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Ants in Hawaiʻi

As the most isolated island chain on Earth, for most of its existence Hawaiʻi was too distant for all but a very few plants and animals to colonize. But when people discovered the islands, the rare naturalization event – only once every 10,000 years – soon turned into a near-daily occurrence. Although many plants and vertebrates were brought intentionally by humans, insects were mostly accidental travelers, stowing away on other cargo. Humans like to move stuff, and sometimes, that stuff carries ants! Hawai’i evolved with no native ants, and the 60+ species that now call the islands home are all considered pests. The more aggressive species in particular can have significant impacts on the environment, by reducing biodiversity (they chase other insects away), harming native animals like birds and sea turtles, and increasing the number of plant pests, like aphids and mealybugs. As most home gardeners already know, ants and plant pests go hand in hand. Certain families of Hemipteran insects produce honeydew, a sugary substance high in carbohydrates. Many species of ants “farm” these insects, including aphids, mealybugs, whitefly, and other garden nuisances. As the population of these pests increases, so does the amount of sooty mold and plant disease.

Little Fire Ants and Hawaii Ant Lab

When little fire ants made it to Hawai’i, there were no protocols in place for treatment. To combat this new invasive ant, the Hawaiʻi Ant Lab (HAL) was created in 2005. This team of researchers and technicians began testing various products to target LFA, making sure that the baits were attractive enough for the ants to pick up, but deadly enough to accomplish the goal. One immediate challenge was using granular bait products in east Hawaii’s notoriously damp environments, full of heavy vegetation- the products didn’t reach high up into the trees where ants were making colonies, and they quickly decomposed in wet conditions, becoming ineffective. HAL researchers created an innovative solution: a goopy “gel mix” that combined attractive oil and protein with pesticides. It was water resistant and able to be sprayed high into the trees where the LFA were living. They continue to test ways to improve the gel bait, and just last year published a recipe that could be used with Advion WDG, a new product easily available online.

HAL also tested dozens of granular products, ruling out those that weren’t effective or attractive to LFA and sharing their findings with Big Island residents. It’s not just working with ants, either – adding pesticides to the approved list in Hawai’i means a lot of red tape, and HAL does the paperwork too! They collaborate with manufacturers and the HDOA’s pesticides branch to navigate regulatory hurdles, applying for special licenses and making products available to Hawai’i consumers.

As LFA expanded their range across Hawai’i, so has HAL. On all the islands where LFA populations have been discovered, HAL staff have collaborated with HDOA and ISC personnel to survey, map, treat, and monitor LFA populations.

While little fire ants are a literal pain, there are even worse ants out there! HAL is a part of the HISC’s Māmalu Poepoe program, which monitors ports for highly invasive insects that are spreading around the world. Some of the ants that HAL looks for at ports are the red imported fire ant and the tawny crazy ant.

Red Imported Fire Ant – Tawny Crazy Ant

Solenopsis invicta (red imported fire ant, or RIFA) are larger reddish ants that act aggressively when their nests are disturbed. Unlike LFA, they like to build their nests in the ground by making large dirt mounds. RIFA has been spreading across the southern US stinging thousands of people and livestock along the way and has caused deadly reactions in humans and pets. They have been recorded spreading in potting media, sod, soil, and used electronic equipment. Besides stinging people and animals, RIFA will also chew on crop plants, damaging them and reducing yields.

Nylanderia fulva (Tawny crazy ant) is a small, fast-moving ant that is spreading quickly through the United States. Similar to LFA, they breed quickly and produce multiple queens, creating large supercolonies. While they don’t sting, they excrete formic acid, which can be very damaging to wildlife. In badly infested areas they have killed chickens and blind cattle. They also can destroy and short-circuit electrical equipment. Tawny crazy ants are easily transported by mistake because they will make their nests in almost anything.

These are just a few of the ants that have Hawaiʻi Ant Lab’s attention. Help us detect new ant species by collecting ant samples on your property and sending them in to get identified. Ants are small and require a microscope to properly ID, so take advantage of the free identification services available at BIISC and HAL. Request your FREE ant collection kit today from www.stoptheant.org.

Learn more about ants by visiting the Hawaii Ant Lab website and follow them on social media:

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What’s that bug?

Throughout the late winter and early spring, you may notice an odd looking bug in your garden. Although a healthy garden will draw many critters (some beneficial, and some not), this one stands out: it’s on the large side at nearly 1 inch long, with noticeably large “thighs”. You’ve spotted a sweet potato bug (Physomerus grossipes)! This is a type of true bug in the Coreidae family, or leaf-footed bugs. Members of the Coreidae have enlarged showy parts on their hind legs – these guys do not skip leg day.

If you’re a sweet potato grower or neighbors with one, then this is probably an unwelcome guest. Generally however, sweet potato bugs are considered a minor agriculture pest and are not dangerous to humans or animals.

Characteristics

• Adults are approximately 1 inch long
• Brown grey mottled color
• Wings fold over each other at the end of the body making a dark colored diamond
• Orange lines along the edge of the body
• Large distinct ‘thighs’
• Like to cluster together in large numbers

Impact

This insect has a piercing mouthpart that is used to suck sap from leaves of their preferred food plants, members of the morning glory family (like sweet potatoes) and legumes. One or two insects won’t harm the plant, but a large number of them will cause leaves to yellow and wilt. Even when under attack by a huge number of sweet potato bugs it’s likely that the plants won’t completely die, but the attack will reduce plant production and leave it susceptible to other insects and diseases. The bugs can often be found resting on other plants, but this does not indicate feeding.

Photo: Alistair Bairos

Treatment

Sweet potato bugs are rather resilient and most insecticides are ineffective on them. The best method for removal is to simply pluck the bugs off the plants and dunk them into a container filled with soapy water. Their clustering habit makes them easy to collect in large numbers. They are docile and can’t bite, sting, or release stink smells, so hand capturing them is non-hazardous and the most effective method to protect your sweet potatoes. While your picking away at the adult insects don’t forget to smash any egg masses you may also come across.