chemicals and solutions, yet it is still an effective 
pesticide for zebra mussels. 
 The concern is that Zequanox could not only kill 
off the harmful invasive mussels, but also affect the 
water quality, harm native aquatic life, and change 
the ecosystem. This article will weigh the effects 
of zebra mussels and Zequanox while considering 
an important question: Is there too much risk 
in using Zequanox so that we must find another 
solution, or even simply live with the infestation of 

zebra mussels? I will conclude that the answer to 
the question is this: Zequanox is a viable solution 
to eliminate zebra mussels because it does little or 
no damage in multiple areas. The problem of zebra 
mussels in the United States is more harmful than 
the potential side-effects of Zequanox.

Zebra Mussels
 Zebra mussels are damaging in multiple 
dimensions. Because of their ability to reproduce so 
rapidly, they are almost impossible to control. The 
Virginia Department of Game and Inland Fisheries 
(2016) declared that an adult female zebra mussel 
can produce up to a million eggs each year, and it is 
very likely to find a square meter area with 100,000 to 
1,000,000 zebra mussels. The National Oceanic and 
Atmospheric Administration (n.d.) agrees that up 
to 700,000 have been found per square yard area on 
boats, pilings, and pipes. This rate of reproduction is 
extremely hard to control.
 One very important risk that follows the takeover 
of zebra mussels is the quality of drinking water. 
Okanagan WaterWise warns that “these invasive 
mussels promote toxic algae which would pollute 
our drinking water and also clog drinking water 
intake and distribution systems” (2012). Additionally, 
Okanagan Waterwise warns that addressing these 
drinking water problems could cost millions of tax 
dollars to fix. Therefore, without prevention, zebra 



Zequanox: A Potential Solution to Zebra Mussels 

Aisthesis      Volume 7,  201630

mussels will continue to multiply, causing more and 
more drinking water intakes to be clogged. 
 Zebra mussels also pose a threat to fish and 
other aquatic organisms. Because they filter out 
many microscopic organisms, they are also taking 
away a major food source from fish (Virginia, 2016). 
In fact, the National Oceanic and Atmospheric 
Administration declares that “fish stocks and 
conditions have declined in many of the Great 
Lakes.” When the fish decide to eat the zebra mussels, 
fish waste energy crushing their shell for a result 
lacking in nutritional value (National Oceanic, n.d.).  
Along with that, “Zebra mussels attach themselves to 
native mussels so the natives can’t eat, breathe, or 
reproduce” (National Park, n.d.). The Government 
Accountability Office estimates that zebra mussels 
will cause native mussel species to decline to as 
much as 50 percent in the next 10 years, with up to 
140 extinct species (Western, 2010). Because zebra 
mussels will be killing off many different bottom-
dwelling species by taking their food, the mussels 
will also be killing many other animals that eat those 
bottom-dwelling species, having a significantly 
negative impact on the food chain. 
 Zebra mussels will be, and are, an enormous 
financial cost to the United States. For example, the 
United States will lose close to $3.7 million from 
lost boat sales and required maintenance on 
docks and marinas, and a boat owner will have 
to pay between $1,000 and $2,500 a year for 
maintenance (Okanagan, 2012). These values are 
minor compared to some that have been recently 
recorded. “U.S. Congressional researchers have 
estimated that Dreissenid mussel infestations in 
the Great Lakes area has cost the power industry 
$3.1 billion between 1993-1999, with an economic 
impact to industries, businesses and communities 
of more than $5 billion,” and “[a]verage costs from 
1989-1994 for facilities with a Great Lakes basin 
water intake were over $4 million per respondent for 
zebra mussels” (Western).  If their spread continues, 
these costs will continue to occur because of the 
continuous maintenance. The Missouri Department 
of Conservation expects damage costs due to zebra 
mussels in North America to be in the billions in 
the next decade (2010).

Zequanox
 Zebra mussels undoubtedly cause many pro-
blems, without giving any benefit, which is why 
Zequanox is being considered to fix the problem. 
Zequanox is a naturally made pesticide by Marrone 
Bio Innovations and targets zebra and quagga 
mussels (Whitledge et al., 2014). It is made from 
a natural bacteria strain called Pseudomonas 
fluorescens CL145A which is commonly found in soil 
and water, and it protects plants from disease while 
helping them grow (Ganeshan and Kuman, 2005). 
Zequanox is used in the form of a dried powder and 
is administered directly into the infested body of 
water (Meehan, 2014).
 Zequanox seems to be good substitute compared 
to other products that have been tested to kill zebra 
mussels. Unlike other chemicals, zebra mussels do 
not see Zequanox as a danger and will readily ingest 
it. Once this happens, the Zequanox will deteriorate 
the lining of the zebra mussels’ stomachs, ruin their 
digestive system, and cause death (Marrone, n.d.). 
Zequanox also kills zebra mussels more quickly than 
do other products. 

