Host preferences of non-native Acalolepta aesthetica (Coleoptera: Cerambycidae) on the Island of Hawai'i

1. Understanding the host preferences of non-native polyphagous insects is a key step in anticipating their impacts.

2. We apply a technique from wildlife ecology, a resource selection function, to quantify the host preferences of Acalolepta aesthetica  Olliff (Coleoptera: Cerambycidae: Lamiinae) in its non-native range on the Island of Hawaiʻi. We then visually surveyed its preferred host to map its distributional extent and conducted laboratory no-choice tests to assess risks to common native woody species.

3. The preferred host of A. aesthetica was the state tree, Aleurites moluccanus (L.) Willd., the kukui (or candlenut). Cacao (Theobroma cacao L.) was the second most preferred host. Infestations were also observed in Citrus species, Artocarpus altilis (Parkinson) Fosberg (ʻulu or breadfruit) and Persea americana Mill. (avocado), but preferences among these taxa were statistically indistinguishable.

4. Acalolepta aesthetica females oviposited on all tested species in no-choice trials, but larvae growing within ʻōhiʻa (Metrosideros polymorpha Gaudich.) and koa (Acacia koa A. Gray) died. It therefore poses a low risk to these two tree species, which are foundational to Hawaiian native forests. Acalolepta aesthetica was able to complete its development within ʻōlapa (Cheirodendron trigynum (Gaudich.) A. Heller), which could be monitored if the distribution of A. aesthetica spreads to native forests. 

5. The host species preferred by A. aesthetica are highly valued for agricultural, horticultural and cultural uses. Developing monitoring and management techniques for this cerambycid and employing strong biosecurity could prevent human-mediated spread and limit negative impacts to other Hawaiian Islands, the U.S. mainland, and the world.