Queensland Longhorn Beetle
NOTE: QLB has only been found in the Hilo side of the Big Island. Please report if found in other places on the island.
The Queensland Longhorn Beetle (Acalolepta aesthetica) was accidentally introduced to Puna, Hawai‛i likely through imports from Australia. Larvae tunnel through wood, weakening it and disrupting the plant’s ability to transport nutrients and water.
Larvae develop into adults within the wood and can emerge even from cut trees; chipping wood will prevent emergence. Do not move unchipped wood to noninfested areas.
There is still a lot unknown about QLB. We are not sure how long their life cycle is or how long they can live in the wood before pupating into an adult. Researchers on the Big Island are constantly learning more about QLB.
Description:
- 0.75 in to 1.8 in. long
- Brown, velvet-like appearance
- Long antennae (1-2x body length)
- No patterns or spots on body
- Two spines on its ‛neck’
- Hisses when disturbed
What to look for:
- Sawdust-like frass coming out of holes in trunk
- Oozing sap from damaged area
- Perfectly round exit holes
- Girdling on trunk or bark lifting
- Branch die-back and dropping
Integrated Pest Management for QLB
The Queensland longhorn beetle is still a relatively new pest and not much is known about it. Because of this we are still trying to find the best way to control them. Just like any other pest there are multiple things we can do to try to control the population and protect our crops.
Deterring Adult Beetles
An important step in protecting your trees are to try to prevent an infestation before it begins. When a female beetle lays and egg she tests the bark first by biting it. There are a few things you can add to your bark to deter the beetle before she lays her egg.
These methods are still in the research stage and have not undergone field trials yet. When trials are complete we will update the results.
- Kaolin Clay (Surround WP)
- Tree wrap
Both products have shown to deter beetles in lab trials. The tree wrap works well but it can be very time consuming to put on, best only if you have one or two trees.
Latex paint DOES NOT WORK. And mixing latex paint with neem oil can cause a chemical reaction that can damage your tree.
Catching Adult Beetles
Recent studies have shown that the adult beetles are nocturnal and spend most of the day hiding. In a short study by Dr. Matt Siderhurst, he found that QLB don’t seem to travel very far from the trees. They often are hiding in leaves right at the base of the tree. They also seem to be slightly attracted to lights at night.
While this is not the most effective method, removing any adults from the environment can help lower the population.
QLB are bark eaters so they do have a pretty hard bite!
Treatment for Queensland Longhorn Beetle
QLB can be rather difficult to treat because the most damaging stage of the QLB, the larva, are protected by living within the trees themselves. Some people try treatment with a systemic pesticide with the active ingredient imidacloprid, but this method has not yet been validated through research. If you choose this method, read the label first and follow all directions and restrictions. Systemic pesticides have strict limitations on the type of plants with which they can be used, especially fruit-bearing trees. This method can be hit or miss. In order for systemic pesticides to work, the beetle needs to feed on the vascular system of the plant, but the beetle can easily live deep within the tree and not touch the vascular system at the time of application.
Researcher Roxana Myers from USDA-PBARC has been studying insect-parasitic nematodes (Heterorhabditis indica strain HM264) as a control for QLB. These nematodes have been collected from soil on the Big Island and can prey on QLB larva. This research is still relatively new and is ongoing, but has shown promise as a non-chemical control for QLB. The nematodes are injected into the tunnels made by QLB and they hunt within the tree to find the larva. If you are interested in using these seek-and-destroy nematodes or have any questions, email biisc@hawaii.edu. Please note that these nematodes can take approximately 2 weeks to rear and we want to provide the freshest nematodes to be used in treating QLB, so reach out in advance to give us a chance to prepare them for you.
Queensland Longhorn Beetle Nematode Treatment Webinar hosted by the Hawaii Ulu Cooperative
Update from Hawai‛i Dept of Agriculture, July 2020
Confirmed host plants:
- Kukui (Aleurites moluccanus)
- Breadfruit (Artocarpus altillis)
- Various citrus (Citrus spp.)
- Queen Sago (Cycas cirinalis)
- Cacao (Theobroma cacao)
- Mulberry (Morus sp.)
- Trumpet tree (Cercropia obtusifolia)
- Kalamungay (Moringa oleifera)
- Norfolk pine cut logs (Araucaria heterophylla)
- Avocado (Persea americana)
- Hibiscus (Hibiscus spp.)
- Croton (Codiaeum variegatum)
- Elder berry (Sambucus nigra)
- Gunpowder tree (Trema orientalis)
Unverified, but possible host plants:
- Loquat (Eriobotrya japonica)
- Tree spinach, Chaya (Cnidoscolus aconitifolius)
- Passion fruit (Passiflora edulis var. flavicarpa)
- Cycads spp. (Encephalartos Horridus, Encephalartos Laurentianus, Dioon Merolae, Microcycas)
- Jade plant (Crassula ovata)
- Starfruit
- Durian
- Alahe’e (Psydrax odorata)
- ‘Akia (Wikistroemia sandwicensis)
Are you sure it’s a Queensland Longhorn Beetle?
Not sure if it’s a QLB? Use this guide to see the most commonly found longhorn beetles on Hawai‛i island. You can always contact us to ID your beetle (make sure to include pictures!).
