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Thomas Schmit 

Manager of Regulatory Affairs Tel: (414) 410-7230, Fax: (414) 247-8172 

E-mail schmitt@liphatech.com

3600 W. Elm Street 

Milwaukee, WI 53209

Public Information and Records Integrity Branch (PIRIB) 

EPA Office of Pesticide Programs (7502C) 

1200 Pennsylvania Ave. NW 

Washington, DC 20460-0001 

Submitted through regulations.gov to 

Docket ID Number EPA-HQ-OPP-2009-0684 December 2, 2009 

To the Docket: 

Liphatech, Inc., is the registrant of Rozol Prairie Dog Bait, and we submit this public comment to 

the electronic docket in support of our product. Liphatech is committed to good stewardship of our 

products, and has dedicated a large amount of time, effort and money to develop product labeling, 

cautions and use directions that are protective of nontarget wildlife. We will be submitting several 

comments to this docket, in order to clearly address the specific topics of concern to this docket. 

In this particular comment, we submit responses to the EPA’s “Question to the public for 

consideration” as posted to the docket under ID EPA-HQ-OPP-2009-0684-0018. Many of the 

questions posed ask commenters to compare Rozol (containing chlorophacinone active ingredient) 

to zinc phosphide baits used to control black-tailed praire dogs. We do not know why this 

comparison is requested, as there is no mention of zinc phosphide in the petition, nor other 

discussion of why such a comparison is informative on the matter at hand, nor any information 

about how such a comparison would be used. 

In addition, many of the questions have already been thoroughly addressed, and are not the 

subject of disagreement or controversy. Nevertheless, we will reply to each question with the 

information we have available. EPA’s questions are re-printed here in bold: 

I. Black–Tailed Prairie Dog Mortality

1. Time to mortality for animals consuming Rozol bait, in comparison to zinc phosphide

Zinc phosphide baits cause mortality within several minutes to several hours following ingestion, 

depending on the amount of bait consumed, the size of the animal, and other factors. 

With Rozol chlorophacinone baits, death occurs beginning 4 to 5 days after bait consumption, and 

may be for several weeks, depending on the amount and frequency of bait consumption, the size 

of the animal, and other factors. In the large-scale efficacy study sponsored by Liphatech, 

carcasses were discovered between days 10 and 25 following application of the bait. 

(Information from the Zinc Phosphide RED, published July 1998 by EPA, “Potential Risks of Nine 

Rodenticides to Birds and Nontarget Mammals: a Comparative Approach,” published in July 2004 

by EPA, the Rodenticide Cluster RED, published July 1998 by EPA, Liphatech’s efficacy study 

MRID 47333602, and personal experience of Liphatech researchers) 

2. Susceptibility of prairie dogs to predation after consuming chlorophacinone, in 

comparison to zinc phosphide.

Liphatech researchers (and others) have reported observing “intoxicated” prairie dogs on the 

ground surface following application. These animals appear to have slowed reactions and do not 

flee from encroaching humans in the same manner that is typical of non-poisoned animals. This 

would appear to make them more susceptible to predation than non-poisoned prairie dogs. The 

Liphatech field efficacy study reports that five such “intoxicated” prairie dogs were observed on 2 of 
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the six study sites, and all were observed at least 10 days following bait application. We have no 

data concerning the length of time this occurs. This type of information will be gathered in 

additional studies that we intend to conduct before the end of the current use season in the spring 

of 2010, if possible. 

Prairie dogs that have ingested a relatively large dose of zinc phosphide bait can begin convulsing 

and dying within several minutes following the ingestion. Liphatech researchers have observed 

convulsing prairie dogs on the ground surface following zinc phosphide bait application, but we 

have collected no specific data on the prevalence of this occurrence. (Information from Liphatech’s 

efficacy study MRID 47333602, and personal experience of Liphatech researchers.) 

3. The extent to which prairie dogs die above or below ground after consuming 

chlorophacinone, in comparison to zinc phosphide.

The Liphatech field efficacy study involved placing bait in more than 11,400 prairie dog burrows 

covering approximately 144 acres. Nine (9) prairie dog carcasses were discovered on the ground 

surface on and around the treated plots. 

We have no equivalent quantitative information concerning sites where zinc phosphide baits were 

applied. 

4. Other observations regarding prairie dog deaths after consuming chlorophacinone, in 

comparison to zinc phosphide.

We have no additional information to submit. 

II. Secondary Exposure to Non-Target Organisms 

5. Identity of predators and scavengers of Black-tailed Prairie Dogs, and other exposed 

animals.

The Liphatech field efficacy study did not attempt to identify predators or scavengers that 

actually consumed or removed carcasses from the study plots. The study report shows the 

following wildlife was observed on and near the study plots, which were located in Kansas 

and Nebraska: burrowing owl, meadow lark, horned lark, killdeer, eastern cottontail rabbit, 

mourning dove, red-tailed hawk, great blue heron, northern harrier, pigeon, rough-legged 

hawk, coyote. 

6. Observations of chlorophacinone poisoning incidents among such animals, including 

chlorophacinone concentrations found in non-target carcasses.

A single rabbit carcass was recovered from the treated area in the Liphatech field efficacy 

study, but this is not a predator or scavenger. 

A badger carcass was discovered near an area treated with Rozol bait in Kansas. The 

discovery was reported to Liphatech, and subsequently reported by us to EPA. The carcass 

was submitted to the US FWS for analysis, and the analysis of this carcass is reported in the 

comment submitted to this docket by the National Fish & Wildlife Forensics Lab (document 

ID EPA-HQ-OPP-2009-0684-0039) 

We have no other firsthand knowledge of nontarget mortalities associated with the use of 

Rozol Prairie Dog Bait, and no other incidents have been reported to us. The EPA’s risk 

assessment document (document ID EPA-HQ-OPP-2009-0684-0003) alleges small number 

of additional incidents, of which we have no firsthand knowledge and no information 

information reported to us by another party. 

