Archive for the 'Control' Category

The antifeedant and toxic activity of Neudorff’s 3% Iron Phosphate bait on Pomacea maculata


Last November, I was contacted by Lauren Strachan Hall, Research Coordinator for Neudorff North America. Originating in Germany, this company has been a leader in creating natural pesticide products for over 150 years. Ms. Hall coordinates field research for Neudorff, whose guiding principle is to combine a high degree of efficacy with excellent environmental safety.

One of Neudorff’s products, called “Sluggo” (A.I.: 1% iron phosphate), has been effectively used on terrestrial snails in the U.S. and elsewhere, but it is not labeled for aquatic use in the United States. This company has successfully treated invasive, exotic Pomacea canaliculata and P. maculata in Europe and Asia using pelletized iron phosphate baits in water. Ms. Hall expressed an interest in testing a more concentrated product in development (A.I.: 3% iron phosphate), while the company considers E.P.A. registration for its aquatic use in the United States.

Test 2

The protocol called for 8 replicates per treatment with the treatments being 0.5g, 1.0g, 2.0g and 4.0g of NEU1180 HP pellets, plus a “control” of flour-based pellets. The containers were 5.7L plastic containers (30cm X 15cm X10cm). The tops of the containers locked which is important with large Pomacea. Snails were collected from Wellman Pond, east of Tallahassee, Florida. The average weight of the snails was 150g (116g – 178g). Shell height averaged 7.3cm. The protocol called for testing the snails’ appetites at 4DAT, 8DAT, and 12 DAT. Cucumber slices proved to be attractive, long-lasting, and easy to weigh and monitor.


The 3% iron phosphate bait proved to be an attractive to the snails. In fact, the test product appeared more attractive than the flour-based, blank pellets used in the control. The pelletized bait, scattered evenly in the containers, was readily consumed by all snails. The snails were observed daily for “proof-of-life,” e.g. attachment to the side of the container or resistance to a gentle pull on a closed operculum. Deaths were recorded daily. The snails were fed single cucumber slices every 4 days and percent consumption was noted the following day.

In three simple bench tests, Neudorff’s 3% iron phosphate bait appeared to have dose-related, detrimental effects on adult Pomacea maculata in terms of appetite and survival. Supplemental food consumption was reduced by 77% in the 0.5g treatment, 75% in the 1.0g treatment, 100% in the 2.0g treatment, and 100% in the 4.0g treatment. At 12 DAT, survival averaged 92% in the control, 75% in the 0.5g treatment, 50% in the 1.0g treatment, 12.5% in the 2.0g treatment, and 25% in the 4.0g treatment.

Feeding was suppressed at all treatment rates and ceased completely at rates of 2.0g and 4.0g. At those higher rates, 75% of the adult snails were dead by 6DAT. Considering the environmental safety of iron phosphate and the current lack of any safe and effective alternatives, the negative impacts of Neudorff’s 3% iron phosphate bait on food consumption and survival are reasons for optimism for this product’s use to control adult Pomacea maculata. – – Jess Van Dyke


Ebro Delta: The Exotic Apple Snail’s Bridgehead in Europe

The Ebro Delta (350 km2), located in Tarragona at the southern end of Costa Dorada, is the largest wetland in Catalonia and is the second most important natural wetland habitat in Spain. About 8,000 ha of the delta are natural park sites, part of the Natura 2000 network of the European Union. The delta has high biodiversity and productivity, excellent fish and wildlife habitat, and important water purification and storage functions. Plant diversity is extremely rich with 515 species catalogued. Large pools surrounded by giant reed beds occupy the coastal portions. No wonder the Ebro Delta is the second most important bird habitat in Spain. Economic activities include agriculture, fisheries, aquaculture and tourism. Rice cultivation, however, is the dominant use.

