Powdered corn cobs

DP Number(s): 394414

PC Code: 006154 cellulose

(corn cob doesn’t have PC code) EPA Reg. or File Symbol No:

84889-E

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

 WASHINGTON, D.C. 20460

OFFICE OF CHEMICAL SAFETY AND POLUTION PREVENTION/OFFICE OF PESTICIDE PROGRAMS 

MEMORANDUM

DATE: 4/25/12

SUBJECT: Science review of Rodetrol performance against rats and mice. The active 

ingredient in the product is powdered corn cobs, containing 45.1% w/w cellulose.

Decision Number: 447148

DP Number: 394414

EPA File Symbol Number: 84889-E

Chemical Class: Biochemical

PC Code: 006154 cellulose (corn cob doesn’t have PC code)

CAS Number: 9000-11-7 cellulose (corn cob doesn’t have CAS No.)

Active Ingredient: powdered corn cobs

Tolerance Exemptions: Non-food

MRID Numbers: 484335-05; 484335-17 to 484335-24, and 484335-39

FROM: Clara Fuentes, Ph.D. Entomologist

Biochemical Pesticides Branch

Biopesticides & Pollution Prevention Division (7511P)

TO: Leonard Cole, Regulatory Action Leader

Biochemical Pesticides Branch

Biopesticides & Pollution Prevention Division (7511P) 

ACTION REQUESTED

Rodetrol, LLC. is requesting registration of Rodetrol to be used as a rodenticide against rats and 

mice. In support of registration, the registrant has submitted summaries of product performance 
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studies in MRIDs 484335-17 in 484335-24, conducted on the same formulation under laboratory

conditions to support indoor use of the product.

RECOMMENDATIONS AND CONCLUSIONS

Product Performance: Acceptable. Sufficient information is provided in MRIDs 484335-17 to 

484335-24 showing that the proposed product kills rats and mice when fed exclusively on the 

product for a period of approximately 7 days for rats and 3 days for mice. The submitted 

efficacy data are summary of laboratory studies conducted on the same formulation under 

different trade names. The product causes physical disruption of the feeding mechanism in rats 

and mice. Mortality is caused by dehydration and malnutrition, however, several postulated 

pathological pathways were investigated and none were established as the physiological 

mechanism leading to these lethal outcomes. It is unknown how normal food consumption in 

addition to Rodetrol would have influenced product performance since the mortality effects of 

Rodentrol were tested by feeding the rodents exclusively on the product.

MRIDs 484335-39 and 484335-05 are supplemental.

Note to RAL: 

Label language restrictions concerning efficacy claims supported by data:

Experimental results correspond to experimental conditions of feeding caged rodents exclusively

on the product over different periods. In reality, free rodents are most likely to feed on 

additional food items so, the minimum periods for maximum efficacy reported on label and

supported by data are the outcome of artificial rather than real conditions. Therefore, it is 

uncertain whether the minimum period of 8 and 3 days for maximum efficacy on rats and mice, 

respectively, reflect actual performance of the product on free rodents. The label should clarify

that those measures of efficacy reflect ideal conditions and that optimal product performance

may differ under actual conditions of food consumption by free rodents. Due to the above 

explanation plus results from supplemental field tests in MRIDs 484335-39 and 484335-05, the 

word “control” should not be allowed on the label. Data indicates that the product reduces 

rodent population in infested areas but there is no conclusive proof that it kills 100% of free rats 

or mice infesting structures within 8 or 3 days, respectively. To test that, the researcher would 

have to conduct a different experiment designed to determine the optimal consumption level of 

Rodetrol in a mixed diet.

STUDY SUMMARIES

MRID484335-17: Efficacy of Eradirat against Sprague-Dawley laboratory rats and Assessment 

of mode of Action and Effects.
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The report is a summary of a lab test conducted to assess the effectiveness of the Eradirat in 

causing mortality inlaboratory rats, and to investigate its mode of action. Eradirat formulation is 

substantially similar to the proposed product, Rodetrol. The test organism was the SpragueDawley rat, Rattus norvegicus. Twenty two rats of equal sex ratio were acclimated for 2 weeks 

prior to study initiation. The rats were 6 weeks old when testing began. A group of 16 rats, 8 

males and 8 females, were fed Eradirat for 8 days in the absence of other food. A control group 

of 6 rats, half males and half females, were fed with rodent diet for the same time period. 

