Alder root rot, Paterson's curse, imported fire ant, and now an aquatic plant commonly called rock snot. The unattractive names match the insidious nature of the organisms on Oregon's annual list of the 100 most dangerous species threatening to invade the state.

Department of Conservation photo

A scientist holds up an example of rock snot.

"These are species that have established and are harmful in other places with environments similar to Oregon's," said Dan Hilburn, administrator of the Oregon Department of Agriculture's Plant Division, and member of the Invasive Species Council. "These are species not yet established in Oregon and we want to keep them out. We want to focus on exclusion, early detection, and eradication of those things that can be eradicated. The species on this list of 100 can still be eradicated if found in Oregon."

The Invasive Species Council coordinates public and private activities on unwanted, non-native species, and has issued its list of the 100 most dangerous invaders for the past four years. With limited resources available to battle such species, the council wants to create an awareness of high priority organisms to exclude from Oregon. The list includes mammals, birds, insects, weeds, microorganisms, and more.

It's too late to get rid of Himalayan blackberry, Scotch broom, or many other non-native species that have flourished in Oregon, according to Hilburn.

"We are looking to prevent the next Himalayan blackberry or Scotch broom," said Hilburn. "When it comes to battling invasive species, the best bang for the buck is keeping them out."

It would not be hard to create a longer list of species that threaten Oregon, but the council wants to zero in on the 100 worst. The list does not rank the species, as they are all high priority.

Getting off the list is more difficult than getting on. New threats emerge each year, but only a few are worthy of bumping listed species, according to Hilburn. This year, three such invasive species have cracked the top 100.

One of the new species is rock snot. It has the scientific name of Didymosphenia geminate.

One look at its yellowish-brown slimy appearance explains the origin of the name. The microscopic, single-celled aquatic plant thrives in cold water. When millions of these tiny organisms collect, they form impenetrable mats that can cover miles of stream bottom, choking out native plants and animals, and disrupting the food chain. That threatens the biodiversity so important to creeks, streams, and headwaters of rivers. The organism has yet to be detected in Oregon, but has been found in all its neighboring states. It is of particular concern right now to New Zealand.

"The jury is still out on this organism," says Mark Sytsma, director of Portland State University's Center for Lakes and Reservoirs and council member. "No one knows where the new, aggressive form of this algae came from. We do know it can dramatically alter habitat quality in a stream. The thought is it spreads on fishing gear, particularly felt-soled waders. We have seen the same thing with the spread of New Zealand mud snails and whirling disease. It reinforces the importance of making sure gear is cleaned and dried after each use."

Another species added to the list is Amur goby (Rhinogobius brunneus), a small predatory fish recently detected in neighboring Washington. The invasive fish is especially threatening to salmon eggs.

The third added species is Xylosandrus crassiusculus, better known as the granulate ambrosia beetle. The tiny wood-boring beetle is established in the southeast United States, but was discovered in The Dalles in 2004, leading to ODA spray projects last year and this year that appear to be keeping the pest from establishing in Oregon. The beetle attacks more than 200 species of trees and shrubs– many of which are common in Oregon.

Three species have come off the list of 100 most dangerous invaders to Oregon. Japanese oyster drill, an aquatic invertebrate, has already established in a couple of Oregon estuaries but seems to be a minor pest that can be controlled. Two insect species, blueberry maggot and glassy-winged sharpshooter, remain potentially serious pests of agricultural commodities but don't appear to be a threat to Oregon's natural environment. Both have been removed from the list.

The Invasive Species Council uses the list of 100 worst invasive species as a public education tool.

"It's important for the public to realize there are a lot of species, if established, that would be harmful to Oregon," said Hilburn. "Oregonians need to keep their eyes open for things that are new and different, and report them when they see them. That way, the proper experts can identify the species and deal with it."

The special invasive species hotline (1-866-INVADER) receives several dozen phone calls a month from Oregonians who see something they don't think belongs. The reports are farmed out to the appropriate agency for follow up.