Say Goodbye to Our Black Walnut Trees

Photo from Google Street View

• Post by Dan Hilburn

Next time you drive out Center Street in Salem take a look at the black walnut trees on the State Hospital campus. Those big, beautiful trees are doomed. If you look up, you can see the tops are dying. Within a decade, they’ll all be dead and gone. The same fate awaits other black walnuts in Oregon. The killer is a fungus that causes thousand cankers disease (Geosmithia morbida) and it’s vector, a tiny insect called walnut twig beetle (Pityophthorus juglandis). This is an invasive species story with a twist – both the fungus and the beetle are believed to be native to North America, though not to Oregon.

Until recently walnut twig beetle was known only from the Southwest where it lived in harmony and obscurity with its host, Arizona walnut.

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Until recently, the walnut twig beetle lived in obscurity with its host, the Arizona walnut. 

The beetle expanded its diet to include non-native walnuts.
The killer fungus came along too.
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Unexplained die-offs of black walnuts in the mid-West in the early 2000’s were initially blamed on drought and/or the walnut twig beetle. Eventually researchers noticed large numbers of dark cankers under the bark of dead trees. And that led to the 2008 discovery of the associated fungus. The researchers named the fungus thousand cankers disease.

The walnut twig beetle, a type of bark beetle native to the southwestern United States and parts of Mexico, is the only confirmed vector of the pathogen. Apparently, it adjusted to non-native black walnut street trees and expanded its range throughout the West. The fungus hitchhiked with the beetle.

No one has yet figured out a control or management strategy that works. Severe pruning and burning of infested branches may slow the disease, but eventually, even big, healthy black walnuts succumb. Neighborhoods with black walnut street trees are going to look bare when they are removed.

It is sad that we’re going to lose some street trees in Oregon, but the real tragedy will be in the East where black walnut is native and treasured for it’s high-value wood. Several states have enacted quarantines to lessen the risk of human-aided introduction. The biggest threat is movement of infested logs and firewood.

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The biggest threat is people moving infested logs and firewood.

If the logs or firewood are put on a truck and moved to a mill, buyer or campsite, the beetles can emerge in a new place and Thousand Cankers Disease jumps ahead like a spot fire started by a spark.
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When trees die, people naturally want to sell the trunks and cut up the rest for their fireplaces. If the logs or firewood are put on a truck and moved to a mill or a buyer somewhere down the road, the beetles can emerge in a new place and thousand cankers disease jumps ahead like a spot fire started by a spark. Since it takes several years from infection to the first symptoms, by the time trees start dying no one will remember the shipment of infested wood that inoculated the neighborhood.

For us in the West, its a story of a native beetle/fungus with an expanded range attacking non-native street trees. The take home lesson is that firewood should be bought and burned locally. Don’t take it with you when you go camping out-of-state. The same principle applies to logs. When mills and kilns are local, pests and diseases are less likely to hitchhike to new areas.

I used to have a black walnut overhanging my driveway. The falling nuts were hard on my car and messy to clean up so I wasn’t sorry when the power company cut it down. Black walnuts are the sort of tree you enjoy if it is across the street and belongs to someone else, like the State Hospital -- I’ll still be sad to see them go.

1% for Protecting Oregon from Invasion

• posted by Carolyn Devine on behalf of Dan Hilburn 

“What if we decided we to spend 1% of existing fees related to trade and travel on invasive species?” That is the question Mark Systma, OISC Chair, and I posed to the Governor’s Natural Resources Cabinet last week.

Oregonians have another opportunity to do something bold in the field of environmental protection. The 1% pathways connection would be as audacious as the bottle bill and just as important in the long run. Here is a summary of the pitch we made to the Cabinet.

Improving Greater Sage-Grouse Populations Requires Managing Invasive Weeds

Invasive species are tied into most of the environmental hot topics of the day: clean water, working landscapes, reducing exposure to toxics, and protecting habitat for wildlife. For example, there is an ongoing effort to halt declines in Greater Sage-Grouse populations with the objective of keeping Greater Sage-Grouse off the endangered species list. Weeds such as cheatgrass and medusahead rye are part of the problem. When these invasive grasses move into Greater Sage-Grouse habitat, fires become more frequent than would naturally happen. This is bad for sagebrush and other native vegetation that the Greater Sage-Grouse depend on.

We won't have success protecting Greater Sage-Grouse without dealing with the related invasive species problem.

Fighting Weeds with Herbicides is a Necessary Evil

Another current topic we highlighted was herbicide drift from conifer release sprays. At first glance these appear to be a straight-forward cases of pesticide misuse, but guess which plants are out-competing the desired forest seedlings: mostly Scotch broom, Himalayan blackberry and other invaders. If it weren’t for these invasive weeds we wouldn’t be using so many herbicides.

A Growing Funding Gap for Fighting Invasives as Globalization Increases 

Hopefully, having established for the Cabinet that invasive species matter, we went on to describe the widening funding gap that we face in Oregon. The rate of introduction of invasive species is correlated with trade and travel. Hitchhiking weed seeds and woodborers are a side effect of globalization. Increasing trade and travel means more and more introductions. At the same time funding for survey and eradication programs is declining. We’re falling behind.

Solution:  Link Invasive Species Funding to the Pathways of Invasion

The ideal solution would be to link the funding for invasive species programs to the trade and travel activities that bring these problems to us. This is the essence of the 1% for invasive species proposal.

To do this we wouldn’t need to invent new taxes. We already collect fuel taxes, lodging taxes, landing fees, docking fees, imported timber fees, aquatic invasive species permit fees, and lots of other fees related to trade and travel. All we would have to do is to decide as a state to spend 1% of the revenue collected from those existing fees, about $5 million annually, on invasive species response and we could close our funding gap not just for next year but for the long run.

Cabinet members listened and asked good questions. How would the money be used and who would control its distribution? What about federal lands and federal agencies, do they pay their fair share? Do all the pathways have associated fees? What about the constitutional dedication of fuel taxes to roads and rights-of-way? Our agency already spends millions on vegetation control, would that count for something? Would this be like the 1% for art program? The questions indicated to me that they were thinking seriously about the proposal. Afterwards, Richard Whitman, the Governor’s Natural Resource Policy Advisor, indicated he’d talk to the agency heads individually and get back to us.

Now we wait with our fingers crossed to see if the idea catches hold.

I’m optimistic by nature but not naive. I recognize that because we are not proposing a new tax or fee, this idea would represent 1% budget cuts for other programs. However, an ounce of prevention is worth a pound of cure. For weeds, we know that for every $1 spent in preventing a new species from invading, the state saves $34 in management later. That's significant. We’ve put the ball in the air and our shot hasn’t been blocked yet. We’ll know if this first shot goes in by whether we get permission to draft a bill for the next legislative session.

If that happens we have a chance to move Oregon into another landmark natural resources decision in 2015. Are you on our team and ready to play? We’re early in the first quarter and it’s a long game.