7. Toxicity of chlorophacinone to avian and mammalian predators and scavengers that feed 

on Black-tailed Prairie Dogs.

We have no additional information to submit. 

8. The speed and frequency at which prairie dogs are expected to be scavenged.

We have no additional information to submit. 
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9. Information regarding chlorophacinone exposure pathways to the American burying 

beetle and any other relevant information.

We have no additional information to submit. Stakeholders should be aware that Liphatech 

sponsored and submitted to EPA a study to look for possible effects from chlorophacinoneon these 

endangered beetles. This study, conducted by recognized experts at Ohio State University, looked 

for reproductive effects on beetles feeding on carcasses contaminated with chlorophacinone 

residue, and for possible effects on the beetles after multiple generations feeding on 

chlorophacinone-contaminated carcasses. No adverse effects were seen. (From MRID 47383001) 

10. Other relevant data pertinent to the effects of chlorophacinone on nontarget organisms.

We have no additional information to submit. 

III. Exposure to Listed Species

11. Expected co-occurrence of listed species and chlorophacinone use.

We have no additional information to submit. 

IV. Carcasses – Monitoring and Removing

12. The percentage of the overall number of target animals killed from an application of bait 

that is likely to be found during carcass searches.

The Liphatech field efficacy study involved placing bait in more than 11,400 prairie dog burrows 

covering approximately 144 acres. Nine (9) prairie dog carcasses were discovered on the ground 

surface on and around the treated plots. It is impossible to accurate quantify the number of prairie 

dogs actually killed during a baiting operation, so it is not possible to express the percentage as 

specified in this question. 

13. The practicality of possible regimens for monitoring and removing target species 

carcasses, including a daily search regimen.

The question of “practicality” is highly subjective; a procedure that may be considered 

practical by one applicator may be considered highly impractical by another. 

We have no additional information to submit. 

V. Chlorophacinone vs. Zinc Phosphide

14. Relative advantages of chlorophacinone over zinc phosphide (e.g., cost; efficacy; and 

labor requirements for pre-baiting, application, and post-application carcass removal).

The first FIFRA Section 24(c) SLN registration of Rozol Prairie Dog Bait was requested by the 

Kansas Department of Agriculture and the ranching community in that state. In the letters they 

wrote supporting the SLN regisration of Rozol, the user community expressed dissatisfaction with 

the other control options that were available to them at that time. Various letters that we received 

and forwarded to the Kansas Dept. of Agriculture included claims that zinc phosphide baits are 

labor intensive, sensitive to weather and don’t always give adequate control. 

We have no additional information to submit. 

15. Evidence of bait-shyness/bait-avoidance reducing the efficacy of zinc phosphide.

The labels for the zinc phosphide baits used to control prairie dogs require that the user “prebait” 

the treatment area with untreated grain. The product labels do not specifically state the reason for 

this prebaiting requirement. It is Liphatech’s understanding that the purpose of this requirement is 

to “condition” the animals to taking this type of bait. 

We have no additional information to submit. 

16. Situations, such as particular rangeland conditions, where chlorophacinone may be 

used but zinc phosphide cannot.

The zinc phosphide active ingredient in baits is rapidly degraded by moisture from rain, snow or 

heavy dew. 
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17. Number of acres treated with chlorophacinone and with zinc phosphide, at the state, 

county or other level.

We have no additional information to submit. 

18. Effect of chlorophacinone product registrations on overall acreage treated for prairie 

dogs (whether with zinc phosphide or chlorophacinone).

We have no additional information to submit. 

VI. Alternative Management Strategies 

19. Alternative prairie dog management strategies (non-pesticidal control techniques), such 

as managing the height of prairie grass (e.g., feasibility, effectiveness, examples, 

advantages and disadvantages of such alternative strategies).

We have attached the following documents: 

Efficacy of Visual Barriers in Reducing Black-Tailed Prairie Dog Colony Expansion, by Joel 

W. Merriman; Phillip J. Zwank; Clint W. Boal; Terry L. Bashore, Wildlife Society Bulletin, Vol. 

32, No. 4. (Winter, 2004), pp. 1316-1320 (we believe that this is copyrighted material). 

Use of Natural Vegetative Barriers to Limit Black-tailed Prairie Dog Town Expansion in 

Western South Dakota, David F. Terrall Master of Science thesis, South Dakota State 

University 2006 (we believe that this is copyrighted material). 

Ranching and Prairie Dogs (invited paper), by Dustin Long and Joe Truett, 

USDA Forest Service Proceedings RMRS-P-40. 2006 (we believe this to be a public 

document from a US government agency). 

VII. Economic Impact of Prairie Dogs

20. Quantitative studies of damage to rangeland from uncontrolled prairie dogs.

We have no additional information to submit. 

21. Evidence of improvements in forage or livestock production resulting from use of prairie 

dog bait (e.g., increased weight gain by individual animals, ability to increase stocking rates, and/or 

decreased requirements for supplemental feed). 

We have attached the following document: 

Are livestock weight gains affected by black-tailed prairie dogs? byJustin D. Derner, 

James K. Detling and Michael F. Antolin, Front Ecol Environ 2006; 4(9): 459–464 

(copyrighted material that is reproduced by Liphatech with permission). 

Thank you for the opportunity to submit our public comment. 

Sincerely, 

Thomas Schmit 

Manager of Regulatory Affairs