Alex asks: I have not heard any coqui frogs on my property for several months. I thought we had got rid of them all. Now I am hearing them again. I want to get rid of them. What’s the latest advice on coqui control?
Tropical Gardener Answer: Coquí is the common name for the small frogs Eleutherodactylus coqui. Most coqui frogs hibernate when the weather gets cool and dry. Here in Kona we’ve had a cool, dry winter but spring has sprung. We are now having more frequent rain and warmer weather. These are ideal conditions for male coqui frogs to come out of hiding and start chirping to attract a mate.
Though the coqui mating call has become white noise for some of us, others may find it extremely annoying. Just know that the presence of coqui frogs can negatively impact the value of your property if you are considering selling.
It’s not only the annoying chirping that makes these frogs undesirable. Recent studies have shown that large coqui infestations can consume more than 50,000 insects in a single night. This can cause population declines in bees, other pollinators and beneficial as well as native Hawaiian insects. Endemic birds and native fauna that rely on these insects for food are also threatened by expanding coqui populations.
Studies in large coqui populated areas also show a 19 percent increase in mosquito populations. A plan to reduce the number of coqui frogs in your area is a very good idea.
Female coquis do not call. They find mates and proceed to lay as many as 1,500 eggs a year. The males become calling adults in about eight months and usually stay in one place chirping until a female comes to them to mate. Once she lays her eggs, the males stay put and guard them while the females continue roaming. Coquis can live up to six years. A heavily infested acre can contain as many as 1,600 frogs at one time, half of which might be calling males. That’s a lot of noise. Get started controlling their population now before it gets to that point.
Begin your coqui control plan by eliminating habitats that frogs like. During the day coqui frogs usually find a moist place to hide. They might stay under leaf litter, in empty pots or in wood piles. Remove dead leaves, prune and thin shrubs, and clear debris under plants to reduce frog habitats. Dispose of green waste by composting or mulching. Moving and inspecting these sites can uncover frogs and eggs. Since hot water, citric acid solutions or baking soda can kill frogs and eggs on contact, you can treat these areas and hopefully kill any hiding frogs.
Though the first coqui frogs to arrive in Hawaii from Puerto Rico were about the size of a dime, newer generations have gotten larger. They are now about the size of a silver dollar. Their light brown coloring and increased size distinguishes them form the smaller, innocuous greenhouse frog which is gray or brown with black spots.
After emerging from daytime hiding to feed at night, coquis usually find a perch in some vegetation and start calling for a mate. Since they can hide very well in crotches of trees or leaf joints of palms, ti plants and bananas, locating them can be difficult. They also are sensitive to sound and will stop calling or throw their call in another direction when they hear you approach.
Before you head out for the hunt, you’ll want to arm yourself with the weapons of coqui destruction. Both iPhones and Androids have coqui apps available. Since the males will call in response to hearing another coqui, these apps can really help you find frogs. Once you have the male frog calling in response to your phone, you can generally get close and, if you have a head lamp or flashlight, you can often watch them puff out their throats and chirp. It is best to approach them from the front as they can only jump forward or sideways to escape.
Citric acid is the only chemical approved for commercial coqui control. Anecdotal reports claim that baking soda is equally effective but you should only use it on your own property. These substances burn the frog on contact and it will usually die in a few minutes.
For general control, a 16% citric acid solution will work. To make it, mix 1.3 pounds of citric acid powder with a gallon of water and spray it thoroughly into the vegetation of infested areas. Citric acid is safe for most plants, though it may burn sensitive orchids and ferns. If it does get on sensitive plants, rinse them with water thoroughly within an hour of spraying.
Hot water between 113 and 115 degrees will also kill frogs and eggs. You can use this treatment on potted plants, just be sure not to use water hotter than this or it will damage the plants. Follow the treatment with a minute of cold water to cool off the plant.
You can also carry baking soda powder when hunting frogs. It is advised to wear protection for your skin, eyes and nose when using either baking soda or citric acid.
If you decide to catch the frogs, you can kill them humanely by freezing. Place them in a sealable container with air holes in the lid and put it in the refrigerator overnight. The frogs will become comatose in the cold temperature. Then move the container to the freezer for 2 or three days. The freezing temperature should kill them.
UH CTAHR has several free publications you can view or download online. For general information and some good links go to https://www.ctahr.hawaii.edu/coqui. For control in nurseries go to https://www.ctahr.hawaii.edu/coqui/documents/PosterAHaraFICCF.pdf and to learn how to trap coquis refer to the publication at https://www.ctahr.hawaii.edu/oc/freepubs/pdf/MP-5.pdf.
Good luck dealing with your coquis. Don’t wait to go after them. as the early hunter gets the frogs — and by doing so, prevents reproduction.
Email plant questions to firstname.lastname@example.org for answers by Certified Master Gardeners. Some questions will be chosen for inclusion in this column
Diana Duff is a plant adviser, educator and consultant living in a dryland forest north of Kailua-Kona.
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Wednesday: “Coffee Berry Borer Conference” from 8 a.m. to 4 p.m. at the Courtyard by Marriott King Kamehameha’s Kona Beach Hotel, 75-5660 Palani Road. An informative day of sharing current knowledge of this pest and the latest management practices. Free and open to the public. Hosted by the Coffee Berry Borer Areawide Program (USDA-ARS and CTAHR). For more information and to register, visit http://cbbconference.eventbrite.com.
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Farmer Direct Markets
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“Kamuela Farmer’s Market” from 7 a.m. to noon at Pukalani Stables
“Waimea Town Market” from 7:30 a.m. to noon at the Parker School in central Waimea
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Sunday: “Pure Kona Green Market” 9 a.m. – 2 p.m. at Amy Greenwell Garden in Captain Cook
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