On August 1, 2009, the Island Apple Snail (Pomacea insularum) was first documented on the European Continent. Its conspicuous, bright-pink egg clusters were detected on shoreline vegetation along a small irrigation canal, adjacent to a fish farm in the Ebro Delta. The range expansion of the exotic snails was explosive. Within a month, they had colonized half of the interconnected canals in the northern half of the delta (up to 5.1 egg masses m-1) as well as the main river channel (up to 6.2 egg masses m-1). After reviewing the literature, local experts recognized the great potential of widespread economic and  environmental damage.

Government agencies quickly implemented plans to eliminate the pest manually, mechanically and chemically hoping to avoid harmful effects on agriculture and native biodiversity. All emersed vegetation from 16 miles (26 km) of shoreline in the initial area of infestation was harvested and incinerated to no avail. The desiccation of 9,500 hectares of the delta for five months at a cost of 3.5 million € in attempt to eradicate the snails proved fruitless. In spite of these and other extreme measures, “the ability of the Island Apple Snail to thrive and disperse in the Ebro Delta shows that this bridgehead is firmly established,” writes Miguel Angel López of the Catalonian Government Environmental Department.

I have been in communication with a biologist who is currently assisting the frustrating struggle to stem the Island Apple Snail’s invasion of Europe: “The Environmental Department has been hand-collecting adults, putting barrier traps in the irrigation canals, destroying egg clutches, and burning shoreline vegetation in non-sensitive areas to remove egg substrate. They are now using saponins as well. The snail is occupying an area of the delta where there are mostly canals for habitat. The Environmental Department has mapped about 240 km (150 miles) of canals which are infested. We regularly have sustained temperatures of 9 or 10º C during winter here with occasional drops below zero and there has been snow here during two of the last five years, and they seem to be doing just great! Copper is not permitted as there are native bivalve species sharing the irrigation canal habitat. Baits are problematic as the current in the canals rapidly disperses them. Despite the Environmental Department’s efforts with a crew of 30 people, there seems to be no end in sight. The bottom line is more funding is needed to get ahead of this pest. Any suggestions from your experiences would be appreciated.”

O.K., I’ll give it my best shot: Clearly, the situation is dire; the wetlands of an entire continent are at stake. In my opinion, the ultimate solution is biological control via some selective pathogen, though such an organism will not be easy to find (or create). At present, containment is paramount. Accidental transport of the exotic snails to other aquatic sites must be prevented. In my experience, anglers with boats on trailers are most often responsible for the inadvertent dispersal of invasive, aquatic species. In the case of Pomacea, however, aquarium hobbyists have played a major role.

Within the Ebro Delta, I suggest that you focus on Pomacea’s two key vulnerabilities: the conspicuousness of its eggs and its vulnerability to chemical attractants. Continue to collect eggs, as much as manpower will allow, and possibly make some money to subsidize your control efforts. Biotechnology companies in Taiwan are spending huge sums to develop technologies to extract the anti-oxidant Astaxanthin from Pomacea eggs. These companies estimate that the value of the anti-aging, skin care products based on that active ingredient could reach over $400,000,000 annually. Natural Astaxanthin is currently priced at $7000/kg (not a typo). Maybe, a Spanish biotech firm would like to participate and fund the collection of Pomacea eggs in the Ebro Delta!

Regarding baiting, do not underestimate the chemoreception capabilities of the Island Apple Snail. Even with some flow, Pomacea can be drawn to the right attractant. For collection (or poisoning), bait stations make sense. I have shipped Miguel one of our traps with non-toxic bait to test. By doing so, I am not
suggesting that trapping and collecting snails along 240 km of canals is practical. However, with an attractant bait that is also toxic, progress could be made in reducing the population of adult snails. I am in touch with a company that produces an innovative, plant-derived molluscicide, and am eager to incorporate it into the bait we produce for laboratory testing. I will let you know how that goes. Good luck with your battle, Miguel! Posted by Jess Van Dyke

For more information, contact:

Miguel Angel López

Catalonian Government Environmental Department

Trapping Tons of Exotic Snails from Wellman Pond

Newly Planted Wellman Pond (9/2007)

