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  Spray Citric Acid Solution

Spray commercially available citric acid on infested plants to kill coqui frog eggs, juveniles, and adult males and females. Citric acid is a common food additive and is considered safe for environmental use by the EPA. Citric acid (anhydrous, or dry powder) can be obtained in 50 lb bags or in repackaged 5 and 10 lb bags from chemical or garden supply stores. It must be first mixed with water to make a 16% (w/v) solution (1.3 lb citric acid per 1 gallon of water). (Note: 16% citric acid is now available ready-to-use as a premixed solution at most garden shops - check product label.)

Frogs are killed by direct contact with the spray and not by its residue.  For maxiumum effectiveness, spraying should be done following removal of dense shrubs and dead foliage to increase contact with the frog.  In landscaped or vegetated areas, spray in the early evening after a drizzle or heavy rain, when frogs start to call, rather than during a dry period or drought when frogs remain hidden and call less frequently. Moderate to heavy rain will dilute and wash away sprayed citric acid, so consult the weather forecast prior to spraying.  Thorough coverage of plants with the citric acid solution (including undersides of leaves where frogs may be hiding) is important. Spray or hand-capture frogs agitated by the citric acid that may jump out of the plants before they can find another hiding place.

Frogs that are not directly contacted during spraying may retreat and males may refrain from calling for a few days before re-emerging.  Spray again after two-weeks (time it takes for eggs to hatch) and monitor for calling males up to one year (time it takes for hatchlings to mature).

Citric acid may damage some sensitive plants, plants that are stressed, or young, growing plant parts, causing leaf spotting or yellowing. To avoid damage to delicate plants or flowers, thoroughly rinse the treated plants with fresh water to completely remove citric acid residue about an hour after spraying. Phytotoxicity (chemical damage) varies depending on exposure conditions. Pre-testing on a small section of a plant is always recommended. After spraying and/or rinsing, observe the section for a few days for discoloration before spraying a large number of plants or valuable plants.

(see Research section for a list of tested plants and photos of damage symptoms.

Follow all precautions on the Hawaii Department of Agriculture citric acid label. Click here to view or download the HDOA citric acid label.



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