The perils of pulling ... weeds.
Looking for weeds may sound like drudgery, but for Rick Bennett it has been an adventure amid the crumbling of the Soviet Union and Communist Eastern Europe.
Bennett, an Agricultural Research Service plant pathologist, now receives Christmas cards from his scientific collaborators in Russia-a sign of softening relations that took some of the thorns out of his search for weeds. But before that transformation occurred, Bennett found that searching for weeds was prickly business.
Since 1989, Bennett has spent about 18 months in more than a dozen European countries and the former Soviet Union, walking along roadsides in Romania, trudging through fields in Hungary, and sitting in the back of a Soviet military truck while being escorted through half a dozen former Soviet republics.
Bennett's looking for weeds with names like spurges and thistles, and for the disease-causing organisms that infect them. From numerous trips in 1989, 1990, and 1991, Bennett brought back more than 80 organisms that attack weeds in the United States. Several of these organisms are prime candidates as biological control agents-natural organisms that are environmentally safe alternatives to chemical herbicides.
Many of these weeds-such as leafy spurge, Euphorbia esula L, and yellow starthistle, Centaurea solstitialis-are thought to have originated in Europe and been brought here more than a century ago by immigrants who packed plants onto their ships when they set sail for America. In that soil, however, were weed seeds that would also find a new home in this country.
The trouble is, the natural enemies of those weeds-such as insects and fungi-were left behind, or died on the voyage. So these imported weeds and others have swept across the United States, thriving without natural enemies. Since leafy spurge was first recorded in Massachusetts in 1827, it has spread across 2.5 million acresmostly in the northern Great Plainsand costs ranchers an estimated $35$45 million in damage each year.
Yellow starthistle, since it was first recorded in California in 1869, now infests about 8 million acres in that state alone.
Without knowing it, the immigrants changed the natural balance of plants in the New World, giving these new weeds the upper hand. Helping to restore the natural order is Bennett's job. Among his tools are an aspirator, which he uses to collect fungal spores from weeds; petri dishes and test tubes in which he stores the organisms; and a portable microscope that he uses to identify them.
Bringing back weeds and their accompanying diseases is more complicated than it sounds. Because a fungus that Bennett finds in Romania doesn't already live in the United States, he can't simply bring it back and let it loose. He must get special permits to bring the organism back home, and it must be carried inside several sealed containers to make sure it won't escape if one of the containers breaks.
Those containers must then be transported into a high-tech quarantine lab at the agency's Foreign DiseaseWeed Science Research facility in Frederick, Maryland. Bennett and colleagues must study the organism under strict quarantine regulations inside that lab, where air and watereven toilet and sink waste-are sterilized before they leave the lab. Anyone entering must change into lab clothes and shower and shampoo before leaving.
And the research payoff takes time. It can take up to 10 years to thoroughly study an organism and gain the necessary approval to release it in the United States. Much of that time is used to make sure other plants aren't affected by the foreign disease-causing organism. For example, there are 22 genera and 115 known species of the Euphorbiaceae family that are indigenous to the United States. (This family includes leafy spurge.) He must grow as many of those species as possible in the quarantine lab and expose them to whatever foreign organism he collects; if any of these plants shows signs of infection, the organism can't be used.
"We can only use organisms that are extremely specific to a certain plant species," Bennett says. "A lot of the organisms that I find can't be used in biocontrol because they attack plants other than the weed we're trying to control."
Aside from the scientific hurdles, bringing the organisms back to the United States sometimes means convincing foreign police and security guards that you're really only on a scientific expedition.
That isn't easy. The nature of Bennett's work makes him seem suspicious to the eastern European peasants and police in the outlying villages where he spends most of his time. Most American tourists tend to visit European cities, taking in museums, cathedrals, and other urban attractions, but Bennett heads for the remote countryside where the weeds are.
"I'm always along roadsides or in fields, digging around, taking pictures, collecting, and isolating pathogens," he says. "My portable microscope almost always draws suspicion. In fact, customs agents in Romania took it apm|c once. They thought it was a camera containing microfilm."
Bennett often traveled by rental car in Europe, but not in the former Soviet Union. There, he was transported by the best available vehicle-a Soviet military truck, inside a canvas-covered compartment with only a tiny window and a buzzer. "If we were lucky enough to see any weeds out that window, we'd push the buzzer to signal the driver to stop. Then we would collect pathogens until it was time to return to camp, which consisted of several military-style tents."
There are few, if any, hotels and restaurants in the rural areas of the Soviet republics, and living and working conditions are harsh. On one visit to the former Soviet Union, he and his Russian scientific collaborators had to wait 2 days to simply get gasoline for the truck.
As an American traveling and working alone in Eastern Europe, Bennett sometimes faced additional problems dealing with local police who were not accustomed to unfamiliar foreigners working in the countryside. An encounter in Czechoslovakia was typical. There, he and scientist Massimo Cristofaro, formerly an ARS entomologist based in Rome, were digging in a field of weeds when stopped by police. "We spent about 30 minutes trying to explain what we were doing-which was difficult because the police didn't speak English and we didn't speak Czech," he says. Such confrontations were common in 1989.
"A lot of times, I'd let them look through my microscope to let them see that there wasn't microfilm in it," Bennett says. "Luckily, the word scientist sounds the same in eastern European languages, so most of the time I could eventually get my point across."
