CORVALLIS, Ore. – The analysis of a termite entombed for 100 million years in an ancient piece of amber has revealed the oldest example of “mutualism” ever discovered between an animal and microorganism, and also shows the unusual biology that helped make this one of the most successful, although frequently despised insect groups in the world.

The findings were made by George Poinar, an Oregon State University researcher and international expert on life forms found in amber. It was just published in Parasites and Vectors, a professional journal.

This particular termite was probably flying around while mating in a wet, humid tropical forest in what is now Myanmar during the Early Cretaceous period – the age of the dinosaurs. It may have been attacked by a bird or somehow torn open, and then it dropped into the sticky, oozing tree sap that would later become amber, providing an opportunity for the biology of this ancient insect to be revealed in a way that would otherwise have been impossible.

Out of its wounded abdomen spilled a range of protozoa, which even then were providing a key function for the termite – they helped it to digest wood. Between animals and microorganisms, this is the earliest example ever discovered of “mutualism,” which is one type of symbiotic relationship in which two species help each other.

“Termites live on cellulose, mostly from the dead wood they chew, but they depend on protozoa in their gut to provide the enzymes that can digest the wood,” Poinar said. “These protozoa would die outside of the termite, and the termite would starve if it didn’t have the protozoa to aid in digestion. In this case they depend on each other for survival.”

Even more primitive termites may have fed on a range of things they could digest themselves, Poinar said, but eventually they acquired protozoa that dramatically increased their ability to digest cellulose, and through evolutionary processes they came to depend on it.

Today, modern termites are one of the world’s most pervasive and successful insect groups, with about 2,300 known species, mostly in tropical settings, busily at work chewing wood or other plant fiber that protozoa help to digest. They have important ecological roles, helping to create habitat, build soil fertility, recycle nutrients and serve as food for many predators. As a social species similar to ants, some colonies can have 20 million individual insects. And they also cause massive amounts of damage every year to wood structures in much of the world.

Their dependence on these protozoa is now well understood, and the process isn’t always pretty.

Somewhere on the evolutionary scale the termites began producing a liquid that contained protozoa that they would excrete. The termite offspring in turn consume the feces and thereby gain the protozoa in their digestive systems.

It took time for all of this to get worked out, the study indicated. The successful establishment of protozoa in the termites required them to withstand the chemical and physical conditions inside the alimentary tract, use the gut contents as a food source, cause no damage to the host and be carried through successive stages and generations.

But by the different species each specializing at what they do best – the termite eats, the protozoa digests – the two groups have both had extraordinary evolutionary success.

“The relationship between termites and protozoa is very close and has been stabilized now for a very long time because of its obvious value,” Poinar said. “It’s exciting to understand that this classic example of mutualism has been going on now for at least 100 million years.”

As well as outlining this age-old example of mutualism, the new study revealed 10 new fossil flagellate species of protozoa, a new species of termite, a new genus of fossil amoeba and 14 additional trophic and encysted protist stages.

Poinar for many years has studied life forms and other material found trapped in amber. As a semi-precious stone that first begins to form as sap oozing from a tree, amber has the unique ability to trap very small animals or other materials and – as a natural embalming agent – display them in nearly perfect, three-dimensional form millions of years later. This phenomenon has been invaluable in scientific and ecological research, and allows researchers to characterize the biology of ecosystems that existed millions of years ago.

The amber that contained the termite used in this study came from a mine first excavated in 2001 in the Hukawng Valley in Myanmar, in a formation that was between 97 and 110 million years old.

Source: Oregon State University

Key Largo, Fla. – April 27, 2009 – A new study appearing in Restoration Ecology describes a novel technique for reattaching large sponges that have been dislodged from coral reefs. The findings could be generally applied to the restoration of other large sponge species removed by human activities or storm events.

20 specimens of the Caribbean giant barrel sponge were removed and reattached at Conch Reef off of Key Largo, Florida in 2004 and 2005 at depths of 15m and 30m. The sponges were affixed to the reef using sponge holders consisting of polyvinyl chloride piping, which was anchored in a concrete block that was set on a plastic mesh base.

Though the test area endured four hurricanes during the study period, 62.5 percent of sponges survived at least 2.3-3 years and 90 percent of the sponges attached in deep water locations survived. The sponges reattached to the reef after being held stationary by sponge holders for as little as 6 months.

