Wednesday, November 30, 2011

Christmas Tree Hitchhikers

Oregon’s frantic Christmas tree harvest is winding down. In just a couple of weeks, seven and half million trees are cut and shipped to retail yards around the world. Only 8 percent of those harvested remain in Oregon. This is a busy time for Oregon Department of Agriculture (ODA) inspectors and their counterparts in receiving states and countries. All of them are doing their best to ensure that pests and diseases are not hitchhiking on the trees.

Before coming to Oregon, I was an inspector in Bermuda, and I often looked at Christmas trees on the docks in the sunny, warm Hamilton harbor. Truck drivers there traditionally take a small branch from the first Christmas tree shipment and insert it in their truck’s grill. Bermudians smile when they see that little reminder of the approaching holidays (Christmas & Boxing Day).

Every one knows Christmas trees vary a lot in shape and desirability from a consumer’s point of view. None of that matters to inspectors. They focus on insects, slugs, tree frogs, Swiss needle cast, and other potential hitchhiking invasive species. From my days in Bermuda, I remember trees from Canada being the cleanest and trees from the Southeast United States being the buggiest. Whether or not there had been a hard frost prior to harvest made a big difference. Oregon trees were always lush and green, but if they hadn’t been exposed to a frost, they were carrying hitchhikers. We’d thump the trunks on the pavement and look for potential pests among the critters that dropped out.

Bermuda, like many islands, has been severely impacted by harmful invaders, including a scale insect that nearly wiped out the endemic Bermuda cedar. They have good reason to be careful with imported plant material.

So far, 2011 has been a good year for Oregon Christmas tree exports. A total of 99 percent of the trees that were certified for export also passed their import inspection at the other end. The few that didn’t included five truckloads rejected at the Mexican border (yellowjackets, weevils), one container turned back in Japan (strawberry root weevil), three fumigated in Guam (spiders), six held in Hawaii (slugs), and one held in Columbia (unidentified bug). Yellowjackets, slugs, and weevils are all known invaders; hats off to the sharp-eyed inspectors that found them.

Inspections are important in the fight against invasive species, but they are not a panacea. As with other commodities, only a small percentage of Christmas trees are checked on either end. The reason is simple; there are a lot of trees and only a few inspectors. Oregon has 10 inspectors working full time on Christmas trees in the fall. That seems like a lot, but if we estimate that 6,900,000 trees are exported (92 percent of total harvest) and the entire harvest happens over 20 working days, each inspector would have to look at 1.2 trees per second to inspect every tree! The best they can do is look at a sample and catch the obvious problems.

What the world really needs is a way to “pasteurize” Christmas trees. Traditionally, trees were shipped straight from the field “as is”. Many growers now use mechanical shakers to remove dead needles and surface hitchhikers. That helps, and some markets now require shaking. Unfortunately, no one has developed a standard, thus the efficacy varies depending on the speed and duration of the shaking. Starting this year, Mexico required 15 seconds of shaking at 700 rpm as well as an insecticide spray prior to harvest. That seems like overkill. Spinning, bouncing, and blowing have also been tried, but no one has tested the efficacy of these methods.

This year ODA started testing different shaking and spray regimes. It is a first step toward developing standard best management practices that will reliably remove potential pests from these famous holiday icons.

In my dreams, we would offer substantial monetary prize for the first person to develop a fast and economical way to “pasteurize” Christmas trees. We could name the process after the developer, ______(your name here)-ize, so Louis Pasteur could quit turning in his grave, and we could eliminate Christmas trees as a pathway for introduction of invasive species. Wouldn’t that be nice?

None of this matters to Oregonians if they cut or choose locally grown trees. We’re lucky to live where Christmas trees are beautiful, inexpensive, and abundant. For us, the best practice is to thump the trunk in the driveway a couple of times before bringing the tree inside. Your kids might enjoy looking for native bugs among the dead needles, and you won’t bring these annoying Christmas guests inside! 

Dan Hilburn

Tuesday, November 15, 2011

Pass the Fruit Salad, Please

Spotted wing drosophila on ripe fruit. Photo courtesy of
A year ago I wrote about spotted winged Drosophila (SWD) in Oregon and the lessons learned from the first year of survey, management, and personal consumptive fruit sampling. Since then, another season has passed. We’ve got another year of experience and another belly-full of Oregon fruit under our belt, and we’re gaining confidence that SWD is not the nightmare we once feared.

In a nutshell, here is what we’ve learned from the perspective of growers, researchers, regulators, and consumers:


-Growers, including organic growers, can manage this pest if they pay attention and are ready to act when their crop starts ripening.

-SWD attacks ripe, soft fruit (especially raspberries, blackberries, and blueberries). It doesn’t bother green fruit or hard fruit like apples or pears.

-Populations are low in the spring and early summer. SWD builds up in late summer and fall. Numbers in the Columbia Gorge are consistently much lower than western Oregon.

-Grapes are not a preferred host. SWD is present in vineyards in the fall, but it seems to be attracted to split or damaged grapes.


-There is a lot of research going on, and we understand this pest much better now than when it first showed up (, but there are still unanswered questions:

-Trap counts have increased dramatically in the fall the last two years. Thankfully, this is after our fruit crops are harvested, but we don’t understand why this happens. There were high trap counts all last winter, and then the population crashed in March. That’s weird. It would be nice to know what is going on.

