Research updates for the geographical distribution and chemical control of the hala scale, Thysanococcus pandani Stickney, throughout the Hawaiian Islands

The hala scale, Thysanococcus pandani, was first detected in Hana, Maui in 1995. The primary host plant for T. pandani is the hala tree, Pandanus tectorius, which is found in coastal areas of the Hawaiian Islands and frequently planted as a landscape tree. P. tectorius trees are native to Hawaii and culturally significant, as some species were part of the original canoe plants brought by Polynesian voyagers across the Pacific. Since its initial introduction in Maui, it is now widespread on Maui and Molokai, and is established on limited locations on Oahu. In April and May 2021, a statewide survey was conducted to evaluate its current distribution with an emphasis on Kauai, Hawaii Island, and Lanai. The Lanai population that was previously detected has been eradicated. There was no hala scale detected on Kauai and Hawaii Island at the available survey sites. Chemical control methods were also evaluated to determine if any treatments could be effective for reducing or eliminating hala scale in landscape settings. An open-field potted plant experiment was conducted testing the efficacy of various foliar insecticides on T. pandani infested plants. Our results so far indicate that flupyradifurone and buprofezin reduced the overall infestation levels and improved the visual appearance of the infested plants. This research provides potential control methods against hala scale, and the latest distribution of the pest statewide.