Large sponges may be damaged by a variety of natural events and human activities including severe storms, vessel groundings and the cutting movements of chain or rope moved along with debris by strong currents. After these events, detached large sponges are commonly found, still alive and intact, between reef spurs on sand or rubble where they slowly erode under the action of oscillating currents.

“The worldwide decline of coral reef ecosystems has prompted many local restoration efforts, which typically focus on reattachment of reef-building corals,” says Professor Joseph Pawlik of the University of North Carolina-Wilmington, co-author of the study. “Despite their dominance on coral reefs, large sponges are generally excluded from restoration efforts because of a lack of suitable methods for sponge reattachment.”

These sponges, which often exceed reef-building corals in abundance, can be more than 1m in diameter and may be hundreds or thousands of years old. The success of past attempts at reattaching sponges, which used cement or epoxy, has been limited because adhesives do not bind to sponge tissue. When damaged or dislodged, large sponges usually die because they are unable to reattach to the reef. The results of the study show that these sponges have the ability to reattach to the reef if they can be properly secured.

Source: Wiley-Blackwell

Fire must be accounted for as an integral part of climate change, according to 22 authors of an article published in the April 24 issue of the journal Science. The authors determined that intentional deforestation fires alone contribute up to one-fifth of the human-caused increase in emissions of carbon dioxide, a heat-trapping gas that increases global temperature.

The work is the culmination of a meeting supported by the Kavli Institute for Theoretical Physics (KITP) and the National Center for Ecological Analysis and Synthesis (NCEAS), both based at the University of California, Santa Barbara and funded by the National Science Foundation (NSF).

The authors call on the Intergovernmental Panel on Climate Change (IPCC) to fully integrate fire into their assessments of global climate change, and consider fire-climate feedbacks, which have been largely absent in global models.

The article ties together various threads of knowledge about fire, which have, until now, remained isolated in disparate fields including ecology, global modeling, physics, anthropology and climatology.

Increasing numbers of wildfires are influencing climate as well, the authors report. “The tragic fires in Victoria, Australia, emphasize the ubiquity of recent large wildfires and potentially changing fire regimes that are concomitant with anthropogenic climate change,” said David Bowman of the University of Tasmania. “Our review is both timely and of great relevance globally.”

Carbon dioxide is the most important and well-studied greenhouse gas that is emitted by burning plants. However, methane, aerosol particulates in smoke, and the changing reflectance of a charred landscape each contribute to changes in the atmosphere caused by fire. Consequences of large fires have huge economic, environmental, and health costs, report the authors.

The authors state, “Earth is intrinsically a flammable planet due to its cover of carbon-rich vegetation, seasonally dry climates, atmospheric oxygen, widespread lightning and volcano ignitions. Yet, despite the human species’ long-held appreciation of this flammability, the global scope of fire has been revealed only recently by satellite observations available beginning in the 1980s.”

They note, however, that satellites cannot adequately capture fire activity in ecosystems with very long fire intervals, or those with highly variable fire activity.

Jennifer Balch, a member of the research team and a postdoctoral fellow at NCEAS, explains that there are bigger and more frequent fires from the western U.S. to the tropics. There are “fires where we don’t normally see fires,” she said, noting that it is in the humid tropics that a lot of deforestation fires are occurring, usually to expand agriculture or cattle ranching. “Wet rainforests have not historically experienced fires at the frequency that they are today. During extreme droughts, such as in 97-98, Amazon wildfires burned through 39,000 square kilometers of forest.”

Balch explains the importance of the article: “This synthesis is a prerequisite for adaptation to the apparent recent intensification of fire feedbacks, which have been exacerbated by climate change, rapid land cover transformation, and exotic species introductions–that collectively challenge the integrity of entire biomes.”

The authors acknowledge that their estimate of fire’s influence on climate is just a start, and they highlight major research gaps that must be addressed in order to understand the complete contribution of fire to the climate system.

Balch notes that a holistic fire science is necessary, and points out fire’s true importance. “We don’t think about fires correctly,” she said. “Fire is as elemental as air or water. We live on a fire planet. We are a fire species. Yet, the study of fire has been very fragmented. We know lots about the carbon cycle, the nitrogen cycle, but we know very little about the fire cycle, or how fire cycles through the biosphere.”