-The standard trap (plastic cup with drilled holes) and lure (apple cider vinegar) is not very sensitive and it catches a lot of other non-pest Drosophila. It works for research, but it isn’t easy for growers/homeowners to use. We need a better trap.

-SWD is not hard to control, there are a number of materials that work, including organics, but with multiple generations, resistance could build up quickly. We need robust management strategies that don’t rely so heavily on cover sprays.


-State and federal regulators across the country have decided not to enact quarantines for this pest recognizing they would have been impossible to enforce and consequently would have had a very low chance of success. Our decision in 2009 not to quarantine infested counties in Oregon was the right one.

-The Oregon Department of Agriculture (ODA) has worked with Oregon State University (OSU) and commercial crop consultants to make growers aware of this new challenge and management techniques they can use. The partnership has worked well.


-There is plenty of fresh local fruit available. It is a good idea to rinse it before you eat it; it could have been sprayed, and reducing your exposure to pesticides makes sense.

-If you buy or pick fruit and some goes soft, pick out the bad ones and throw them away.

-Finally, if you’re into unsprayed fruit, accept that you could get some extra protein now and then in the form of SWD eggs/larvae. You won’t taste or feel them, and they aren’t harmful to ingest. 

I once asked another entomologist what he recommended for western cherry fruit fly (another pest with similar habits). He said, “Never eat half a cherry!” Our bodies are fine with the occasional swallowed insect, even if our mind says “gross.” In fact, insects are an important part of human diets in many parts of the world. Think about the choice of trace amounts of pesticide residues or a little extra protein. Which would you prefer to eat?  

Me? I choose fresh fruit from either conventional or organic sources and wash it, sort out any soft ones, and enjoy it. Works for me. During this season of thanksgiving, we should be thankful that we live in a fruit-producing state and have so much fresh produce available to us. Spotted wing Drosophila isn’t going to change that. “Pass the fruit salad, please.”

Dan Hilburn

Sunday, November 6, 2011

Critters in Containers

Scientific name: Tremex columba and other species
(Hymenoptera: Siricidae)
Facts: Horntails are an unusal because their biology that is not typical of most Hymenoptera. The larvae feed in dead logs much like wood-boring beetle larvae. The adults resemble wasps but they have a wide waist and therefore a cylindrical body. Adults are often found ovipositing on logs. 

Photo credit: Bastiaan (Bart) Drees, Extension Entomology, Texas A&M University
A toad hitchhiked from China to Oregon in a container of granite in 2008. Three dozen wood wasps did the same thing recently in a container of machine parts.The first incident was followed by a nightmare of regulatory fumbling; the second was handled like a dream.

The Asian toad incident started when a sharp-eyed inspector in Portland opened a container and saw a “frog” hop out and then back in. The container was resealed. Federal and state agencies debated what to do and who should do it for nearly four weeks. The container was eventually fumigated, and when it was reopened, the “frog” (actually a toad) had croaked. Lots of people, including myself, were embarrassed at the clumsy official response. A multi-agency postmortem was held to figure out what went wrong. The incident report includes a three-page summary of a uncoordinated regulatory process involving a dozen different agencies and companies. A comedian could have turned it into a funny (but very embarrassing) comedy routine. Fortunately, the agencies involved took it seriously and learned from the experience.

The wood wasp incident of 2011 was handled much better. This time it was staff at the receiving warehouse that heard a rustling sound and noticed large insects in a container they had just opened. Recognizing there could be a problem, they closed the container door and notified the broker, who notified Customs.Customs called the USDepartment of Agriculture (USDA). It was Friday afternoon, of course, but USDA sent someone to the warehouse right away. The USDA inspectors found live wood wasps emerging from the wood packing material, resealed the container, and recommended a fumigation treatment. The Oregon Department of Agriculture identified the wasp as an exotic Tremex sp. (wood boring larvae, no native species in Oregon). Both agencies were there when the container was reopened to ensure that the fumigation had killed all the insects, including any larvae still hidden in the wood. The incident ended when the wood was incinerated, and the machine parts resumed their transport – this time without insect cargo.

The difference between the two incidents boils down to better communication and cooperation. No one took charge in the Asian toad incident. One agency after another passed the buck and said they didn’t have authority to do anything, or it wasn’t their problem. I was one of the people that fumbled.

When the 2011 wood wasp incident occurred, USDA took charge and called in ODA for support. Together we identified the problem, determined the level of risk, figured out what needed to be done, and saw it through. Nice job, team.Your quick action saved our trees from exposure to a new pest. Communication and cooperation were the keys to success.

The real heroes, though, were the staff that work for ESCO Corporation and their broker. A big THANK YOU to the folks that noticed a potential problem and reported it: Cedar Whitemen, Mike Plamondon, Shannon Parton, Tracy Ann Whalen, and Robert Boswell. This container had already cleared Customs, and they could have ignored the bugs and sent it on its way. Thankfully, they didn’t. For their good work, they are going to be nominated for an Oregon Invasive Species Council (OISC) award. I hope they win; they deserve recognition.

This is a perfect example of how everyone, not just government inspectors, needs to play a role in the battle against invasive species. Recognizing a potential problem and reporting it to authorities is often the first and most important step. Kudos to the ESCO crew for doing it right.

Individually, we don’t stand a chance at excluding invasive species, but working together, Oregon has a pretty good team! Thanks for being a player. And remember, we’ve made reporting easy with our toll-free invasive species hotline: 1-866-INVADER or Keep your eyes open—the next odd-ball invader could end up in your court!

Dan Hilburn