 Officially opened on June 1, 2009, Martha Wellman Park provides a lighted, paved loop around a beautiful pond and a perfect place for us to study the Island Apple Snail (Pomacea insularum). Aside from easy access, the gradual slope of the bathymetry, and relatively firm substrate, the burgeoning exotic snail population made this 15-acre (6.1 ha) pond ideal for our work. We also had a great incentive to learn how to control the exotic snails there. As part of the construction of this stormwater treatment pond, a large number of native, emergent plants were placed along the entire shoreline at a cost of $565,000 – – Soft-stem Rush (142,124), Duck Potato (51,227), Arrowhead (22,673) and Pickerelweed (27,468).  After one growing season, 75% of the emergent plants were gone, including all of the Arrowhead and Pickerelweed.

Dense population of Pomacea insularum (2007)

In the fall of 2007, we began hand-collecting snail eggs and adults in Wellman Pond to save the extensive littoral planting effort funded by the FWCC from the voracious Island Apple Snail. Manually controlling the snails and eggs helped, but clearly something more efficient was needed. In the spring of 2008, we began testing various baiting and trapping methods. We had observed that the exotic snails had excellent chemoreception and could be easily attracted to certain foods. We also noted their proclivity to hide in black plastic (HDPE) flower pots, especially under any broad lip. Finally, we could see that the snail’s mobility was impeded by thin, vertical planes not touching the bottom. Putting this all together, we devised a trapping system that is highly effective on exotic apple snails.

Apple Snail Trap in Wellman Pond 

With funding from Blueprint 2000 and Leon County, we deployed 30 Snail Busters’ Apple Snail Traps (patent pending) in Wellman Pond in 2008 and 2009. As we cleaned and baited the traps, we also collected any eggs and adults we observed.  By the end of 2008, we had removed 4.16 tons of snails and 2,135,200 individual eggs! In 2009, the numbers dropped to 0.89 tons of snails and 1,106,400 individual eggs, in response to a much smaller population. This snail control program has stabilized the aquatic plants and the remaining plants were saved. Since these efforts were instituted there has been no subsequent loss of plants in the pond. The surviving plants are growing and reproducing. We are seeing a lot of new growth in the pond for the first time in the past two years. This is the best barometer of success. Posted by Jess Van Dyke

Wellman Pond (9/2009)

Alabama Fights to Protect the Mobile-Tensaw River Delta

Kill the SnailsI recently spoke with Ben Ricks, District Fisheries Biologist with the Alabama Department of Conservation and Natural Resources (ADCNR), Wildlife and Freshwater Fisheries Division (WFF) about the recent team effort to eradicate exotic apple snails (Pomacea insularum) in Langan Municipal Park Lake and Threemile Creek, Mobile, Alabama (see Recent News). Ben had a positive attitude, “Everything went as well as could be expected given the short period to prepare. We got rid of a bunch of snails!”

While Langan Lake and Threemile Creek are important aquatic assets for Mobile, the urgency of this battle comes from the fact that they are connected to a true ecological gem, the Mobile-Tensaw Delta. Within this National Natural Landmark, more than 300 square miles of marshes, swamps, and bottomlands are now in danger of invasion by the exotic apple snails. This summer, the exotic apple snails were sighted only one mile upstream from one of the most biologically diverse and second largest river deltas in the U.S.

WFF sought assistance and council from a number of experts, volunteer organizations, and public agencies: The City of Mobile, Alabama Department of Environmental Management, Alabama Department of Public Health, Alabama Marine Resources Division, U.S. Fish &Wildlife Service, Environmental Protection Agency, Mobile Baykeeper and the Mobile Bay National Estuary Program. Even Snail Busters contributed to the effort by providing thirty, deeply-discounted apple snail traps.

The control project had a three-pronged approach: trapping adults, scraping the eggs, and treating the adults with copper. Three days before the copper treatments, Snail Busters’ traps were used to assess the initial population. “The traps worked great,” Ben said. “They really did the job!” During the treatment, the minnow traps were used as “sentinel traps” to obtain an estimate of the efficacy of the copper treatment. “Sixty to seventy percent of the snails inside the traps were dead after treatment.”