“The large and diverse group of authors on this paper typifies an increasing trend across many sciences,” said Henry Gholz, an NSF program director. “NSF explicitly supports this by funding “synthesis centers,” such as NCEAS and KITP. Instead of focusing on generating new data, these centers synthesize the results of literally thousands of completed research projects into new results, theories and insights. The conclusions of this paper–that fire is important to the global carbon cycle and global climate, and that our ignorance about fire at this scale is vast–and could not have otherwise been obtained.”

Source: National Science Foundation

DURHAM, N.C. – A new study of storm-related deaths from a super cyclone that hit the eastern coast of India in 1999 finds that villages shielded from the storm surge by mangrove forests experienced significantly fewer deaths than villages that were less protected.

The study, conducted by researchers at the University of Delhi and Duke University, analyzed deaths in 409 villages in the poor, mostly rural Kendrapada District of the Indian state of Orissa, just north of the cyclone’s landfall.

“Our analysis shows a clear inverse relationship between the number of deaths per village and the width of the mangroves located between those villages and the coast,” said Jeffrey R. Vincent, Clarence F. Korstian Professor of Forest Economics and Management at Duke’s Nicholas School of the Environment.

“Taking other environmental and socioeconomic factors into account, villages with wider mangroves suffered significantly fewer deaths than ones with narrower or no mangroves,” Vincent said. “We believe this is the first robust evidence that mangroves can protect coastal villages against certain types of natural disasters.”

Vincent conducted the analysis with Saudamini Das of the University of Delhi’s Swami Shradanand College. Their findings appear in a paper in this week’s online early edition of The Proceedings of the National Academy of Sciences.

Mangroves are dense forests of trees and shrubs that grow in brackish, low-lying coastal swamps in the tropics and subtropics. In 1944, mangroves covered nearly 31,000 hectares of land in Kendrapada District and the average village had 5.1 kilometers of mangroves between it and the coast. Since then, nearly half the area has been cleared, mostly for rice production. Today, the average width of mangroves between the villages and the coast has shrunk to 1.2 kilometers.

The 1999 storm, which made landfall on Oct. 29, killed nearly 10,000 people, more than 70 percent of whom drowned in its surge.

Using statistical models, Das and Vincent predicted there would have been 1.72 additional deaths per village within 10 kilometers of the coast if the mangrove width had been reduced to zero.

“This is a measure of the life-saving impact of the mangroves that remained in 1999,” Vincent said. “It implies that they cut the death toll by about two-thirds.”

Although mangroves evidently saved fewer lives than an early warning issued by the Indian government, the retention of the remaining mangroves in Orissa is economically justified, Vincent believes, even without considering the many other environmental benefits they provide, such as acting as nurseries for economically and environmentally vital fisheries, or sites for ecotourism. Previously published estimates of Indians’ willingness to pay to reduce the risk of accidental deaths are higher than Das and Vincent’s estimate of the cost of saving lives in Orissa by retaining mangroves.

The study does not assess mangroves’ ability to reduce deaths from tsunamis, Vincent cautions, because of key differences in their wave dynamics. Storm surges have shorter wave lengths than tsunamis, and relatively more of their energy is found near the surface of the water. Mangroves’ ability to protect villages against tsunamis has been a point of controversy in the scientific and policy communities since the 2004 Indian Ocean tsunami. Das and Vincent designed their study to overcome criticism leveled at studies examining the effects of mangroves on that disaster.

Source: Duke University

Unprecedented dense deployment of EarthScope USArray Transportable Array, Flexible Array and Magnetotelluric instruments is providing data that are being used to develop a new generation of high-resolution Earth models and understanding of structure and processes. Fresh observations:

• Earthscope Gradiometry: Charles A. Langston, et al., will discuss a new tool for understanding seismic waves by taking a snapshot of how seismic waves propagate across the United States. Rather than evaluate how the ground shakes as seismic waves pass through, this tool looks directly at the seismic wave and how it behaves. Using a newly developed theory, this research offers an entirely new way to consider seismic waves, opening new fields of study.

