Hot water (49°C [120°F] for 12 minutes)
has long been used as an effective treatment against insects
of quarantine significance on cut flowers and potted plants.
The DLNR Division of Forestry and Wildlife tree nursery in
Hilo and an agricultural engineer from the University of Hawai'i
at Hilo designed and built a hot water treatment facility
and did some testing to determine the lowest possible lethal
temperature for frogs that would also reduce incidence of
heat damage to treated plants.
Results indicated that a 45°C (113°F) treatment
for 3 minutes was adequate for killing frogs and their eggs.
Applied as a shower, this hot water treatment has been effective
on frogs and eggs in potted and landscape plants. Heat damage
to plants was reduced or eliminated by following the hot water
shower with 1-2 minutes of cool water. Orchids and
bromeliads were the only plants tested that were sensitive
to the treatment. Coqui frog eggs directly dipped in hot water
for 3 minutes had a lower rate of
hatching compared to untreated eggs of the same age.
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Treating coqui frog eggs in hot water
(113°F)
for 3 minutes reduces their rate of hatching.
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| Untreated eggs |
4 days after hot watertreatment
(113°F for 3 min, 1 min cooling)
(Note fungus beginning to engulf nonviable eggs) |
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| Hot water shower: |
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| a) Hot water system to disinfest tree seedlings of frogs prior
to planting (Division of Forestry and Wildlife, Hilo) |
b) Close-up of plants being showered for 5 min
with 113°F water followed by 1 minute of cool water. |
Photos by S. Chun and A. Hara, UH–CTAHR
A plant nursery constructed
a hot water shower container to disinfest potted plants of frogs
and eggs prior to shipment and sales. Various plant species
were treated at 113-115.6°F to determine their tolerance to
hot water. Treatment caused mortality of adult coqui frogs
and eggs in 10 minutes. This trial demonstrated that hot water
treatment is feasible and effective on a commercial scale. View
photos of the facility, process, and results.
All research on coqui
frogs reported here was conducted in compliance with the University
of Hawai`i Institutional Animal Care and Use Committee (Protocols
#02-029-3, 02-043-3, 02-028-3). |
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