Biological Control and Invasive Species

This week I attended an awards ceremony celebrating the success of a biological control project. Cereal leaf beetle (CLB), an invasive grain pest, arrived here a decade ago. Pesticide use in grain fields increased steadily. A team of scientists and regulators from Oregon and Washington banded together to bring in parasitic wasps that feed on CLB. 

One parasite attacked CLB larvae, the other its eggs. The larval parasite established, and CLB parasitism rates now are up to 100% in some fields. Pesticide use against CLB has dropped dramatically. CLB will always be here, but hopefully at levels below economic thresholds.

That is the good news. There is some bad news. CLB continues to spread. It was reported for the first time in Jackson County this spring. The CLB biological control team has already released parasites there. Hopefully, they will establish there, too, and suppress CLB populations.

This is an example of biological control done well. The parasites are specific to the non-native invasive species target, and once established, they reduce the use of pesticides.

Biological control does not always work so well; there are plenty of examples of biological control done badly. Sometimes the introduced biological control agent itself has become a harmful invasive species. Many of the biological control-gone-bad examples around the world were introductions of generalist parasites or predators that were released by amateurs, though the US Department of Agriculture (USDA) has made a few mistakes, too.

Two examples from Oregon spring to mind: The multi-colored Asian lady beetle, a USDA-release, has become a pest because it overwinters in large numbers in houses. There is concern that it may be displacing native lady beetles. 

Rynocyllus conicus, a weevil introduced as a biological control for invasive thistles also feeds on native thistles. Both of these were introduced decades ago when biological control wasn’t well regulated. Now official releases only happen after years of host-specificity testing. We’ve gotten better at biological control.

Islands are especially vulnerable to invasive species and provide numerous examples of the dark side of biological control. Here are some examples from Bermuda where I worked before coming to Oregon.

1.) Lizards were introduced to control fruit flies. The lizards preferred other prey and soon there were lizards everywhere. Kiskadees (a jay-like bird) were introduced to eat lizards, but they were noisy and preferred baby bluebirds. Then the fruit flies and the bluebirds disappeared, but the lizards and kiskadees persist to this day!

2.) Cane toads were introduced to control cockroaches. That didn’t work, but they eat honeybees by the hundreds and love monarch butterflies!  These enormous toads become thin, dinner plate-sized road ornaments when they encounter cars. There is an old Bermuda joke that goes like this:  “Why did the toad cross the road? To see his flat mate.”

Congratulations to USDA, Oregon Department of Agriculture, Washington State University, and Oregon State University for their award. Your work proves that non-native biological control agents have a place in the battle against invasive species.

Dan Hilburn

Invasive Species and the World Cup

We have a World Cup fanatic on our staff (Helmuth Rogg, the Insect Program Supervisor). His bad case of soccer fever has infected some of the other staff, including me—though compared to him, the rest of us have a mild case. At first glance there is no obvious connection between the World Cup and invasive species, but think again.

Global trade and travel is how most invasive species move from continent to continent. A huge event that draws people from all over the world is sure to involve some unseen hitchhikers. Spectators arriving by plane, ship, rail, car, and even on foot may be traveling with invasive company. Here are some examples from closer to home:

Planes arriving at PDX from certain airports (e.g., Louisville, KY) carry live Japanese beetles. ODA inspectors look at the high-risk planes and find live beetles every year. This pest is on the State’s list of the 100 Worst Invasive Species to keep out, and once again this summer, there will be a treatment project at PDX to eliminate a small population that has established there.

Ships and boats carry invasive species in ballast water and attached to their hulls. The recent discovery of an invasive sea squirt (Didemnum vexillum—also on the State’s 100 Worst List) in Winchester Bay and in Charleston harbor shows how Oregon is subject to invasion by sea.

Pests can travel by rail, too. Several years ago. imported fire ant (100 Worst List) was found in a railroad car carrying cotton seed for cattle feed when it arrived in Oregon.

Cars and trucks also carry non-traditional hitchhikers. An Australian scientist came up with an ingenious way of quantifying “car-borne flora.” He collected the sludge from a commercial car wash, extracted the oil, and sifted out the seeds. When he planted them, an astonishing 18,000 seedlings appeared representing 259 species——predominantly weeds (Wace 1977). I wish someone would do this study in Oregon.

Even pedestrians can transport invasive species. World Cup spectators in South Africa should take notice of this story (Lowe 1999): “I returned from one trip to Africa to find dried mud caked to my sandals. Examining it closely I found a trove of organic riches: bits of straw, grass seed husks, flakes of snail shell, four seeds and some fungal treads bearing spore heads—a forensic record of my trip lay scattered before my eyes. One of the seeds was nearly as big as a dried pea, and I thought of sprouting it to see what it was, but a tiny insect later drilled an exit hole in one side.”