Meehan’s Study 
 There are many known benefits to using 
Zequanox; however, this article examines whether 
the benefits outweigh the costs of this pesticide. Sara 
Meehan conducted a study to research some of the 
areas of concern, such as water quality and the health 
of other aquatic organisms being introduced to 
Zequanox. Meehan divided the study area into two 
treatment groups and a control group each containing 
naturally settled and seeded mussels. Treatments 1 
and 2 were treated with Zequanox, while the control 
was not. Aeration devices were used to administer 
oxygen into the water, keeping the levels of dissolved 
oxygen (DO) in the water fairly constant in Treatment 
1. Because Meehan knew that Zequanox can alter the 
levels of DO in water, she wanted to see if the results 
of use of aeration devices in Treatment 1 would give 
differ from results in Treatment 2, which wouldn’t 
have aeration devices. If DO levels become too low, 
aquatic animals may not have enough oxygen to go 
through the process of respiration, resulting in their 
mortality (Murphy, 2007). Meehan also observed 
different parameters of water quality like turbidity 
and total organic carbon (TOC) during her study. 



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Aisthesis      Volume 7,  201631

Turbidity is a measure of haziness in the water, while 
TOC is the amount of organic matter in the water; 
both of which can affect the carbon cycle (Murphy, 
2007) and aquatic organisms that rely on the quality 
of the water to survive. 
 The mortality rate of seeded mussels in Treat-
ment 1 was 75% and only 56% in Treatment 2. The 
difference in mortality between the two could have 
resulted from the decrease of DO in Treatment 2, 
causing the mussels to avoid ingesting the Zequanox. 
Additionally, naturally settled mussels had a mortality 
rate of 46% in Treatment 1 and 65% in Treatment 
2. The aeration devices being placed so close to the 
naturally settled mussels could have disturbed them 
enough to avoid ingesting the Zequanox, causing a 
lower mortality rate in Treatment 1. Temperature 
and pH levels in the treatment groups did not 
differ considerably from those in the control group. 
Furthermore, there was an increase in turbidity in 
both treated areas, an increase in TOC in both treated 
areas, and a decrease in DO levels in Treatment 1. 
However, turbidity, TOC, and DO levels all returned 
to normal within 24 hours. 
 Meehan also studied different species and fam-
ilies of aquatic organisms following Zequanox 
exposure. She placed many organisms such as 
nonbiting small flies (Chironomus), aquatic sowbugs 
(Asellus aquaticus), mayflies (Ephemerella ignita), 
blue mussels (Mytilus edulis), freshwater mussels 
(Anodonta), water fleas (Daphnia pulex), European 
freshwater crayfish (Austropotamobius pallipes), and 
freshwater snails (Lymnaea peregra), and brown 
trout (Salmo trutta) in different concentrations of 
Zequanox and monitored them. The results showed 
that all the organisms tested except Salmo trutta 
had little to no mortality at a concentration of 100-
200mg/L being administered every 12-24 hours for 
72 hours. However, even lower concentrations of 
Zequanox lead to a high mortality rate for Salmo 
trutta. 

Whitledge et al. Study
 To further investigate whether Zequanox is 
a viable solution to the zebra mussel problem, 
this paper will analyze another study: Gregory E. 
Whitledge et al. explain and interpret their research 
on the effects of Zequanox in two different sets of 
controlled environments. In the 2012 trial, Whitledge 

et al. studied three pairs of control groups and 
experimental groups of equal area. The experimental 
group was treated with Zequanox, and the control 
group was not. To determine whether the surface 
the zebra mussels are attached to will affect their 
mortality rate while being treated with Zequanox, 
zebra mussels were tested from a log that was 
submerged into the treated area (wood substrate), 
the bottom of the lake (benthic substrate), and rigid 
mesh chambers placed in the treated areas. 
 Zebra mussels attached to the benthic substrate 
had a mean mortality rate in the treatment plots of 
42.6% one day after treatment, and 91.7% one week 
after treatment. Additionally, the control plots had 
a mortality rate of 0.41% one day after treatment, 
and 4.5% one week after treatment. Similarly, zebra 
mussels attached to wood substrate had a mean 
mortality rate in the treatment groups of 37.9%, and 
1.7% in control groups one day after treatment. Two 
weeks after treatment, zebra mussels placed in the 
mesh chambers had a mean mortality rate of 97.1% 
in treatment groups, and 11.1% in control groups. 
With these results, Whitledge et al. conclude that the 
type of substrate does not influence the mortality 
rate; therefore, Zequanox is effective in killing zebra 
mussels attached to all the common types of surfaces 
they are typically found.

 In the 2012 trial, Zequanox concentration did not 
exceed 124 mg/L. Figure 1 shows how turbidity 
changed from the addition of Zequanox.