Consumption was measured daily. Body weight was recorded following treatment. Blood 

samples were collected daily and analyzed for haematological and biochemical paramaters used 

in clinical diagnosis. All rats fed Eradirat died within 6 days (ranging between 4 to 8 days) of 

treatment. Consumption of the product was low relative to consumption of rodent diet by rats in 

the control group. Treatment rats lost an average of 34.8% body weight following treatment 

while control rats gained 20.5% on average. Haematological analyses indicated elevated 

concentrations of red blood cells and haemoglobin, and decreasing concentrations of other blood 

parameters (mean cell volumes, white blood cells, and mean corpuscular haemoglobin. 

Biochemical analyses of serum samples indicated elevated concentration of other parameters in 

treated rats. Treated rats dehydrated and emaciated, with evidence of internal haemorrhage. 

Bladder contained no urine, and small intestine contained undigested solid material from bait. 

The researchers concluded that consumption of the bait caused dehydration through several 

proposed and unconfirmed mechanisms. Dehaydration triggers a cascade of physiological events 

that culminate in death by heart failure.

The report includes a list of references from the scientific literature. No information on animal 

husbandry and ambient laboratory conditions is provided. The report includes post mortem 

reports of pathology, and a couple of diagrams describing postulated lethal physiological 

pathways. Treatment means, with their associated standard deviations, for haematological 

parameters, body mass, food and water consumption are presented in graphs.

MRID 484335-18: Efficacy of Eradirat against Sprague-Dawley Rats

This is a laboratory study designed to determine the effectiveness of Eradirat in causing mortality 

in laboratory-reared Sprague-Dawley rat, Rattus norvegicus. The study is a duplicate of another 

study conducted by Celsis Laboratory Group (Kable, 2002) designed to meet the same objective.

Twenty four rats, half males and half females, 4 weeks old and weighing approximately 123 g. 

that ranged from 108 to 136 g, were received from Hercus Taeri Resource Unit in New Zealand, 

and acclimated for 7 days prior to test initiation. Rats were caged individually in rack-mounted 

cages of 1,400 cm2area. The animals were maintained at temperature of 21.6 C° ± 2 C°, RH 27-

48 % and light cycle of natural photoperiod. All rats were fed Purina Lab Diet and provided 

with water at libitum. Eighteen rats, half males and half females, were randomly divided into 

treatment and control groups. Twelve rats were assigned to treatment group, and 6 others to 

control (50:50 sex ratio). Treatment rats were fed exclusively on Eradirat until death of all rats, 

which took 5 days for the last rat in the treatment group. Control rats were fed Purina lab diet 

throughout the test period. 

The following parameters were measured to assess efficacy: mortality, behavior, body weight, 

food and water consumption, and pathology. Observations were recorded twice daily, in the 

morning and afternoon always at the same time. Body weights were recorded on days 1, 2, 4 and 

7 during acclimatization and at the end of study. Food and water consumption were measured 
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daily from third day of study initiation and always at the same time. All treated, plus one pair of 

male and female control rats were autopsied for determination of gross pathology. The data was 

analyzed by comparison of treatment means. Standard deviations of the means were reported. 

All rats died between 3.5 and 5 days.of daily feeding exclusively on Eradirat. The average for 

both sexes was 4 days. The time period between the first symptoms and death was 12 hours. 

The symptoms were piloerection followed by progressive lethargy and deteriorating 

coordination. At death, most rats had traces of blood aroud snout and urogenital area. There was 

no mortality or abnormal behavior among control group rats. All treatment rats experienced 20

to 25% weight loss while control rats increased their weights 10 to 20% in 5 days. Rats in 

treatment group showed an abrupt decline in food consumption of 5 to 7 g. while food 

consumption remained stable among controls, 20 g. for males and 15 g. for females throughout 

the test. The same trend was observed among treated and control rats regarding water 

consumption. Pathological examination revealed poor conditions among treated rats. Visible 

behavioral symptoms appear only at the final half day before death. The researchers concluded 

that the product caused rat mortality most likely from dehydration. The study reports a couple of 

minor deviations from the Celsis (Kable, 2002) study regarding rats mean body weights, 

controlled temperature and RH that are unlikely to compromise test results. Raw data are not 

included in the study report. The study report provides identification of the test substance as 

Eradirat, a pellet bait consisting of plant material with no conventional pesticides. 

