Wednesday, July 9, 2014

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.

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.

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.

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.

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.

Friday, June 27, 2014

Perception, Reality, and Doing the Right Thing

  • Post written by Dan Hilburn

Why is it so easy to get funding to extinguish fires and so hard to get support for eradicating weeds? That question was asked by one of the speakers at last week’s Oregon Invasive Species Council meeting. It is true -- we’ll spend millions of dollars putting out a wildfire even where they are a natural part of the ecology. The Two Bulls fire near Bend burned through $5 million as well as 7,000 acres. That works out to $714/acre!

On the other hand, we spend barely $0.02/acre on noxious weed EDRR (Early Detection Rapid Response) in Oregon. This is true even though damage from noxious weed invasions can be more serious ecologically than fire damage.
Fighting the Two Bulls fire near Bend Oregon cost $714 per acre.
With invasive species, nothing bad happens quickly;
the threat can be more ecologically damaging, but it is insidious.

We spend barely 2 ¢ an acre protecting Oregon's ecosystems from invasive weeds.


Native plants grow back after fire, but they don’t compete well with invasive weeds. Weed invasions can be described as ecological wildfires in slow motion. That’s the problem – the slow motion part. Fires are immediate and frightening; weeds are slow and insidious. People perceive one as a threat right now and the other as a lower priority. If you ignore noxious weeds, nothing bad happens – for a quite a while, often years.
The Metolius River is being invaded by non-native ribbon grass
The Metolius River is being invaded by non-native ribbon grass.

There was a field trip at the same meeting to see the ribbon grass infestation on the banks of the Metolius River.
USFS Public Notice of herbicide treatments
USFS Public Notice of Herbicide treatment

The USFS has been working on the NEPA documents to address weeds in the Deschutes National Forest including ribbon grass for a decade. Last fall the pieces fell into place and some herbicide trials were put out using a weed wiper and several different rates of Glyphosate and Imazapyr. The wiper was required because of a perception that the herbicides could most safely applied to the invasive ribbon grass and yellow flag iris by wiping it on the leaves. The reality proved to be a little different.

The weed wiper looks like a paint roller on the end of a hockey stick-shaped piece of PVC pipe. In order to work, the wiper has to be saturated with concentrated herbicide. That concentrate drips from the wiper as you work and it is impossible to push down sufficiently with wiper on ribbon grass growing out into the water without immersing the fuzzy part of the wiper. Several of the trial sites had good control on the bank with a halo of surviving ribbon grass in the water. A backpack sprayer would be more effective and if used carefully, e.g. spraying from the water toward the bank, at least as safe.
There's a perception that a backpack sprayer is safer than the wiper.
The reality is different.


 Mike Crumine demonstrating the wiper on ribbon grass
Mike Crumrine, the ODA noxious weed control
expert demonstrated the wiper method on ribbon grass. 

Mike Crumrine, the ODA noxious weed control expert that put in the plots, calculated that the wiper trials used 19.5 oz of Glyphosate and 9.4 oz of Imazapyr. You could do the same work much faster with a backpack sprayer and only use 8.2 oz of Gyphosate and 4.1 oz. of Imazapyr.
The difference comes from using a dilute solution with the backpack sprayer vs. a concentrate in the wiper. Water monitoring during last fall’s trials showed no detectable levels of either chemical in the river. I’d expect the same result with a carefully applied backpack treatment.

I’m not so naïve to think we can eradicate invasive weeds on the banks of the Metolius without getting minute quantities of herbicide into the water, but we don’t have a viable alternative. Weed pulling and solarization with plastic have already been tried and discarded as impractical and worse for the river and the native vegetation. Pulling ribbon grass “brings up the whole bottom,” and solarization kills everything under the plastic. If you stand on the Camp Sherman bridge and look downriver, you can see a little island that was covered with plastic to smother the ribbon grass. The little willow that used to grow there died during the solarization. Luckily we have non-persistent formulations of herbicides that are labeled for aquatic use.

So the perception is that wildfires are worse than weeds and that wipers are safer than backpack sprayers. My point is that the reality is sometimes different. We need to fund our weed EDRR programs like we fund fire suppression and we need to use the best available tools when we attempt to eradicate invasive species from high value habitats.