Many of the foreign World Cup spectators will no doubt return from Africa with carved masks and other wooden handicrafts. It wouldn’t be unusual for ODA to get a call from a concerned traveler who has noticed little piles of sawdust accumulating under their souvenir. The powder post beetles that are slowly turning their handicraft into sawdust have probably already been transported around the world, but there are other species we’d be wise to keep out so we’re happy to receive the calls.

So what’s a traveler to do? The fanatics aren’t going to stay away from the World Cup, nor should they. You and I and all the other travelers/drivers/boat owners can make a difference by cleaning our shoes, vehicles, and boats before leaving one area to go to another. It is that simple. If everyone made a habit of doing that, there would be a lot fewer hitchhikers traveling with tourists, motorists, and World Cup fans. Oh and if your souvenir shows signs of living inhabitants, put it in the freezer overnight——that usually takes care of the problem.

Lowe, T. 1999. Feral Future. Penguin Books Australia Ltd. 380 pgs.

Wace, N. 1977. Assessment of dispersal of plant species – the car-borne flora in Canberra. Proc. Ecol. Soc. Aust. 10:168-186.

A Tale of Three Nurseries

The U.S. program to address sudden oak death (Phytophthora ramorum) is stuck in a rut. This week Oregon Department of Agriculture (ODA) found an infection at a large Oregon nursery that ships plants all over the country. This is not the first time this has happened, and unless something changes, it won’t be the last. Here is a short story to illustrate the problem.

Once upon a time there were three nurseries. As long as people could remember, these nurseries had been growing and selling plants to satisfied customers. The nurseries were called: Clean and Green, Pretty Good Plants, and Cuttin Corners. 

 Then one day, something new and sinister appeared—a plant disease called Sudden Oak Death, or Phytophthora ramorum. No one knew where disease came from, but it killed a lot of oak trees in places where it became established. 

The disease spread into the nursery industry. Regulatory officials became alarmed. Everybody wanted to protect oak trees from the sinister disease. The elders remembered previous epidemics that wiped out elm trees and chestnut trees. Concern spread like a shadow over the whole land. 

What could they do? At first many States enacted quarantines, each one different from the others. An ugly patchwork of regulations emerged. No one was happy. Federal authorities saw the problem and stepped in to keep things from getting worse. Federal money flowed in to pay for inspectors to inspect and test the plants at Clean and Green, Pretty Good Plants, Cuttin Corners, and all the other nurseries in the land.

  

The inspectors looked and looked, and every now and then they found the disease hiding among the plants at a nursery. It was very hard to find because, except on oak trees, its symptoms looked like common leaf spots. Every time the disease was found, bad things happened and people got mad. Thousands of dollars worth of plants were destroyed, and all the regulatory officials were notified. Time and again, inspectors fanned out across the land in search of the sinister disease because they didn’t want their oak trees to die. In spite of everyone’s best efforts, this continued to happen, and the reputation of the nursery industry began to suffer.

As time went by, the federal government and regulatory officials across the land grew disillusioned. Nothing changed.

One person knew what needed to be done. Ima Sampler, the inspector for Clean and Green, Pretty Good Plants, and Cuttin Corners, had lots of experience with nurseries and plant diseases. She had noticed a pattern.

After years of inspecting nurseries and testing plants for Sudden Oak Death, she could predict with a high rate of accuracy which nurseries were likely to be infected. Clean and Green rarely had any disease problems. In fact, Ima had trouble finding symptomatic plants to sample there. Clean and Green was a very good nursery with excellent management practices. Diseases weren’t an issue at Clean and Green. 

Pretty Good Plants was also a good nursery. They knew about Sudden Oak Death, and they had made some changes in their management practices. Unfortunately the owner, Joe Average, couldn’t afford all the best management practices that he’d learned about in a free online course at http://ecampus.oregonstate.edu/workforce/phytophthora/. Ima crossed her fingers when she inspected Pretty Good Plants; she’d seen similar nurseries develop disease problems, including sudden oak death.

Cuttin Corners was Ima’s nightmare. The owner, Standin Still, had been in business for a long time. Management practices had barely changed at all since the nursery started. Cuttin Corners was still buying stock from whoever offered the cheapest price, plants were often standing in puddles of water, and at Cuttin Corners, they reused pots without sterilizing them. Ima crossed her fingers, held her breath, and said a little prayer every time she inspected Cuttin Corners. It was only a matter of time before P. ramorum showed up there, and it was going to spread rapidly when it did. 

Ima had a dream.

Ima’s dream was that all nurseries that shipped plants out-of-state operated like Clean and Green. She realized that it was going to cost money for Pretty Good Plants to get there, but it was certainly possible. The money that Pretty Good Plants lost in dealing with the P. ramorum infection at their nursery would have paid for a steam pot sterilizer.