MRID 484335-19: Confirming Effects of Eradirat on Rats when Fed ad libitum 

The study was conducted under laboratory conditions to confirmed the performance of Eradirat, 

formulation 3, on Sprague Dawley rats fed at libitum with the product for a period of 14 days. 

Test animals were individually caged and fed Purina Rodent Chow for 7 days acclimatization 

period. Animals were observed daily for general health, food consumption. Twenty and 10 

healthy rats (50:50 sex ratio) were randomly assigned to the treatment and control groups, 

respectively. Rats age are not reported. Initial weights ranged from 115 to 132 g. in females, 

and 99 to 123 g. in males. Observations included food and water consumption and body

weights, recorded daily. Clinical and behavioral observations were recorded twice daily. Dead 

or euthanized rats were examined for gross necropsis. Results show that all 20 rats died in the 

treatment group after 5 days of treatment. Only data summaries are reported. Treatment means 

were not subject to statistical analysis for comparison. 

MRID 484335-20: Efficacy of Eradimouse against Norway Rats

This is a laboratory study to assess the effectiveness of Eradimouse against non-acclimatized 

feral Norway rats; specifically, the project is designed to investigate the mode of action of the 

product through pathological observations and microbiological cultures. It is postulated that 

certain type of bacteria might be involved in the cause of death. In particular, Clostridium 

perfringes was identified by Coerze (1999) as a possible mortality agent. The test material used 

was Eradimouse, ‘formulation 3,’ which is the same formulation as Eradirat in smaller pellet. 

Wild-trapped rats were caged in 1,400 m2 metal cages in the lab and kept at 20 to 25 C°, RH = 

30 to 35 %, and natural summertime photoperiod. Twenty five wild rats were brought into 

captivity but not acclimatized before testing to avoid the possibility that key intestinal bacteria 

may be lost during acclimation to the sterile conditions of the laboratory environment. Twenty 
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rats were randomly assigned to treated and control groups. The treatment group consisted of 20 

rats, 12 males and 8 females. The control group consisted of 5 rats, 4 males and 1 female. 

Treatment rats were fed exclusively on Eradimouse while control rats were fed on rodent diet 

pellets. Daily food consumption was estimated to the nearest 0.1 g. from the weight of food 

remaining after each 24 hours period. Body weights were recorded at beginning of trial and on 

death or end of testing. Doses of ingested product were calculated dividing total consumption 

(corrected for weight changes in control samples) by mean values of beginning and ending body

weights. Post-mortum examination was conducted for gross pathology and bacterial cultures. 

Sixteen rats died after consuming doses from 0.05 to 0.34 g of product/g of body weight. There 

was no mortality among control rats. Control rats consumed on average five times more food 

than treated rats. Wild rats showed considerable variability in their susceptibility to the 

Eradimouse. Blood loss from the stomach was the only consistent symptom. Gross pathology

and intestinal micro-organisms were normal. Eradimouse killed most rats in less than 14 days, 

approximately within 5.6 days of treatment. On average, treatment rats weighed less than 

controls (start weight of treated rats = 153 ± 15.1g., n = 20; start weight of controls = 203.6 ± 

22.6 g., n = 5). Average final weight among treated rats = 121.9 ± 12.8 g. Average final weight 

among controls = 237.3 ± 26.7 g. On average, treated rats lost 21.4% of their initial weight by 

the end of the trial while controls gained 10. 9% by end of trial. Average food consumption 

among controls was 169.2 (average dose = 0.75 g/g). Average food consumed among treated 

rats was 18.7 g (average dose = 0.14g/g). Minimum lethal dose ranged from 0.2 to 0.3 g/g b.w. 

The lethal mechanism of the product remains unclear. Rats ate very little of the product and loss 

considerable weight. Use of wild rats did not result in unusual proliferation of intestinal bacteria. 

