With more hala trees in Waikiki becoming infested with the hala scale, KHON-2 TV and Hawaiʻi Public Radio consulted the expertise of Zhiqiang Cheng and his PhD student, Mason Russo, of the Dept. of Plant and Environmental Protection Sciences.
Halas are important landscape trees in Hawaiʻi, and leaves of the tree are integral to Hawaiian weaving and cultural practices. The invasive hala scale insect isnegatively impactingnative hala forest ecosystems and landscape hala trees throughout the state; widespread infestations have already caused significant damage on Maui and Molokaʻi.
In discussingthe pest and ways to manage infestations, Cheng covered various projects he has worked on since 2016, includingchemical controls, and biological control as a likely management tactic.
“This insect causes negative economic, cultural, and ecological effects throughout impacted islands,” says Cheng.“But in places like Singapore, Thailand, Indonesia, Malaysia, essentially Southeast Asia, hala scale is not a major pest, most likely because there are natural enemies and biocontrol agents to keep them in check.So the idea is to hopefully make use of those controls here.”
Cheng’s Lab is looking into treating plants with low-risk chemicals that will kill the insects, but keep the tree alive. “They’re on the horizon and we know they work very well, so the goal is to get them licensed, get them labeled for hala scale so people can actually use them,” Cheng says.
Mason’s research also focuses on whether hala forests can regrow after being infested by the hala scale. Although the literature suggests there will be no regrowth, that forests will be gone forever, Russo hopes the literature is wrong and halaforests can regrow to some extent. But if it is true, the priority for biological control may be even greater.
“We will compare the current status of forests on islands with hala scale, such as Molokaʻi and Maui, with islands without infestation, such as Hawaiʻi Island and Kauaʻi. And we're going to evaluate all the life stages of the forest,” says Russo.
“Public advocacy regarding invasive insect species,” Cheng adds, “is an excellent way to share information about target pests. This can increase general interest and help lead to the detection of new infestations.”
Watch the KHON-2 coverage and HPR coverage.