HILO, Hawaii Island — The image appeared on Facebook on Nov. 24. It showed a tiny orange ant wandering on the bark of a pine tree. Accompanying it was the terse message:

“Home Depot Christmas Trees have Fire Ants!”

Within five days, the message posted by a Hilo resident had been shared 159 times. Home Depot spokesman Matthew B. Harrigan said the problem came to the store’s attention on Nov. 25.

Little fire ants cluster around a line of gel bait. Buyers may want to set up a “quarantine zone” before bringing their Christmas trees inside. Courtesy Big Island Invasive Species Committee

Even though only one person had contacted the store about the ants, Harrigan said that “out of an abundance of caution,” the store had quarantined the entire lot and opened a new lot on the other side of the store with trees that previously hadn’t been unloaded from the trucks.

Just how many people took fire ants home with their trees is not known. But the incident illustrates a very real hazard: When people bring home trees and other vegetation from elsewhere, they may also be importing unwelcome visitors.

Harrigan said the store traced the fire ant nest to “a tree or some trees that were next to the lot — part of the landscaping.” He said the store had “hired a vendor to treat the area.”

If anyone found ants in a tree they’d gotten from the store, Home Depot would give them another tree for free upon presentation of a receipt.

“The customers do not need to return the tree; however, the store can arrange to pick up and dispose of it,” Harrigan said.

That still leaves a potential problem for customers. Little fire ants are so named for a reason: although tiny, each ant packs a fiery, wasp-like sting. Even if customers carried infested trees home without getting stung, they might not want to risk putting them into their cars again. But if a queen ant happens to be on board the tree — not likely, since the trees were probably not on the lot very long — the ants could spread on the customer’s property.

Frannie Kinslow Brewer 

Franny Kinslow Brewer, the communications director for the Big Island Invasive Species Committee, has been on the front line in the battle against the ants.

“You don’t want the tree in your house,” Brewer said. “That could be very uncomfortable. “You don’t want to take that tree anywhere and continue to spread the ants.”

But she added, “Just because something has fire ants doesn’t mean you have to set it on fire.”

Instead, she suggested, anyone who brought a tree home — or has brought home any other plant matter, from lumber to poinsettias — may wish to set up a temporary “quarantine zone.”

In a driveway, front yard or other open space, spray a 2-foot-wide, unbroken ring of an insecticide such as Talstar (or other product containing Bithrenfin) or Sevin as a barrier around the tree or other object. Keep the tree within that circle for a few days; spread peanut butter on some sticks and put them inside the barrier with the tree. If, after a couple of days, there are ants clinging to the peanut butter, then use a bait insecticide such as AMDRO, which Brewer recommended  as “accessible and inexpensive.” If a queen ant is present, the worker ants will carry the poison bait home to her, ending the colony.

A container of AMDRO Fire Ant Bait advertises for about $14 on several online sites; Talstar can run from about $27 to $35.

Customers will have to weigh that price against the potential cost of living with stinging ants. Unfortunately, said Brewer, “There are no organic products right now that have been approved for use on little fire ants and are known to be effective.”

Brewer cautioned, however, against wholesale use of Talstar as a fire ant preventative over large areas, because it kills not just ants, but all insects, including beneficial insects such as bees.

Little fire ants are fairly indiscriminate killers. They’re a threat to bird nestlings, animals — they can blind a pet if it’s stung in the eye — native insects and humans. Especially vulnerable are gardeners and farmworkers.

What’s in your Christmas tree? Alan McNarie/Civil Beat

The Big Island Invasive Species Committee’s website has an extensive section on little fire ants, including a page on various insecticides and their uses in fighting the ants. More information on the ants and the threats they pose can be found in Jason Amstrong’s recent Civil Beat column,  “Little Fire Ants are on the March in Hawaii.

Little fire ants weren’t the only unwanted Christmas guests that trees may be carrying.

“There are mites, there are wasps, there are flies, there are slugs, there are all kinds of things that could be on a Christmas tree, Brewer said.

Some of those pests may be picked up at local retail lots, as apparently happened at Home Depot. But others may be overseas travelers. A 2012 press release from the Hawaii Department of Agriculture, noted that its inspectors had held 74 out of 150 containers of Christmas trees from the Pacific Northwest because they were “widely infested with slugs and other pests that are not found in Hawaii.”

And those pests can sometimes carry other even smaller invaders: Slugs, for instance, can be carriers of rat lungworm disease.

“Once an invasive pest or disease becomes established in Hawaii, it may have a devastating impact on Hawaii agriculture by causing damage to crops and is often costly for the state and growers to control.  Invasive species may also harm Hawaii’s unique ecosystem,” noted the press release.

There were so many problems with Christmas trees that the HDOA began sending inspectors to Oregon to check trees before they were shipped. Still, Brewer noted that ag inspectors could check sample trees, but probably not every tree in a shipment.

One way to reduce the risk of some unwanted visitors, she said, was to get trees grown in Hawaii. The committee’s website has a page that lists local Christmas tree growers, and she says her organization is seeking more growers to add to that list.

And some island residents are avoiding the problem by avoiding cut trees altogether — buying trees in pots and keeping them for years, or using artificial trees, or just not having a tree.

“No tree for me!” noted one Big Island Facebook user, citing the fire ant concern. “I’ve hung ornaments from house plants in the past, then I started hanging them from hooks in the window frame so they’d catch the light. Some of those ornaments are still in the windows from previous years.”

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