Two tons of copper sulfate was applied to Langan Pond and Threemile Creek using a blower to achieve the target of 2 ppm copper sulfate (0.5 ppm elemental copper). “Four ppm killed them every time in the lab, but 2 ppm also worked well” Ben said. In deference to preventing non-target mortality, they used the lower concentration. “Not a single fish died,” Ben happily reported. “Some Asiatic Clams (Corbicula fluminea) were killed, but that’s just a bonus, because they are another invasive, exotic species.”

Volunteers, especially hardy souls associated with Mobile Baykeeper, worked diligently to scrape apple snail eggs from the shoreline. “It’s a very time-consuming job,” Ben groaned.  “We’re going to try a pressure washer next year!” He also discussed tentative plans to reduce the dense stands of emersed vegetation that provide excellent reproductive habitat for the exotic snails.

Summing it up, Ben said, “We got a lot of apple snails and made a really good dent in the population, but we going to continue trapping and compare numbers. “So far, pre-treatment rate was 222 snails and post was 32 snails.  A seven-fold decrease isn’t that bad. The bottom line is that we need adequate funding for next year.” Thanks for the update and all the hard work, Ben. The Mobile-Tensaw Delta is certainly worth the fight! Posted by Jess Van Dyke

For additional information, contact WFF Biologist Ben Ricks by phone at (251)-626-5153, or by email,

Video of Lagan Pond from WPMI Ch 15 Mobile:

Image of trap from Press-Register, Bill Starling photographer

Captain Copper

Captain TrialSince 1994, SePRO Corporation has been an innovative leader in aquatic plant management. After turning the tide against highly-invasive hydrilla (Hydrilla verticillata), SePRO’s flagship product, “Sonar” (fluridone), became the world’s leading brand of aquatic herbicides. David Tarver was a big part of that success. For over 30 years, I have known David and found him to be an excellent source of information on aquatic resource management. That is why, when he asked me to test four of SePRO’s chelated copper products (“K-Tea,” “Nautique,” “Komeen,” and “Captain”) on Pomacea insularum, I was flattered and excited. I promised speedy, conclusive results. How hard could it be? And so, the adventure began.

Bench tests are inexpensive, repeatable, and fairly reliable, though efficacy is always better in a container than in the environment. One simply places the test organisms in identical containers with identical volumes of water, varies the rate of the test chemical, waits 48 or 96 hours, and determines mortality. If, say, a fish rolls over, flairs its opercula, and no longer moves with eyes bulging, it is safe to say that the concentration of test chemical is lethal. Simultaneously, if fish are thriving in the “control” container with no test chemical added and in containers with lower concentrations, the lethal rate can be determined. No problem. Bring on the snails!

Of course, life is full of surprises. Unlike fish and other aquatic organisms, apple snails can present a number of unique challenges to the researcher. First, like fish, Pomacea also have an operculum, but it is not a bony flap protecting the gills; it is a well-sealed “trap door” that chemicals cannot penetrate. Secondly, Pomacea are amphibious, not aquatic. If an apple snail detects a toxic chemical, it can simply crawl out of the test solution. Thirdly, Pomacea are strong enough to push the tops off of containers and crawl away. Finally, a dead apple snail with its operculum closed looks exactly like a live one for many days. As I told David, those are the reasons (excuses?) a simple experiment took me 9 months and 14 trials!

From the first four trials in the fall, it became clear that “Captain” had an edge on the other products that couldn’t be explained by the concentrations of the active ingredient, as metallic copper: Captain (9.1%), Nautique (9.1%), Komeen (8.0%), and K-Tea (8.0%). So, as winter approached, all I had to do was focus on one product, determine the lethal rate, repeat the trial a few times, and report the results. It seemed simple, until I realized that water temperature played a key role in efficacy. At 20o C, all test animals survived, but all died (except control animals) when an identical test was repeated at 28o C. Obviously, the lethal effects of copper to Pomacea are directly related to metabolic rate, but in a greenhouse with only partial control of temperature, precisely repeating bench tests proved impossible.

