CONTROL OF COQUI FROG POPULATIONS IN HAWAII

• Sponsoring Institution: State Agricultural Experiment Station
• Project Status: TERMINATED
• Funding Source: STATE
• Reporting Frequency: Annual
• Accession No.: 0194237
• Project No.: HAW00528-1013S
• Project Start Date: Oct 1, 2002
• Project End Date: Sep 30, 2005

Project Director
Ako, H. M.

Recipient Organization
UNIV OF HAWAII
3190 MAILE WAY
HONOLULU,HI 96822

Performing Department
MOLECULAR BIOSCIENCES & BIOSYSTEMS

Non Technical Summary
Coqui frogs are reproducing rapidly in Hawaii because they lack natural predators. Their levels are about ten times the levels in their native Puerto Rico. They disturb the sleep of residents and visitors and may put endangered bird species at risk by competing for food insects and serving to raise populations of rats and mongooses which are predators of both frogs and native birds. The purpose of the project is to control coqui frog populations through use of pesticides. Part of the problem is to understand the biochemical mode of action of pesticides.

Animal Health Component

100%

Research Effort Categories

Basic

30%

Applied

70%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
135	0860	1150	30%
135	3899	1000	70%

Knowledge Area
135 - Aquatic and Terrestrial Wildlife;

Subject Of Investigation
0860 - Endangered species; 3899 - Other animals, general;

Field Of Science
1150 - Toxicology; 1000 - Biochemistry and biophysics;

Keywords

frogs

hawaii

invasive species

pesticides

amphibia

pest control

wildlife population

extracts

pyrethroids

toxicology

ova

coffee

hot water

lime

eleutherodactylus

non target organisms

performance evaluation

nicotine

trifluoromethyl nitrophenol

reptiles

mode of action

pesticide metabolism

Goals / Objectives
1) Determine whether laboratory studies using pyrethrins and culled coffee bean extracts are efficacious in the field. Initiate toxicology on coqui frog eggs. Hot water and hydrated lime treatments will be tried in another project. 2) Along with this, determine the effect of pesticide treatments on non-target species. 3) Explore whether other potential pesticides are cheaper and/or more efficacious on Eleutherodactylus including, 3-trifluoromethyl-4-nitrophenol, other pyrethrins, and nicotine. 4) A larger scope objective is to develop a larger data base on amphibian and reptile toxicology. 5) Understand the biochemistry and physiology of caffeine and pyrethroids as much as possible including the reasons they are selectively toxic to target species. 6) Work with local growers to assess possible issues with phytotoxicity and with local communities to assure as much as possible that control methods are sustainable and self-starting over time. Obtain time frames for re-treatment.

Project Methods
1) To determine whether laboratory studies using pyrethrins and culled coffee bean extracts are efficacious in the field, conduct field trials. Initiate toxicology on coqui frog eggs to see whether eggs are killed too. Current lab work has been very promising. Current results suggest that Pyronyl Crop Spray and culled coffee bean extracts give a 100% kill rate after a single application. All field trials would require that population estimates be done both before and after any treatment to determine the efficacy of spraying. Noise levels generated by the frogs and its reduction will also be measured. 2) Along with this, determine the effect of pesticide treatments on non-target species. Preliminary results indicate that caffeine kills introduced species of toads, insects and lizards (Campbell, manuscript in preparation). Such results are very promising for other alien pest species. 3) Explore whether other potential pesticides are cheaper and/or more efficacious on Eleutherodactylus including, 3-trifluoromethyl-4-nitrophenol, other pyrethrins, and nicotine. These will be tested in the laboratory initially. 4) A larger scope objective is to develop a larger data base on amphibian and reptile toxicology. While there are academic studies using frogs as model species, we have been unable to find studies on the control of amphibians or reptiles. Moreover, we have only been able to find pyrethrin studies. The literature is silent-as far as we can tell-on caffeine toxicology. 5) Understand the biochemistry and physiology of caffeine and pyrethroids as much as possible including the reasons they are selectively toxic to target species. We intend to use antagonists to elucidate the mode of action of caffeine and pyrethrins. These would include curare, succinyl choline, dantrolene, ryanodyne, verapamil and so on. Determination of caffeine levels in the blood at various times after treatment should yield useful information as to its catabolic breakdown to clarify its role as a toxin. Glycogen, blood glucose, and blood lactate levels will be measured to see whether the toxicity of caffeine may be a simple metabolic one. The pyrethrins may be a stressor. Caffeine may be a metabolic stressor by increasing cAMP levels, which may turn on lipid and glycogen mobilization. Frogs may be overstressed and killed by hypoglycemia. 6) Work with local growers to assess possible issues with phytotoxicity and with local communities to assure as much as possible that control methods are sustainable and self-starting over time. Obtain time frames for re-treatment.