• Evolution and Effects on the Western U.S. of the Yellowstone Hotspot and Mantle Plume: The Yellowstone hotspot resulted from interaction of a mantle plume with the overriding N. America plate producing a ~800-km wide, ~300-m high topographic swell centered on Yellowstone and produced the 800 km-long, 17 Ma Yellowstone-Snake River Plain volcanic field. Scientists have observed an unprecedented episode of caldera uplift, up to 7 cm/yr from 2004-2008 — an accelerated rate of 2-3 times the rate recorded in historic time that is consistent with magma intrusion rate of 0.1 km^^3/year, or tens of times larger than the average annual rate of mapped uplift of the caldera. Extrapolating the location of the Yellowstone mantle-source southwestward to an initial position at 17 million years ago beneath eastern Oregon and the southern LIP Columbia Plateau basalt field, suggests a common mantle source for these features. Robert Smith, et al., suggest that the original plume ascended vertically behind the subducting Juan de Fuca plate, but at ~12 Ma became entrained in faster mantle flow beneath continental lithosphere and became tilted into its present configuration.

Source: Seismological Society of America

Washington, D.C.— The Earth’s original atmosphere held very little oxygen. This began to change around 2.4 billion years ago when oxygen levels increased dramatically during what scientists call the “Great Oxidation Event.” The cause of this event has puzzled scientists, but researchers writing in Nature* have found indications in ancient sedimentary rocks that it may have been linked to a drop in the level of dissolved nickel in seawater.

“The Great Oxidation Event is what irreversibly changed surface environments on Earth and ultimately made advanced life possible,” says research team member Dominic Papineau of the Carnegie Institution’s Geophysical Laboratory. “It was a major turning point in the evolution of our planet, and we are getting closer to understanding how it occurred.”

The researchers, led by Kurt Konhauser of the University of Alberta in Edmonton, analyzed the trace element composition of sedimentary rocks known as banded-iron formations, or BIFs, from dozens of different localities around the world, ranging in age from 3,800 to 550 million years. Banded iron formations are unique, water-laid deposits often found in extremely old rock strata that formed before the atmosphere or oceans contained abundant oxygen. As their name implies, they are made of alternating bands of iron and silicate minerals. They also contain minor amounts of nickel and other trace elements.

Nickel exists in today’s oceans in trace amounts, but was up to 400 times more abundant in the Earth’s primordial oceans. Methane-producing microorganisms, called methanogens, thrive in such environments, and the methane they released to the atmosphere might have prevented the buildup of oxygen gas, which would have reacted with the methane to produce carbon dioxide and water. A drop in nickel concentration would have led to a “nickel famine” for the methanogens, who rely on nickel-based enzymes for key metabolic processes. Algae and other organisms that release oxygen during photosynthesis use different enzymes, and so would have been less affected by the nickel famine. As a result, atmospheric methane would have declined, and the conditions for the rise of oxygen would have been set in place.

The researchers found that nickel levels in the BIFs began dropping around 2.7 billion years ago and by 2.5 billion years ago was about half its earlier value. “The timing fits very well. The drop in nickel could have set the stage for the Great Oxidation Event,” says Papineau. “And from what we know about living methanogens, lower levels of nickel would have severely cut back methane production.”

What caused the drop in nickel? The researchers point to geologic changes that were occurring during the interval. During earlier phases of the Earth’s history, while its mantle was extremely hot, lavas from volcanic eruptions would have been relatively high in nickel. Erosion would have washed the nickel into the sea, keeping levels high. But as the mantle cooled, and the chemistry of lavas changed, volcanoes spewed out less nickel, and less would have found its way to the sea.

“The nickel connection was not something anyone had considered before,” says Papineau. “It’s just a trace element in seawater, but our study indicates that it may have had a huge impact on the Earth’s environment and on the history of life.”

Source: Carnegie Institution

MADISON, WI, APRIL 7, 2009 — A recent study conducted in the Midwestern United States examined the effects of harsh wet conditions on both cultivated and uncultivated soils, vastly advancing the knowledge of water’s effects on aggregation. Soil aggregation is an important soil attribute that is related to the physical-chemical state of the soil, and is one of the essential processes that determine soil quality. During the wet season in the U.S. Midwest, upland soils are often under water for days or weeks, causing oxygen depletion, or reducing conditions, which may in turn affect the chemistry of the soil-water system and, consequently, soil aggregation. Loss of soil aggregation impacts agriculture by decreasing soil quality and crop production.