I did come away with some tentative, experimental results that are worth reporting, however. First, as mentioned above, I suggest using “Captain” to control exotic apple snails. Perhaps, it is the “double chelation” that makes it more lethal by keeping it in solution longer, but it stands above the rest. Secondly, treat when water temperatures are warm (>270 C or 800 F). Of course, that will require more caution regarding non-target damage, i.e. “fish kills.” Third, because Pomacea can completely “clam up” for at least 24 hours, split treatments make sense. Fourth, coordinate physical removal with treatments, if practical. The snails should become vulnerable to hand-picking, as they move to areas shallow enough to extend their snorkels or to even leave the water.

What about the rate? The maximum label for “Captain” is 1.0 ppm (A.I.) or 3 gallons/ac-ft. (see below), but Pomacea insularum were vulnerable at much lower rates. In fact, higher rates may be counter-productive in that snails tended to close their opercula. At 230 C, the snails produced mucus at 0.2 ppm and, at 0.4 ppm, they lay on the sides with opercula open. After 96 hours, 0.4 ppm was lethal at that cooler temperature. At 270 C, 0.2 ppm was lethal after 48 hours. As mentioned earlier, bench test tend to over-estimate toxicity compared to the natural environment. Therefore, if you want to play hard-ball with exotic apple snails, treat with “Captain” at 0.3 to 0.5 ppm A.I. twice, 24 to 48 hours apart.

I am concerned about presenting these tentative results. Someone needs to fund Dr. Linda Nelson at USACOE/WES to conduct more detailed and controlled time/concentration research on chelated copper and exotic apple snails (Hint: SePRO). In any case, “Captain” appears to be your best bet, but carefully read the label. I hope to be able to try this product in the field soon and will report back on the results. My last suggestion is to read my earlier post about copper, entitled “The Copper Question.” It is dangerous to fish, if not used carefully, and is rather non-selective in terms of invertebrates. The environmentally sound way to use copper is seldom. Posted by Jess Van Dyke 

P.S. I have no relationship with SePRO, financial or otherwise. My thoughts are my own. You are responsible for the careful use of any pesticide.

Label for “Captain”:

SePRO Corporation:

Aloha, Poi?

TaroWhen the first Polynesian settlers arrived in the Hawaiian Islands some 1500 years ago, they were smart enough to carry with them viable corms of their food staple, Taro (Colocasia esculenta) or “kalo” in Hawaiian.  Even today, every part of this plant is eaten with gusto in Hawaii. Rich in vitamins and minerals, the leaves are used to wrap meats and steamed to make “laulua.” More importantly, the corms are baked or steamed and mashed with water to produce dough-like “poi.” This sweet, starchy pudding is low in fat, high in Vitamin A and complex carbohydrates, and very easy on the stomach. In fact, “poi” is so gentle and nutritious that it is used as a milk substitute for babies with allergy problems.  Taro is more than just an excellent food source, however. According to the Hawaiian creation chant, “kalo” is the elder brother of the first Hawaiian, and thus, of the entire Hawaiian race. In Hawaii, the taro plant is a sacred, cultural icon and an important link to past traditions.

In spite of a growing demand for taro products, yields have declined in Hawaii over the past 50 years, with the lowest production (4M lbs) recorded in 2007. Urbanization took an early toll, but diseases and pests have had a major, negative influence on taro production in recent years.  Most notably, the invasive, exotic, Channeled Apple Snail (Pomacea canaliculata) has become a severe agricultural pest in the taro pondfields, called “lo’i”.  First introduced in Maui in 1983-84 for the aquarium trade and an alternative food source, P. canaliculata is now found on every major Hawaiian island, save one. The three most important taro growing communities are all heavily infested, along with the lower reaches of most streams, numerous wetlands and estuary sites (Lach and Cowie, 1998; Cowie, Hayes and Levin, 2004).