MRID 484335-21: Efficay of Eradimouse against Wild House Mice

This is a laboratory study to assess the efficacy of Eradimouse pellets against wild house mice, 

Mus musculus; specifically, the project is designed to investigate the mode of action of the 

product through pathological observations and microbiological cultures. It is postulated that 

certain type of bacteria might be involved in the cause of death. In particular, Clostridium 

perfringes was identified by Coerze (1999) as a possible mortality agent. Thirteen wild caught 

mice were acclimatized for 4 weeks in captivity. Mice were caged individually in 1,400 cm2

area cages and maintained at temperature ranging from 20 to 25 °C, RH = 30 – 50%, and light 

cycle of natural summertime photoperiod. All mice were fed on standard rodent diet during 

acclimatization period. Ten mice, half male and half female, were randomly assigned to the 

treatment group and fed exclusively on Eradimouse for 14 days trial. The control group 

consisted of 3 female mice fed on rodent dietary pellets throughout the trial. Daily food 

consumption was estimated to the nearest 0.1 g. from the weight of food remaining in feeding 

containers every 24 hours. Body weights were recorded at beginning of trial and at the end. 

Doses of ingested product were calculated dividing total consumption (corrected for weight 

changes in control samples) by mean values of beginning and ending body weights. Postmortum examination was conducted for gross pathology and bacterial cultures. Mortality was 

100% among treated mice. The lowest lethal dose was 0.3 g/g body weight. There was no 

mortality among the control mice. On average, control mice consumed about 3 to 6 g. of food 

daily while treated mice consumed approximately 1 to 3 g of product daily. Treated mice lost 

28.8% of body weight in around 3.8 days from beginning of trial while controls lost 5.5% body

weight over 14 days since test initiation. The lethal mechanism of the product was not 
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established without indication of Clostridium perfringes as a possible mortality agent.

MRID 48433522: Effects of Eradimouse on Mice when Fed ad libitum

The study was conducted under laboratory conditions to confirm the effectiveness of the product 

to cause mortality on lab-reared mice, Non-Swiss Albino, fed on the product for 14 days. 

Ambient laboratory conditions are not reported. The report indicates that the animals were 

maintained according to the Guide for the Care of Laboratory Animals (NRC, 1996). Twenty 

mice, half male and half females were randomly assigned to the treatment group. The control 

group consisted of 10 mice, half males and half females. Treated mice were fed exclusively on 

the product while control mice were fed Purina Rodent Chow throughout the test. All mice were 

individually caged and fed on certified Purina Rodent Chow for 7 days prior to beginning of 

testing. During the acclimatization period, food and water consumption were monitored daily. 

All mice were observed daily for health and suitability to testing. After the acclimatization 

period, the initial body weight of female mice ranged from 24 to 30 g. and from 26 to 32 g. for 

males. Feed and water consumption were estimated daily throughout the test period. From day

1 to day 7 of testing, mice were observed towice a day for pathological and behavioral 

symptoms. From day 7 of testing, control mice were observed once daily. Body weight was 

recorded daily. Post-mortum examination for gross necropsy was conducted on all mice at the 

end of the test. No Microbiology or histology was performed for this study. Death occurred 

within 7 days among treated mice. Necropsy observations were normal among test and control 

animals. Data on body weights, food and water consumption, were summarized and tabulated. 

No statistical analysis for comparison of treatment means is reported. 

MRID 484335-23: Efficacy of Eradimouse against Feral House Mice

The test was conducted in the laboratory to assess the efficacy of Eradimouse against feral house 

mice, Mus musculus, and investigated the mode of action of the product through pathological 

observations and microbiological cultures. Thirteen wild trapped mice were acclimatized to 

captivity for 4 weeks. They were individually caged in 1,400 cm2area cages at ambient 

controlled temperature ranging from 20 to 25 °C, RH = 30 to 50%, and natural summer time 

photoperiod. Ten mice, half male and half female, were randomly assigned to the treatment 

group. The control group consisted of 3 males. Treated mice were fed exclusively on the 

product. Control mice were fed rodent dietary pellets. The trial lasted 14 days. Daily food 

consumption was estimated daily from the weight of food remaining after each 24 hour period. 