Monday, May 12, 2014

Proposed Commerce - Dan's Thoughts and Comments

-- Posted on behalf of Dan Hilburn

ODA is often asked to comment on permit applications and proposed import/export ideas. Typically I farm the requests out to staff members for analysis. When their reports come back, I combine their research on the risk with my reading of Oregon’s regulations, and submit comments. Occasionally the risk level is obvious and the laws clear; more often that not, there are grey areas.

This week we were asked to comment on four issues:
  1. Importation of onion leaves for consumption from Hawaii
  2. Commercial sales of a giant African millipede as a pet
  3. Importation of raspberries and blackberries for consumption from Ecuador
  4. Ash logs from the emerald ash borer-infested areas in the central US transiting Oregon for export to Asia. 
 My thoughts and comments follow; the thoughts are in italics.

1.) Onion leaves. 

Dan thinks, "We’re importing onion leaves? You’ve got to be kidding. Oregon grows tons of onions and we throw the tops away. I see that USDA has done a 39-page pathway risk assessment and concluded that only three potential pests have a medium or high likelihood of introduction via this pathway! Of course, none of the three are covered by Oregon quarantines because who would have imagined anyone would want to import onion leaves?"
Onion leaves
Oregon grows many tons of onions and discards the tops.
Oregon may import onion leaves from Hawaii. 

None yet. There are no Oregon laws that apply. The pathway risk assessment is thorough and USDA will use it to choose appropriate phytosanitary measures to mitigate the pest risk. We’ll comment on the final proposal if we think they’ve missed something.

2.) African millipede pet. 

Dan thinks, "Another giant African millipede? What’s wrong with the five species we’ve already determined to be low risk put on our approved list? According to staff the scientific name given is wrong, though widely used in the pet trade. There is very little known about this species except that it comes from central Africa and it eats lettuce and cucumbers in captivity. Oh, it is also readily available on the Internet."

“Oregon Department of Agriculture staff have reviewed this application and draft permit. The scientific name should be Spiropoeus fischeri [instead of Mardonius parilis]. We have no concerns. [Except the general unease that comes from knowing someone, somewhere will release them and we are just guessing as to the risk. Note to self: add this species to the approved list. Cross fingers.]

3.) Berries from Ecuador. 

Dan thinks, "I know there is demand for fresh fruit year-round. I like fresh berries on my cereal and now that they are available all year at our grocery store, I’ve gotten spoiled. We’re already importing lots of fresh fruit from Chile during our winter (their summer). 

None yet, I haven’t heard back from staff. [The fact that Oregon grows blackberries and raspberries increases the risk. On the other hand, off-season introductions of fresh fruit that are eaten soon after importation are relatively low risk.]

4.) Ash logs to Asia. 

Dan thinks, "It can’t be economical to ship ash logs half way around the world! Actually it probably is because of all the empty containers and light ships heading back to Asia. The pest risk for the receiving countries is low because emerald ash borer likely came from Eurasia. Of course we don’t have regulations because we’re preempted by the federal emerald ash borer quarantine and no one has ever proposed such an improbable scheme. The staff analysis indicates the risk is high. I’ll have to bluff."
Oregon may ship ash logs infected with emerald ash borer. 
So far, the pest is not found in the state. 

“Thanks for asking for our thoughts on this proposal. We do have concerns. Here is our feedback:

1.) Oregon doesn’t have state regulations that would apply. On the other hand, Oregon does have native ash trees and ash is an important street tree. Keeping EAB out of the state is a priority.

2.) The risk from the proposed actions as described would be acceptable only during the months of December through February. During the winter we’d expect the logs to arrive cold and the weather would be cool enough here to make EAB emergence unlikely. If the shipments were restricted to the winter months, we’d be comfortable with the proposed protocol.

3.) For non-winter shipments, we’d like to see additional safeguards. Here are some possibilities that would give us more comfort:
  • Shipping in refrigerated containers.
  • Fumigation at origin.
  • Debarking before inspection, and inspections of individual logs rather than piles of logs.
  • Restricting origin of logs to outside the EAB-quarantined area, and setting a maximum time logs could be in transit through Oregon.
Thank you for consulting us. Please keep us informed of any new developments.”

In this business, we keep our fingers crossed a lot -- and put out lots of insect traps to detect what gets missed at the borders. Living in a global economy makes for grey areas, and grey hairs. I always ask my barber to cut the grey ones, but she misses more and more!