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What’s that bug in my garden?

It’s a sweet potato 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.

sweet potato bug and egg cluster — Adult sweet potato bug next to egg cluster

Ramie Moth

The ramie moth is a destructive caterpillar that can completely defoliate native māmaki. This caterpillar was first discovered in November 2018 on Maui where it was destroying māmaki plants. Since then, it has spread to the Big Island and was found on the east side in November 2020. This is the first record of this pest in the United States. It’s known to feed on members of the nettle family (Urticaceae). Besides harming the māmaki plant, this caterpillar also poses a threat to the native Kamehameha butterfly as it competes for the same food resources.

The young ramie caterpillar will start by chewing holes in the middle of the leaf and create even larger gaps as they grow, leaving only the main veins. Kamehameha caterpillars start eating from the edge of the leaves. Young Kamehameha caterpillars will fold over the edges of the leaf to make a tent for protection.

Photo of Kamehameha caterpillar by Forest and Kim Starr

Adult ramie moth

Ramie Moth: appearance

Ramie moth (RM) eggs are about 1mm in diameter and are a clear-white color. The eggs are laid individually on the underside of leaves.Â Kamehameha butterfly (KB) eggs are more brownish in color. The first instar of RM caterpillars are green and black. As they get larger, they change color to become yellow and black with red/orange spots and thin white hairs. There is also a black variant of the RM caterpillar, but it still has the iconic red spots and white hairs. The RM caterpillar can look very similar to the KB caterpillar and they are found on the same plants, so it is important to make a positive identification before taking any action! Young KB caterpillars also have black-colored heads, but they turn green or brown as they get older.

Unlike KB caterpillars, the ramie caterpillars are aggressive…at least, relatively aggressive for a caterpillar! When disturbed the caterpillar may lift its head and start wiggling around, and might even vomit a green fluid. These actions are to dissuade predators but are not displayed by KB caterpillars.

The adult ramie moth is about 3 cm long with a 6-9 cm wingspan. It is mostly brown, with black markings on the scalloped wings. Hindwings have silvery-blue markings. They can be challenging to identify, so please send a picture of your suspect caterpillar to BIISC or your local HDOA or CTAHR office for identification.

Be careful when moving māmaki and olonā plants, and do not move them interisland. Always inspect your plants before moving them.

If you see a ramie moth caterpillar, please capture it and report it to 643-pest.org.

Ramie Moth HDOA Pest Report w/ pictures

How to ID a Kamehameha Butterfly

Mystery Invader Identified: Phenax hirtus

A critical part of the work we do at BIISC is looking for new, potentially damaging, arrivals, In late 2017, BIISC botanists collected a mystery plant on a trailside early detection survey on the Kona side near the Makaula-O‛oma State Forest Reserve. It was at first easy to overlook, with no eye-catching characteristics to make it stand out from the lush greenery around it. However, trail users had reported its aggressive tendency, and its persistence even after they tried to control it. The BIISC team realized that this plant did not match any known introduced or native species on the island, and observed that it was reproducing naturally – and quickly – throughout the area: an alarm bell indicating a potential invasive species.

However, before declaring a new species invasive, careful investigation must be done – and the first step is ensuring a definitive identification of the organism. But this seemingly simple question became more vexing as the team pored over botany records: just what WAS this plant? With hundreds of thousands of plants in the world, many with little published information available, plant ID is not an easy task. The team reached out to plant experts on the island and across the state, but no one recognized this one. Samples and photos made their way to various botanists until in 2020 a Smithsonian botanist, working with colleagues from Europe, was able to pronounce that a little-known, low-profile shrub from Central America, Phenax hirtus, had somehow arrived in Hawai‛i.

Phenax taking over the understory

Phenax leaves and growth pattern

Hogging Space

Like another recent invader, the Queensland Longhorn Beetle, Phenax hirtus wasn’t known to be a pest anywhere else in the world before it appeared on the Big Island. It is unknown how either arrived here, but most likely it was a “keiki form” (larvae in the case of the beetle, seed for the plant) as an accidental stowaway, quietly arriving in some kind of soil, plant material, or packing crate. These sleeper species will often quietly proliferate and spread, unnoticed until they begin to cause a problem. This can make it difficult to enact a successful eradication plan; without previous research, we don’t always know how to control the pest. Information about the species’ life cycle, reproductive strategies, seed viability, climate tolerance limits – all can be critical to making sure control efforts are effective.

Phenax hirtus has many of the classic characteristics associated with invasive plants: it is shade-tolerant and can grow in undisturbed vegetation, including under a native forest canopy. It has a climbing nature, able to pull itself up over other vegetation to seek light and space. It even finds a way to grow amongst aggressive Himalayan (kāhili) ginger – a known “space hog”! Seeds are tiny and can spread easily on wind or water.

Phenax hirtus overtaking residential landscaping. (Photo: JB Friday)

BIISC crews are working now to control outlier populations of Phenax in the Kaloko Mauka community where it was found and limit it from continuing to spread. Big Island residents are also being asked to be vigilant and take pictures of any suspect plants in other areas of the island. It is a nettle, the same large family as the native māmaki, so the leaves are similar, but generally skinnier and more green (not so much of the reddish veins that are generally present in māmaki). The best way to tell them apart: māmaki produces seeds in a distinctive fleshy white fruit at the end of the leaf node, while Phenax will have a dry brown ball of seeds.

Mamaki fruits (left) are fleshy and white, while Phenax fruits (right) are dry and brown. (Forest & Kim Starr; JB Friday).

