Some Christmas trees coming into Hawaii from the Pacific Northwest aren't coming alone.

Trees in four containers from Oregon were infested with slugs and denied entry to the state, said Leslie Iseke, plant import specialist in the state Department of Agriculture Plant Quarantine Division.

The slugs were sent to snail/slug specialist Robert Cowie at the University of Hawaii's Center for Conservation Research and Training for identification, and he said they are “;potentially quite serious pests.”;

“;These particular slugs ... are two of the more important agricultural pests in Europe, North America and New Zealand where they were introduced,”; he said.

“;People say temperate-climate pests, like yellow-jacket wasps for instance, won't survive here,”; Cowie said. “;But when they get here and survive, they escape and go to the mountains, where it's cooler.”;

The same happens with slugs, he said, noting a graduate student working on the Big Island found alien species at higher elevations that are from temperate, not tropical, parts of the world.

The slugs found on the Christmas trees “;will certainly become a pest if they're established here in the vegetable-growing area of Kula, Maui, and places like that,”; Cowie said. “;They've already got some temperate species.”;

Iseke said plant quarantine inspectors have so far looked at 130 or so containers and have 70 more to go. A container could contain hundreds of trees, she said.

Each container is opened for a visual inspection, and if pests are found, trees are pulled for a better look, Iseke said. “;Sometimes we pull them out to spot-check, even if we don't find anything.”;

Trees are shaken and pounded on the ground “;so hopefully whatever organisms are on the tree are shaken out on white maps,”; she said.

Some slugs are so tiny it is hard to see them just by spreading the branches open, so “;the best thing is shaking,”; she said.

If a heavy infestation of slugs is discovered, the container is held at the port until the pests are identified, Iseke said. “;It lowers the risk if they're already present in Hawaii. If the species is not known to occur here, then we take action.”;

Containers with infested trees are not allowed into the state, she said.

The numbers of pests found on the trees have decreased in recent years because trees are required to be shaken mechanically at the origin before they are loaded, Iseke said. “;The containers are cleaner than when I started (in 1990).”;