Citric acid was identified
by the Hawaii Dept. of Agriculture and the USDA Wildlife Service
as an effective, legal pesticide for coqui frogs. The U.S.
Environmental Protection Agency (EPA) considers citric acid
to be a minimum risk pesticide, and it is, therefore, not
regulated. The efficacy of citric acid was tested on coqui
frog eggs. Egg clusters or clutches (at least 4 days old)
were cleared of dead or infertile eggs and dissected into
two masses; one half was treated and the other half served
as untreated control. Treatments were 16% citric acid (1 ml
applied by aerosol) with no rinsing or rinsing one hour after
Egg clutches were
observed until all viable eggs hatched. Both treatments greatly
reduced hatch rate compared to the untreated controls. Two
of the 7 clutches that were not rinsed had some degree of
hatching, while 6 of the 10 clutches that were rinsed had
some degree of hatching. A solution of 16% citric
acid was 97% effective in decreasing coqui frog egg viability,
especially if the solution is not rinsed off.
using 25% citric acid were conducted on a variety of ornamental
plants. Palms and dracaena varieties were the most tolerant
of the citric acid.
citric acid kill only adult male coqui frogs?
conducted by USDA APHIS Wildlife Services, National Wildlife
Research Center and Hawaii Department of Agriculture in
Hilo showed that 16% citric acid solution killed nearly
100% of coqui frogs - including males, females with eggs
(gravid), juveniles, and eggs- upon direct contact Mortality
is based on contact with the solution, not the sex, age
or reproductive state of the frog.
pregnant female coqui frogs or eggs not affected by citric
female coqui frog lays eggs within hours of fertilization
by the male. Female frogs are therefore not considered
"pregnant". Females are no less susceptible
to citric acid than males; the most important factor is
direct contact with the spray.
frogs are unusual among frogs in that it is the male that
sits on the fertilized eggs until they hatch into fully
formed froglets approximately two weeks later. This
extraordinary amount of parental care helps to protect the
eggs from predators, disease, and dehydration, as well as
chemical sprays. Eggs are also laid in protected spots easily
overlooked when spraying. When eggs are not directly contacted
with citric acid, they can continue to develop and hatch.
sprayed with citric acid, but a few days later, I heard the
frogs again. Citric acid doesn't work.
people find frogs that remained alive in treated areas and
may conclude that treatment was ineffective, but it is more
likely that those survivors managed to avoid direct contact
with the chemical solution. Adult coqui frogs are about
the size of a quarter, and are capable of hiding in very
small cracks, under vegetation, and in crevices along rock
walls. If the citric acid solution is mixed or used
improperly, is washed away by rain or watering, or if frogs
do not come into direct contact with it, then effectiveness
sprayed once and haven't heard anything for several weeks.
We got them all, right?
you sprayed as soon as you heard a single male coqui frog
calling, you may actually be coqui-free after one application
of citric acid. If you waited until a chorus of many
calling coquis developed, then you most likely have a breeding
population of males as well as silent females, juveniles
and eggs. Since the egg hatching cycle is about 14 days,
we advise respraying every 2 weeks for several months in
conjunction with clearing vegetation and other debris in
which the frogs might take refuge and escape from the spray.
Also, prevent infestations by determining how the coqui
frogs got to your site in the first place - on plants from
another site? on a vehicle that went to a site with coqui
frogs? on lumber, tile or gravel? Get plants from
coqui-free sources or "quarantine" them in an
enclosed area, inspect them for eggs, juveniles and adults,
and listen at night for calling males before planting or
placing the plants in your yard.