Making that point wasn't always easy-especially in Romania, which, before the fall of the Ceausescu regime in December 1989, was one of the more hard-line Communist countries. Not only were security guards particularly suspicious, but food there was often scarce-as it was in many of the countries he visited. He had to stand in line for a handful of potatoes. A loaf of bread he bought was so hard he used it to prop up a table.
But Romania was one of the best places to look for weeds, because of its location near the Ukraine along the Black Sea-the area where leafy spurge is thought to have originated. It's also a good place to search for weeds because of local farming practices; they don't intensively plow their fields-meaning it's a weed searcher's dream come true.
But getting to the weeds was a challenge. In 1989, as a condition for conducting research in Romania before the revolution, Bennett and Cristofaro had to travel to predetermined places on approved roads. Their hotelseven the exact rooms-were arranged in advance. "If we deviated from the approved routes, we could be in for trouble."
Even following the rules didn't always help. While trying to leave Romania after a trip in 1989, he and Cristofaro were detained at the airport by security guards. Their passports were taken, their luggage was snatched from conveyor belts and searched, and they were interrogated for about an hour. Just when it seemed they might be detained for several days, a high-ranking official entered and let them go. There was only one flight leaving Romania each day, and they barely made it. "They told us never to come back."
But they did-and to a markedly different reception. Ironically, during that next trip in the spring of 1990after the fall of Ceausescu-the "same guards hugged us and said, 'Welcome! We love Americans."
Despite all the obstacles, the trips were well worth the trouble from a scientific standpoint. In more than a half-dozen countries, including Greece, Italy, Austria, Switzerland, Hungary, Romania, and Czechoslovakia, he found fungi, called Uromyces, that infect leafy spurge. One species, U. scutellatus, is a prime candidate for bringing that weed under control because, based on early lab studies, it appears to be specific to just leafy spurge. Scientists have known about the organism for several years, but progress has been slow. Bennett is now the only federal scientist working on the fungus.
U. scutellatus literally covered leafy spurge plants in Romania with black spores, called teliospores. The infected plants don't flower and don't produce seeds-effectively blocking reproduction, stunting growth, and deforming the plant stems. The fungus doesn't infect seeds, which explains why it never stowed away aboard the immigrants' ships with the weed seeds.
Since November 1990, Bennett has been studying U. scutellatus under quarantine at the Frederick lab. The main stumbling block so far is that it has been difficult to gerrrnnate the fungal spores in the quarantine greenhouse. Bennett has been trying to duplicate the fungus' native climate, by determining the best conditionstemperature, moisture, light, and other factors-under which to germinate the spores.
He's found that compounds produced by leafy spurge plant roots stimulate germination of the U. scutellatus teliospores. He's also determined that optimal conditions for germination include 24 hours of continuous daylight, at a temperature between 20(deg)C and 22(deg)C.
Germination is also enhanced when the teliospores are exposed to some naturally occurring organic compounds, such as benzonitnle and beta ionone. These aromatic compounds are naturally produced by a wide variety of plants and are effective spore stimulators.
Bennett expects it may take up to 5 years to test other Euphorbia species related to leafy spurge, to make sure that they will not become infected by U. scutellatus. Then field studies will be necessary, so it could be a few more years before the organism is released to control leafy spurge in the United States. Until now, only insects have been released as biocontrol agents for leafy spurge.
Bennett and his colleagues are also studying other organisms for controlling other weeds. Several species of the Puccinia fungus are also under study for controlling yellow starthistle, purple starthistle (Centaurea calcitrapa), spotted knapweed (C maculosa), diffuse knapweed (C diffit. sa), and musk thistle (C thoermeri).
Plant pathologist William Bruckml, also based at the Frederick lab, has been studying a musk thistle rust called Puccinia carduorum for several years and is awaiting approval from USDA's Animal and Plant Health Inspection Service to allow release of the organism in the United States. Such approval could come later in 1992 and would make P. carduortttn only the second foreign disease organism ever intentionally released in the United States.
The first release of a foreign pathogen to control weeds in North America was in 1976, when the rest P. chondrillina was released to control skeletonweed, Chondrilla juncea, in California. That release was also made by the Frederick lab, in cooperation with the California Department of Food and Agriculture, and has been a major success in controlling skeletonweed.
Meanwhile, Bennett plans to continue his foreign travels. He and ARS range scientist Robert Masters of the agency's Wheat, Sorghum, and Forage Research Unit in Lincoln, Nebraska, are scheduled to take an exploration trip in May and June 1992 to collect leafy spurge in Russia, Ukraine, Romania, Hungary, and other parts of Eastern Europe. The goal: To confirm the origin of leafy spurge and collect additional pathogens. Scientists have long suspected that area to be its origin, but they will verify that by bringing back leafy spurge varieties and comparmg them to types collected across the United States. They'll use a genetic fingerprinting technique to make the matches.
"Once we determine the origin of leafy spurge, we can intensify our search for new pathogens. U. scutellatus is the best we've found so far, but there may be others. It's like putting together a puzzle. We still need more pieces."
Finding those pieces may become easier, given the recent changes in Eastern Europe and the former Soviet Union. But until he goes back, Bennett won't know whether his biggest challenge will be avoiding thistle thorns. -By Sean Adams, ARS.
Rick Bennett and William Bruckart are at the USDA-ARS Foreign Disease-Weed Science Research LaboratoW, Fort. Detrick, Bldg. 1301, Frederick, MD 21702. Phone (301) 6197344.
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|Title Annotation:||includes related article on biocontrol guidelines; plant pathologist Rick Bennett searches for weeds in Communist Eastern Europe|
|Date:||May 1, 1992|
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