Body weights were recorded at beginning and end of trial or upon death. Doses of product were 

estimated by dividing the total consumed (corrected for weight changes in control samples) by

the mean value of beginning and ending body weights. Two dead mice from treatment group 

were submitted to post-mortum examination for gross pathology and bacterial cultures from the 

upper and lower intestine. Mortality was 100% among treated mice. The lowest lethal dose was 

0.3 g/g body weight (about 6 g/20 g body weight). There was no mortality among controls. 

Control mice consumed an average of 3 to 6 g of food daily. Treated mice consumed an average 

of 1 to 3 g of product per day. Control mice lost an average of 5.5 % body weight during 14 

days of trial. Treated mice died around 3.8 days post treatment, and lost 28.8% body weight. 

Cause of death was not established. 
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MRID 484335-24: Trials to Support Registration of Rode-Trol Time to Death Efficacy (Rats 

and Mice)

This is a laboratory test conducted on rats and mice to determine the time it takes for the product 

to cause mortality in rats and mice when fed exclusively Rodettrol followed by rodent food 

pellets.

The species of rats tested was Ratus norvegicus obtained from lincesed supplier Harlam, USDA. 

The mice were not derived from a specific strain, and no information is provided about their 

source. The same husbandry procedures were followed for rats and mice. Only healthy young 

adult rats, never tested before, were selected for the experiment. Their initial weight ranged from 

115-125 for males, and 115-125 for females (± 20% of average weight). Upon their arrival to 

the test facility, the rats were paired with others of the same sex, and assigned to clean stainless 

steel wire mesh cages in a temperature controlled room. No information is provided on the size 

of the cages or ambient conditions such as temperature, light cycle, and relative humidity. 

The rats were allowed to acclimate to the testing facility for 10 days prior to test initiation. The 

control group was fed Purina rodent feed (guinea pig pellets), and the experimental group was 

fed on Rodetrol Rat pellets. Water was available at libitum. The experimental design is 

described as having 5 treatments, replicated 4 times. Each replicate consisting of 2 cages, each 

cage containing 1 pair of male and female rats per cage for a total of 16 rats (8 males and 8 

females). The total number of male and female rats employed in the experiment was 80; 40 of 

either sex. Treatments from 1 to 5 differ in number of days rats were fed Rodetrol. Rats in 

treatment 1 were fed Rodetrol for 6 days. Rats in treatments 2, 3, 4, and 5 were fed Rodetrol 

daily for 7, 8, 9 and 10 days, respectively. There were 2 controls. One control was fed Purina 

rodent pellets, and the other was kept unfed. Observation lasted for 20 days.

The same experimental procedure was conducted on mice weighing approximately 30 grams (± 

10%) at beginning of the experiment. No information is provided on the source of the mice, 

their age or health status. Each experimental and control group was replicated 4 times as 

described on the above paragraph. Each replicate consisted of 1 cage housing 1 pair of same sex 

mice per cage. As described, individual pairs of same sex mice per cage were randomly assigned 

to each treatment replicate for a total of 8 mice (4 of either sex) per control treatment.

Experimental treatments 1, 2, 3, 4, and 5consisted of mice fed daily on Rodentrol for 1, 2, 3, 4 

and 5 days, respectively.

Results are tabulated on separate tables for time to death for rats and mice. Rat mortality was the 

highest, around 100%, at treatments 3, 4, and 5 for rats fed daily on Rodetrol for 8, 9 and 10 

consecutive days. There was no mortality among control rats fed on Purina rodent pellets. 

Mortality was 50% among unfed control rats. 

Experimental and control mice show the comparable results. Mortality was the highest, around 

100%, at treatments 3, 4, and 5 for rats fed daily on Rodetrol for 3, 4 and 5 consecutive days. 

There was no mortality among control mice fed on Purina rodent pellets. Mortality was 50% 

among unfed control mice. 
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The researcher concludes that Rodetrol induces mortality in cage rats and mice over time of 

consecutive feeding exclusively on the product. It takes a minimum of 8 and 3 days of 

continuous feeding to induce mortality in rats and mice, respectively. 

cc: Clara Fuentes, RAL , BPPD Chron File, IHAD/ARS

FT, PY-S: 4/25/12
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