Recently, soil scientists investigated how changes in the reduction-oxidation (redox) status of the soil can impact soil aggregation during short-term ponding conditions. The group included Alfredo De-Campos, a former graduate student from Purdue University, and Amrakh Mamedov and Chi-hua Huang, from USDA Agricultural Research Service, National Soil Erosion Research Laboratory at West Lafayette, IN. Results from this study were published in the March/April, 2009 issue of Soil Science Society of America Journal.

To carry out the research, six different upland soils, three cultivated and three uncultivated, with different organic carbon and similar mineralogy were incubated up to 14 days in an anaerobic biogeochemical reactor. After each treatment, the soil solution was analyzed for metals and dissolved organic carbon. A simple laboratory procedure that measures the degree of aggregate breakdown during wetting was used to determine aggregate stability of the incubated soil samples.

The research revealed that the aggregate stability of upland soils was decreased under reducing conditions from short-term water ponding. The decrease in aggregate stability reached approximately 20% during a 14-day ponding period, which is quite significant in terms of soil disaggregation. Changes in redox sensitive elements, alkaline metals, and dissolved organic carbon under reducing conditions contributed to the decrease in aggregate stability.

Overall, the aggregate stability of cultivated soils was more affected by the reducing conditions than that of uncultivated soils. This indicates that the management system plays an important role in the stability of aggregates.

The use of natural soils without addition of chemicals simulated a realistic field situation when aerobic upland soils remained saturated for several days and the oxygen level depleted to a minimum, causing reducing conditions. The authors believe that once the reducing reactions take place in the field and disaggregation has occurred, the process will not reverse itself because the natural drainage will carry away the released chemicals and the chemistry of the soil-water system will not return to the original state. The disintegrated aggregates may clog the soil pores and further degrade the soil structure.

However, reducing conditions only occur for short periods of time during the wet season in upland soils, whereas aggregation processes operate for several months causing re-aggregation of soil particles. The long-term irreversibility in soil disaggregation caused by the short-term reducing conditions remains an open question.

Source: Soil Science Society of America

DURHAM, NC – Rainforest reserves – even those disturbed by roads – provide an important buffer against fires that are devastating parts of the Brazilian Amazon, according to a new study by a trio of researchers at Duke University published April 8 in the open-access, peer-reviewed journal PLoS ONE.

“Our findings show that reserves are making a difference even when they are crossed by roads,” said lead author, Marion Adeney, a PhD candidate at Duke University’s Nicholas School of the Environment. “We already knew, from previous studies, that there were generally fewer fires inside reserves than outside – what we didn’t know was whether this holds true when you put a road across the reserve.”

Fire is one of the chief causes of deforestation in tropical rainforests. Fires in humid tropical forests are always caused by people, Adeney says – they typically start on farms or ranches and spread to the nearby forest. Since tropical forest trees have no natural protection against fire, even a small fire can kill most of the trees.

Nearly 90 percent of fires occur within 10 kilometers of a road, a key factor, Adeney says, in explaining why fires are much more common and concentrated in the southern Amazon, where roads are more numerous.

Determining whether reserves with roads provide protection against deforestation caused by fires was critical, she explains, because the pace of road-building has accelerated in recent years in many parts of the Brazilian Amazon rainforest, including in many reserves. Especially important are the region’s indigenous reserves, which cover five times the area of fully protected parks. Despite having roads and settlements, many of these indigenous reserves contain ecologically important areas of rainforest still largely unaffected by the human development in surrounding areas.

“There is a lot of discussion about how to curb deforestation and fire as new roads are built or paved into these forests,” says Adeney’s co-author and faculty co-advisor, Stuart Pimm, Doris Duke Professor of Conservation Ecology at Duke’s Nicholas School.

To assess what degree of protection reserves with roads provide against these fires, Adeney, Pimm and Norm Christensen, professor of ecology at the Nicholas School, analyzed ten years of satellite-detected fire data from the entire Brazilian Amazon.

Overall, they found no significant difference in fire incidence between sustainable-use reserves, indigenous reserves and protected parks. Location and timing were found to be much more important factors than type of reserve, Adeney notes. Fires were more likely to occur during El Nino years, as a result of drought. But, the increase in fire in El Niño years was greater outside than inside of reserves, suggesting that reserves are also buffering against these climate effects. “Still, although there are overall many fewer fires inside than outside reserves, we found that reserves in highly impacted areas still experienced more fires than reserves in remote areas. Large and remote reserves, not surprisingly, had the fewest roads and the fewest fires,” she says.