In today’s world, some invasive pests are nearly household names in dozens of countries: Asian longhorn beetle, spotted lanternfly, red imported fire ants, giant hogweed. These pests make headlines the minute they appear in a new area. But Hawai’i, while at risk of these notorious invaders, is also uniquely vulnerable to taking a bad turn to invasive behavior. Life in Hawai’i evolved in isolation over millions of years, with a barrier of 2500 miles of open ocean dissuading colonization by new life forms. Biologists estimate that before human contact, a new species established in Hawai’i only about once every 10,000 years. Without the fierce biological competition and predation found on an African savannah or South American rainforest, our native species evolved without many of the defenses and protections that their continental counterparts had long developed.

The year-round temperate weather, novel native ecosystems with open niches, and multiple climate zones of the islands all provide opportunities for introduced species to become problematic in Hawai’i. With more introduced species reaching our shores today than ever before, it is critical to be vigilant and keep an eye out for anything new that appears unexpectedly, potentially posing a problem.

Mamaki leaves (left) tend to be more oval with reddish petioles while Phenax leaves (right) tend to be more narrow and green throughout. Photos: Forest & Kim Starr; JB Friday

Pampas Grass Eradicated

BIISC is happy to share some good news: one of the most notorious invasive grasses in Hawai‛i, pampas grass, has been eradicated from the Big Island! Both species of pampas grass known to occur in Hawaii, Cortaderia jubata and Cortaderia selloana, have been removed, and monitoring continues for any keiki that might appear at the sites of previous known locations.Â

Both species of pampas are on the state’s Noxious Weeds list. The South American plant was shipped around the world in the late 1800s, popular for the showy plumes used in fashion and decor. It grows in large clumps, with feathery white or lavender plumes growing up to 10 feet tall. As people planted it across the Pacific, it slowly began jumping from planting sites and spreading out into natural areas, disrupting native ecosystems in places like New Zealand, California, and here in Hawaii. It is now widespread on Maui, and because it is adapted to fire in its native range poses a significant threat as a fuel for wildfires.

Pampas grass is a noxious weed.

BIISC staff controlling pampas grass.

Efforts to eradicate pampas grass

When the Hawai‛i Island eradication effort began in 2007, the plant was mapped in over two dozen locations including several places in Volcano and on the West side of the island. Although most of the adult plants were removed early in the eradication timeline, Joel Brunger, our field operations supervisor, points out the challenges of surveying for other pampas grass clumps near an adult plant: each grass clump is capable of producing thousands of lightweight seeds which are carried by the wind as far as 20 miles from the parent plant!

BIISC relied heavily on reports from the public about potential pampas sightings, carefully tracking down and identifying each plant to locate any previously undiscovered populations. Removal of the plants by BIISC crews took time, as permission from property owners was required for most of the sites. Locating and contacting property owners can pose a significant challenge for our control efforts, but overall most people were cooperative and eager to support the removal of an invasive plant from their property. The Hawaii Department of Agriculture assisted with securing access for removal of the noxious weed where permission was difficult to obtain. Finally, in 2019, the last known population of pampas was removed, and native māmaki was planted in its stead. BIISC botanists continue to monitor the area to catch any keiki plants that may spring up.

An Ongoing Risk

Despite the razor-sharp leaves and potential for fueling wildfires, pampas grass is still sold throughout the world in the horticultural trade and used for landscaping. During the course of the eradication effort, BIISC developed the Plant Pono program, a nursery endorsement and education effort aimed at stopping the sale of invasive plants in Hawaii. Pono-endorsed nurseries voluntarily pledge to sell only non-invasive â€œponoâ€ plants. There have been no sales of pampas grass in Hawaii for the last several years, although seeds purchased online continue to be a risk for introductions of invasive plants.

If you spot an online seller promoting pampas grass and allowing shipment to Hawaii, pass the info along to us! Often, just informing a well-meaning grower outside of our state about the potential risks is enough for them to stop any shipment of the plant to the islands.

BIISC takes the lead on early detection and rapid response to new invasive plant species, which means our teams search for new species of plants on the island and target them for eradication when necessary and possible. Efforts to control many of our most notorious widespread invaders like miconia, albizia, or strawberry guava came too late, well past the time when it was economically possible to remove those species from the island. There is only a short window of time when an invasive species can feasibly be eradicated. Once that window has closed, control strategies switch to other efforts, like containment, or at the furthest point, exclusion only from high-value areas.

Currently, BIISC is targeting several invasive plant species assessed to be within the “window of eradication.” These species are not yet widespread, and BIISC crews are working to remove them now so that they will not become the albizia or miconia of the future. Visit our target species page to become familiar with our target species, and be sure to report any new or strange plants you encounter!

Pest Alert: Banana Lacewing

UPDATE: As of 2024 Banana Lacewing has been found on the Big Island.

The Hawai‛i Dept. of Agriculture has announced a new pest called the Banana Lacewing Bug (Stephanitis typica). This pest has a variety of hosts, not just bananas. As of June 2020, this lacewing has only been found on O‛ahu. Please report any new sightings to the Hawai‛i Dept. of Agriculture Plant Pest Control.

Hosts:

African Oil Palm (Elaeis quineensis)
Bananas (Musa spp.)
Camphor laurel (Cinnamomum camphora)
Cardamom (Elettaria cardamomum)
Champedak (Artocarpus integer)
Coconut (Cocos nucifera)
Colocasia sp.
Edible Ginger (Zingiber officinale)
Flowers (Alpinia spp.)
Heliconia spp.
Plantain (Musa x paradisiaca)
Soursop (Annona muricata)
Tumeric (Curcuma longa)

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