Though generating $2.7M in 2008, 105 taro farms survive tenuously in Hawaii today because of taro imports, land, water, and labor shortages, plus an array of new diseases and pests. The Channeled Apple Snail, however, may be the one pest that pushes taro farmers over the edge. Snail control methods in Hawaii include water level management, hand picking of eggs, herding ducks, employing screening on pipes and in canals, and carefully inspecting introduced plants. Nevertheless, the snails continue to take a heavy toll while adding considerable labor costs. Typical losses due to snails are 20% of the crop, but heavily infested fields can be completely wiped out, destroying 10-12 months of time and effort.

I’d like to send some of our Apple Snail Traps to Hawaii to see if they can help these determined farmers, but I lack the right contacts. All I can say is these traps are working well here in Florida. I have had the privilege of visiting Hawaii in the past, and the view of the taro fields near Hanalei was the most beautiful agricultural setting I have ever seen. One day, I hope to see those emerald fields again. “Aloha” is a word used in Hawaii to say either “hello” or “goodbye.” So, I say longingly, “Aloha, Poi” hoping that it doesn’t mean “goodbye” to such a sacred and nutritious Hawaiian food and a wonderful, traditional way of life. Posted by Jess Van Dyke

Statewide Strategic Control Plan for Apple Snails in Hawaii (9/30/2006):

Rematch: Pomacea versus the Red Fire Ant


While collecting thousands of Island Apple Snail (Pomacea insularum) egg clusters from Wellman Pond, we often speculated on what ferocious predator could have elicited such high reproductive capacity in this South American snail through evolutionary time. Initially, we fantasized about some large reptile, maybe a 20’ Snail Anaconda (Eunectes pomaceoraptor?), feeding so effectively on apple snails in the Argentine rivers and marshes that the remaining few adults had better reproduce prolifically for the species to merely survive. Then, as we began to notice the numerous ant bites received while wading through the shoreline plants, it came to us. Maybe, the ferocious predator wasn’t all that large. This notion was solidified when our 4-ton pile of disposed snails became one giant Fire Ant bed!

The Red Imported Fire Ant (Solenopsis invicta) and the exotic Apple Snails (Pomacea canaliculata & P. insularum) have two common traits: They are both highly invasive in the southern U.S. and their native ranges in South America generously overlap. Surely, they co-evolved in a predator-prey relationship with hydrology as a key component. Fire Ants are, indeed, ferocious predators of snails, having caused the extinction of a native tree snail in the Florida Keys (Forys et al, 2001). Stevens et al (1999) documented that Fire Ants attacked native apple snails (P. paludosa) in Florida that became “exposed during dry down conditions.” Yusa (2001) observed that “when egg masses [of P. canaliculata] were experimentallyplaced on levees [infested with Fire Ants], on average 50% of the eggs were lost within two days in March and 38% were lost within threedays in August.No eggs were lost when ants weresuccessfully excluded by water.” Way et al (2009)noted that “periodic drainage . . . enables [the tropical fire ant] to join the predator complex . . . valuable for ant-based control of pests such as snails” in rice paddies.

The current range of the exotic Red Fire Ant in the U.S. encompasses the projected range of the invasive South American Apple Snails. Certainly, predation by the Fire Ant will provide some friction to the rate of expansion of the exotic apple snails in the U.S., especially in areas with fluctuating water levels. Can we take further advantage of this ancient predator-prey relationship? Based on Yusa (2001), Way (2009), and personal observations, it appears a short period of water level manipulation in the presence of red fire ants can have a deleterious effect on apple snail reproduction. When the bases of shoreline plants are exposed in Wellman Pond, for example, numerous Red Fire Ants begin eagerly scouting for egg clusters. I am inclined to ask the Parks personnel not to treat the fire ant mounds there. Periodic, partial “drawdowns” also seem warranted. Let the rematch of invasive Pomacea and the Red Fire Ant continue! Posted by Jess Van Dyke

UF’s Excellent site on Red Fire Ants:

National Geographic video on Fire Ants:

About Snail Busters

The Snail Busters Blog was created to facilitate communication between aquatic resource managers who are fighting the spread of invasive, South American apple snails, specifically Pomacea maculata (formerly P. insularum) and P. canaliculata, in the U.S.

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