 Twenty-four hours post-treatment, the average 
turbidity reading for the treatment groups was 9 
NTU compared to 1.2 NTU in controls groups.  DO 
levels decreased 24 hours after initial treatment, but 
the DO levels were insignificant on the overall water 



Zequanox: A Potential Solution to Zebra Mussels

Aisthesis      Volume 7,  201632

quality observations because they quickly returned 
to normal levels once the barriers were removed. 
Levels of pH in the experimental groups were also 
fairly constant with the control groups. Additionally, 
water samples from the treatment groups and the 
control groups were tested for BOD, Chlorophyll a, 
Phosphorus, Nitrogen, and Ammonia, and all were 
either undetectable or the same as in the control 
groups. 
 In the 2013 trial, Whitledge et al. wanted to 
investigate how effective Zequanox would be if it 
were to be injected approximately 0.3 meters above 
the bottom of the lake. These results elude to how 
quickly and efficiently Zequanox spreads while also 
killing zebra mussels around the area that it was 
administered. Whitledge et al. comment on the 
results of this trial:

At 1-d post-treatment, settled mussel mortality 
averaged 0.8% in control samples, 82.9% at 
locations < 5 m from Zequanox SDP application 
points, 11.1% at locations > 5 m from application 
points, and 73.6% at locations shallower than 
application points . . . ; mortality was significantly 
higher at locations < 5 m from application points 
and in shallow areas within the area enclosed by 
the barrier compared to control sites. 

 With that information, Whitledge et al. conclude 
that Zequanox is most effective in killing zebra 
mussels up to 5 meters from where it is injected. This 
means that Zequanox only needs to be administered 
close to the bottom of the treated area, and it will still 
be just as effective as if it were administered at many 
different depths. 
 The average turbidity reading for the treatment area 
at the substrate was 177.7 NTU, and 26.5 NTU at the 
surface. The reading in both areas combined decreased 
to 46.6 NTU 17.5 hours following treatment.  A decrease 
in DO levels was observed as it was in the 2012 trial, 
with 7.2 mg/L inside the barrier, and 8.5 mg/L outside of 
the barrier. However, unlike in the 2012 trial, DO levels 
returned to normal within 2 hours of barrier removal. 

Discussion
 Zequanox has been shown to be extremely 
effective in killing zebra mussels. Results show 
that mean mortality rates in treatment groups are 

significantly higher than in controls group. This gives 
one reason to investigate the other effects Zequanox 
may have. 
 These studies were done under extreme con-
ditions, as the researchers did tests with large 
concentrations of Zequanox, concentrations that 
would not be permitted in open water. Zequanox 
use in open water cannot exceed a concentration of 
200mg/L and will usually be used at a concentration 
of 150 mg/L (Meehan, 2014). The required smaller 
amounts of Zequanox indicate that in reality 
Zequanox might not be as harmful as the tests lead 
on, because it will be so diluted. 
 With that said, Zequanox will be harmless to 
most fish if regulations are followed. Mortality rates 
in fish occur in concentrations above 200 mg/L, 
meaning that fish would only experience death in 
hypothetical situations. Fish are not affected by the 
Zequanox; they are affected by the changes in water 
quality like levels of dissolved oxygen, again showing 
that following regulation will resolve this problem. 
Salmo trutta mortality is definitely a factor in this 
argument, as it occurs even in low concentrations. 
When deciding where and how to use Zequanox, 
Salmo trutta will have to be taken into consideration. 
Additionally, strategies could be developed to detour 
the Salmo trutta away from treated areas. 
 Even though turbidity, TOC levels, and DO 
levels changed with the use of Zequanox, they all 
returned to normal levels within 24 hours of being 
administered. This indicates that Zequanox does 
not permanently change water quality. This change 
was observed in high concentrations whereas 
lower concentrations had less of a change. Thus, if 
regulations are followed, these small changes will be 
even smaller. 
 One of the reasons that Zequanox is being used 
to kill zebra mussels in the first place is because zebra 
mussels are financially detrimental. It is rational to 
ask whether it is cost efficient to be using Zequanox, 
or if it causes more debt than it is worth. With this 
said, a booklet addressed to the Douglas County 
Commissioners asserts that “Steve Hirsh, DNR, 
estimated in an email to John Reynolds on March 
25th that anticipated Zequanox treatment costs are 
currently $10,000 per acre” (Lindquist et al., 2011). 
With this information, it can be determined that 
a product like this does not come without a cost. 



Zequanox: A Potential Solution to Zebra Mussels

Aisthesis      Volume 7,  201633

Although it is very expensive, it is very effective 
and could alter the negative effects caused by zebra 
mussels in many lakes around the United States. 
In theory, if the Zequanox works well enough to 
eliminate zebra mussels and they do not spread 
further, they should no longer be costing the United 
States any money. Although this scenario isn’t totally 
realistic, it demonstrates that Zequanox is going 
to significantly decrease the financial burden even 
without a 100% mortality rate. 

Conclusions
 In conclusion, Zequanox should be used to kill 
zebra mussels. From the studies that confirm the 
harmless effects to water quality and other native 
aquatic organisms, it is clear that Zequanox has 
less harmful effects than do zebra mussels. It has 
also been predicted that Zequanox use will cost 
the United States a lot less financially compared to 
zebra mussels, making it the best option monetarily. 
Zequanox is a superior solution to this destructive 
problem. 

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Pseudomonas fluorescens, a potential bacterial 
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Lindquist, Lois Sinn; Huettl, Bonnie; Towley, Carl 
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2015.

Marrone Bio Innovations (n.d.) Zequanox for Open 
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polymorpha) Control in Irish Waters. Submitted 
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