Progress 10/01/02 to 09/30/05

Outputs
Coqui frogs are a nuisance in Hawaii emitting loud shrieks keeping residents awake at night. Also, they threaten the potted plant industry because they often hide away in plants and recipient importers threaten banning Hawaii plants. Field trials with 1% caffeine and 0.1% pyrethrin were completed. These trials were conducted at night when the frogs emerged from cover and showed that caffeine/pyrethrin decreased frog populations more than 80% if frogs were counted before and a day after spraying. Something may be wrong with the counting method because the expected numbers of carcasses were not found after spraying. However, the experiment also revealed that frog numbers were not as high as reported in the literature. Laboratory work revealed that caffeine acted as a cAMP phosphodiesterase inhibitor and that it was active in doses at which it is toxic to humans and rats when delivered orally.

Impacts
Caffeine and pyrethrin are as toxic to humans and rats as they are to coqui frogs. Energy should be diverted to other control methods.

Publications

• No publications reported this period

Progress 10/01/03 to 09/30/04

Outputs
Caffeine and pyrethrin were tested against coqui frogs in the laboratory. It was found that 2% caffeine gave complete kills. Pyrethrin, used at 0.02% concentration, was not toxic. It paralyzed coqui frogs, however. Together caffeine and pyrethrin used at 1% and 0.01% were completely toxic. Biochemical tests showed that these raised blood glucose levels about five fold. This led to lowering of muscle and liver glycogen but it was felt that high blood glucose (hyperglycemia) was the cause of the toxicity probably acting as a phosphodiesterase inhibitor preventing the degradation of cAMP. This was supported by use of a known analog of caffeine, 1-isobutyl-methyl xanthine which caused the same biochemical and toxic effects on coqui frogs. Action via muscle calcium gates was excluded by noting that muscle relaxers that work on the ryanodyne receptors do not protect against caffeine toxicity. Toxicity via hypertension was excluded by noting that angiotensin converting enzyme inhibitors were without effect. It was concluded that caffeine is effective in coqui frogs in exactly the same way as it is for humans and therefore should not be considered as a practical pesticide. Fieldwork trials were nonetheless initiated to test field methods using a pesticide mixture of known toxicity.

Impacts
The project determined that caffeine and pyrethrin should be abandoned as practical pesticides directed against the coqui frog but may lead to rational targeting of amphibian pests directed by biochemistry. A contribution may be made in the future in the field trial methods area.

Publications

• No publications reported this period

Progress 10/01/02 to 09/30/03

Outputs
Demonstrated that culled coffee beans are not an economical source of caffeine for coqui frog control. Found that a 1% caffeine/0.01% pyrethrin cocktail is very potent in killing coqui frogs and should be tested further. Elucidated the mode of action of caffeine (cAMP phosphodiesterase inhibition) and found that it is synergistic with pyrethrin.

Impacts
Caffeine/pyrethrin is another potential controlling agent for coqui frogs. The chemicals are the most potent of those being investigated. Research has been done so that the chemicals may be applied at a rate of up to 70 lower than previously estimated. This is proportional to cost of application.

Publications

• No publications reported this period

Progress 10/01/01 to 09/30/02

Outputs
No progress to report. This project was initiated on October 1, 2002.

Impacts
(N/A)

Publications

• No publications reported this period