It also dawned on Ima that unless all the shipping nurseries in the land adopted best management practices (BMPs), the problem of diseases being vectored by nursery stock would never go away.

 Ima realized that Cuttin Corners was never likely to adopt the necessary BMPs, at least while Standin Still was in charge. In Ima’s opinion, Cuttin Corners shouldn’t be shipping plants to other states anyway.

 Ima’s dream seemed out of reach. A new system of nursery certification was needed, one that required a different, higher standard of plant health for nurseries shipping interstate.

Nursery industry, government leaders, and state regulatory officials still didn’t want the oak trees to die, but many of them worried about what would happen when the federal money stopped paying for inspections and testing. Unfortunately, there was no additional money to pay for a conversion to another system. So nothing changed.

  

This story is still being written. Here is the ending I’d like to see.

  

Eventually it dawned on several key people that the status quo was not sustainable. It was time to take the lessons learned by Ima Sampler, Guy Visionary, and Joe Average, develop a plan, and get started moving toward a sustainable system.

  

Two big hurdles stood in their way right from the beginning. The first was settling on national standard BMPs. Luckily, several researchers around the country had been studying the effectiveness of BMPs. Taking the best science available, a new national certification standard for shipping nurseries was hammered out. Initially, not everyone liked it, or thought it was necessary, but the industry leaders, scientists, and government officials worked together to educate the doubters. The second hurdle was greater.

  

Many nurseries were not in a position financially to make the changes necessary to reach the national standard. Again working together, the nursery industry, federal government, and State Regulatory officials devised a plan to help. They took the money that was being spent on inspecting and testing Clean and Green, and other nurseries already meeting the new national standard, and instead used it to provide help for the nurseries like Pretty Good Plants that needed upgrades. As more and more nurseries reached the new shipping standard, fewer and fewer needed intensive inspections and testing.

The government, with the support of the nursery industry, set a deadline of 5 years to get the new national nursery certification system in place. There was considerable angst at the beginning, but by working together, the industry and the government sold the idea to Guy Visionary, Joe Average and thousands of other nursery owners all over the land. State regulatory officials liked the provision that inspections and SOD testing would continue at nurseries not meeting the national standard. By enacting a uniform standard across the board, nobody was put at a competitive disadvantage. Customers and retail nurseries didn’t really notice the difference except plant quality seemed to be a lot more consistent.

  

After 5 years, the new national nursery certification system was in place. It was voluntary, except for nurseries shipping interstate. Shipping permits were only available for nurseries meeting the new national standard. Everyone agreed that risk of moving dangerous plant diseases on nursery stock was greatly reduced. The SOD inspection and testing program morphed into a nursery standards program that was less costly and more effective.

All the people were glad that the trees were still there.

  

The End

Dan Hilburn

Mosquito Fish and Spider Mite Farms

I toured a couple of very interesting farming operations in Klamath Falls this week. Both used natural geothermal hot water. One of them produced spider mites, the other tropical fish. Both have connections to invasive species.  

Farming spider mites seems like a bad joke, but someone has to produce the eggs that serve as a food source for production of predator mites. This farm produces zillions of spider mites on lima beans in a series of large greenhouses, all kept at a toasty 90 degrees Farenheit by the abundant hot water. Each week, they fill the equivalent of 17 Dixie cups full of nearly microscopic spider mite eggs. Predator mites feast and grow on the eggs at a separate location.

Eventually, strawberry growers and other farmers and gardeners buy these biological control agents and use them instead of chemicals to keep spider mites below economic thresholds. That is good thing.

These same commercially-available predator mites negated an attempt at biological control of gorse (an invasive weed) on the south coast of Oregon a few years back. The Oregon Department of Agriculture (ODA) imported a gorse spider mite to eat the gorse. The biological control agent established readily and seemed to be stressing the plants, but the mite population soon crashed when a non-native predator mite showed up. The predator mite was the same species sold commercially as a biological control agent. It was a case of one biological control agent eating another!

The second farm produced cichlids for the tropical fish trade and tilapia for grocery stores. Both are raised in 85 degree Farenheit water in open ponds. This farm got its start several years back when a vector control official approached them about raising mosquito fish (Gambusia) in the warm water. Mosquito fish look like guppies, and, like a lot of fish, they eat mosquito larvae. Unfortunately, under favorable conditions, they can become invasive and displace native fish. Australia has serious Gambusia problems.

In Oregon, mosquito fish are allowed only in artificial water bodies not connected to natural systems. That is a reasonable policy considering the risks and benefits. More information on mosquito fish in Oregon is available at: http://www.dfw.state.or.us/fish/diseases/docs/backgrounder_WNV_gambusia.pdf

Dan Hilburn