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| Close-up view of the parasitic dodder (Cuscuta) vine-bearing an insect induced gall. |
Chinese Soybeans, Weed Seeds, and Probability
I have a two-part story to share. The
first part began here in Oregon about two weeks ago. The second part takes
place in the future—I created it to illustrate a point. The story starts with
the arrival of a shipment of organic soybeans from China at the Port of
Portland. The soybeans were destined for a processing plant in Rickreall where they
would have been turned into organic chicken feed. They didn’t get there.
Customs and Border Protection (CBP) inspectors
took samples at the dock and found two species of noxious weed seeds
contaminating the soybeans—dodder (Cuscuta
sp.) and Benghal dayflower (Commelina
benghalensis)—both are on the federal noxious weed list. CBP issued an
emergency action notice stopping the soybeans from entering the country.
The importers had a lot of money tied
up in the shipment and customers waiting; they pleaded for leniency or some
special process to allow the soybeans to enter the United States. Officials at the
US Department of Agriculture (USDA) and Oregon Department of Agriculture (ODA)
discussed options for a rescue treatment and other forms of mitigation. Fumigation
is sometimes an option in situations like this, but not with weed seeds—seeds
are not on the available herbicide labels, and there is no data indicating they
would effectively kill the seed without greatly reducing the organic nature of
the soybeans.
Sealing the containers and allowing
them to proceed to destination was considered. Making chicken feed out of
soybeans involves several steps including grinding and exposure to high heat. The
processed chicken feed itself would probably be low risk, so why not seal the
containers and let the soybeans proceed to the manufacturing plant? An
inspector could be present to make sure everything was processed accordingly. The
importer was willing to pay for the inspector’s time. Would you have allowed
that?
ODA said “No.” Our reason for not
allowing the contaminated soybeans into Oregon is illustrated by the following
fictional account of what could have happened. Numbers have been rounded for
ease of calculation.
Assume 20 containers each with 50,000
lbs of soybeans for a total of 1 million lbs. CBP took several samples of about
two gallons each and found 10 dodder and 10 Benghal dayflower seeds per sample.
Let’s estimate that two gallons of soybeans weighs 10 lbs so that we’re dealing
with 2 weed seeds per lb, one of each species.
Dodder seeds are hard and small, somewhere
between a speck of dust and a grain of sand in size. Benghal dayflower seeds
are also hard, but larger, about the size of a grain of rice. Thus our
fictional account begins with 2 million weed seeds mixed in to 500 tons of
soybeans on the dock in Portland. In this scenario, ODA says “Yes” to allowing
the shipment to enter the state and proceed to Rickreall. Being cautious, they
require the containers be sealed first so that the chance of weed seeds dribbling
out along the highway is minimized. The system works and all the soybeans and
the weed seeds arrive at their destination.
Next the containers are dumped into a
hopper in a covered breezeway. Everyone is careful and 99.99% of the weed seeds
make it directly into the hopper. In spite of the care taken, two hundred weed
seeds remain in the bottoms of the containers and on the unloading dock. A conscientious
inspector vacuums out the containers and verifies that everything went
according to plan. She sweeps the small quantity of soybeans from the edge of
the concrete slab into the hopper. She is good—in fact, she is 99% effective. Now
only two weed seeds remain, plus several more in the vacuum bag. Months later,
the vacuum bag becomes full and is thrown in the trash. On garbage day, it is
picked up and hauled to the landfill where it is buried. After a couple of decades,
all those seeds are dead.
Meanwhile there are still two viable
weed seeds in play. One of them is lodged in the hinge of a container; the
other was on the concrete slab surrounding the grain hopper before it stuck
briefly to a trailer tire and got moved to the processing plant driveway. It remains
for a month until it is washed into the ditch during a rain shower.
The other seed is lodged in the
container door hinge. It travels the world but remains stuck under some rust. Sometime
later the container is sandblasted and the seed dies. Now there is only one
seed left. After being washed downstream, it settles out where the water
collects when the ditch dries up. Weeds grow up in the ditch, and the dodder
seed germinates. It is a parasitic plant that latches on to other plants and
gets its nutrients from them. It looks like a stand of spaghetti. Nobody
notices it twined around its host. That year the dodder plant flowers and
produces 200 seeds. Some of them are washed further downstream the next winter.
Earthworms and other little critters eat some and poop them out where they
wander. After a few years, there is a small patch of dodder plus a couple of
satellite patches some distance away. The total dodder seed bank is now up to 10,000
seeds each capable of remaining viable for a decade or more.
A road maintenance employee sees the
weeds and sprays over the patch. Almost all (99%) of the dodder plants are killed.
But because of the seed bank, dodder returns next year and the year after that,
and each year there is more, and it spreads. Some years later, a farmer notices
the unfamiliar weed in his field and calls in an expert from Oregon State University.
They identify it immediately as Cuscuta
sp., and take a sample for further analysis. Everyone is baffled when it is
identified as a species from China never before seen in the United States. ODA
is notified, and conducts an investigation and a weed risk assessment. Agency staff
debates attempting to eradicate this new threat to Oregon’s agriculture and
natural resources. The long lived-seed is a problem, and chances of successful
eradication are low. No one involved makes the connection to the contaminated
soybean shipment that arrived 15 years ago. A new weed has established in
Oregon.
This scenario is not going to play out this
time, at least not in Oregon. We don’t think it is possible to contain 2
million specks of dust in 500 tons of soybeans.
As I write this, the containers are
still sitting on the dock in Portland, and the importer is trying to find
another state that will accept them and a transportation/processing procedure
USDA will approve. Fifty-two more containers of organic soybeans are en route
from China.
If you’re wondering why the United
States, the largest producer and a major exporter of soybeans, is importing
soybeans, you’re not alone. Ships containing soybeans must pass each other on
the oceans going opposite directions. Globalization makes for crazy trade
patterns—and efficient transport of invasive species. This story is getting
depressing, I think I’ll go eat something—maybe I’ll BBQ those organic chicken
breasts.
Dan Hilburn
