Charles Nelson and Dr. Hara doing an equipment check before flipping the switch to another chamber full of Christmas trees.
Strange but true: Christmas trees love the heat. Hot water, that is. Retailers suggest filling the tree stand with hot tap water, which the stem can absorb more readily than cold. But fresh, green, rehydrated trees are just a fortunate side effect of the plant disinfestation spray chambers invented by Arnold Hara of the Department of Plant and Environmental Protection Sciences and Charles Nelson of Molecular Biosciences and Bioengineering, along with UH-Hilo’s Marcel Tsang. Their main goal at present is to keep the Islands safe for Christmas.
It all started with cold water—drenching floods in the Pacific Northeast, where the majority of Christmas trees imported to Hawai‘i are grown. The ground became so soaked that banana slugs slithered into the trees to escape from drowning, and when the trees were cut down and shipped over, they came along for the ride.
Glistening and bright yellow, the slugs may look like a new type of Christmas ornament, but there’s no holiday welcome for these invasive pests, which may carry rat lungworm disease. Banana slugs aren’t yet found here, and the Hawai‘i Department of Agriculture’s Plant Quarantine division and CTAHR intend to keep it that way.
This isn’t the first year they’ve been discovered in tree shipments, but they’re far more numerous than ever before, infesting at least half the containers. So Dr. Hara came over from the Big Island, bringing with him the disinfestation chamber usually employed to keep coqui frogs from leaving that island to supplement the one already used on O‘ahu. Constructed from ordinary shipping containers lined with pipes and spray nozzles, the chambers are deceptively simple— and extremely effective. Fifty to seventy trees are piled inside and bathed in 118°F water for a mere eight minutes. The water’s even recirculated and reused.
Slugs aren’t the only pests sheltering in the branches of the Christmas trees: A Western fence lizard, a salamander, wasps, and frogs have also been found in this year’s shipments. The state has no other feasible method of disinfesting the trees besides manually shaking each one, making the invention not only ingenious but critical to the biosecurity of the Islands. And knowing we’re being protected from invasive species is enough to give us all a merry Christmas.