Hawaii’s Department of Land and Natural Resources has been closely monitoring the outbreak since it was detected in January. 

According to an update Monday on DLNR’s Facebook page, officials believe that the the defoliation by the native moths follows a natural cycle. 

Outbreaks of this native insect are a natural phenomenon, as indicated by oral accounts by Hawaiians describing similar outbreaks before the first documented outbreak in 1892. Researchers believe these disturbances likely play an important ecological role by eliminating unhealthy trees, thinning dense young koa stands, and providing an influx of nutrients into the forest ecosystem. 

However, little is known about the causes and full natural cycle of this phenomenon. Additionally, an invasive psyllid insect that was first detected in Hawai‘i in 1966 – and was not present during previous outbreaks – could damage new shoots of recovering trees. 

DLNR says there are no methods for slowing or preventing the moth outbreak. 

Aerial spraying of insecticides would harm other forest organisms and is not feasible on a large scale. Biological control is not possible with a native species because its natural enemies are already present in Hawai‘i, and there is no outside source for predators or parasites that would be specific to the moth.

In addition to monitoring the spread of the outbreak, DLNR is seeking funds to investigate natural controls of the moths using traps or baits, and monitor recovery of the forests and the response of invasive plant populations. This information will be useful for managing future outbreaks if they are determined to harm the forest.

(Photos: DLNR)

— Sophie Cocke