“This reinforces the importance of reserves for protecting forest cover in the Amazon” says Pimm. “Our results show that even inhabited reserves can be an effective tool to reduce fires, even when they have roads built through them.”

Source: Public Library of Science.

Credit: Photo by Matt Friedman

Large size and a fast bite spelled doom for bony fishes during the last mass extinction 65 million years ago, according to a new study to be published March 31, 2009, in the Proceedings of the National Academy of Sciences.

Today, those same features characterize large predatory bony fishes, such as tuna and billfishes, that are currently in decline and at risk of extinction themselves, said Matt Friedman, author of the study and a graduate student in evolutionary biology at the University of Chicago.

“The same thing is happening today to ecologically similar fishes,” he said. “The hardest hit species are consistently big predators.”

Studies of modern fishes demonstrate that large body size is linked to large prey size and low rates of population growth, while fast-closing jaws appear to be adaptations for capturing agile, evasive prey—in other words, other fishes. The fossil record provides some remarkable evidence supporting these estimates of function: fossil fishes with preserved stomach contents that record their last meals.

When an asteroid struck the earth at the end of the Cretaceous about 65 million years ago, the resultant impact clouded the earth in soot and smoke. This blocked photosynthesis on land and in the sea, undermined food chains at a rudimentary level, and led to the extinction of thousands of species of flora and fauna, including dinosaurs.

The fossil fish on the left is not related to the modern swordfish on the right, which is for sale at a fish market. Nevertheless, the swordfish developed a size and shape similar to the fossil fish and appears to be vulnerable to extinction for some of the same reasons that the fossil form was vulnerable: it is a large predator.

Credit: Photo by Matt Friedman

Scientists had speculated that during that interval large predatory fishes might have been more likely than other fishes to go extinct because they tended to have slowly increasing populations, live more spread out, take longer to mature, and occupy precarious positions at the tops of food chains. Today, ecologically similar fishes appear to be the least able to rebound from declining numbers due to overfishing.

To build the database he needed to test this prediction, Friedman traveled around the world measuring the body size and jaw bones of 249 genera of fossil fishes that lived during the late Cretaceous. These kinds of direct measurements are possible in fossil fishes because many are represented by complete, articulated individuals. This is unlike the fossil record of most other vertebrates, where bones, teeth and other parts of the skeleton are often scattered and found in isolation.

This study is the first to test this theory with hard data and to quantify the relationship between body size, jaw function and vulnerability of fishes during the Cretaceous extinction, according to Friedman.

“Anyway you sliced it, the data showed that if you were a big fish with a fast bite you were toast,” he said.

Ironically, today’s large fishes with fast bites evolved relatively shortly after the end-Cretaceous extinction, apparently filling the functional and ecological roles vacated by the victims of that mass extinction. Although the two groups of fishes are not related to each other, their fates may end up being similar.

The paper is called “Ecomorphological selectivity among marine teleost fishes during the end-Cretaceous extinction” and will appear in issue 13 of PNAS. In it, Friedman describes the results of his study as robust because the large-bodied, predatory fishes that are disproportionately devastated also have the best fossil records. “In other words, we can be convinced that these forms really do die off here, and that their disappearance can’t be chalked up to a lousy fossil record,” Friedman noted.

Nevertheless, fossil fishes are not well studied because paleontologists, as a group, tend to be drawn to other animals, such as dinosaurs. Therefore, many large-scale patterns of fish evolution remain unclear.

The fossil fishes included in the study are diverse in form, and range in length from about 20 feet to less than one inch.

“This study demonstrates that fossil datasets are germane to modern diversity and evolution by allowing us to calibrate what characteristics might relate to extinction vulnerability today,” Friedman said. “Echoes of the end-Cretaceous extinction reverberate 65 million years later.”

Source: University of Chicago Medical Center

CHAMPAIGN, IL—Herbicide drift, which occurs when pesticides “drift” from the targeted application area to a nearby non-targeted area, is a particular concern in Midwestern regions of the United States. In the Midwest, where the topography is relatively flat and large-scale farms and agriculture production facilities reside side-by-side with housing developments and woodlands, herbicide drift can have an impact on wildlife, livestock, timber production, and quality of life for human neighbors.

A study published in a recent issue of HortScience evaluated the effects of field corn herbicides on white oak seedlings. White oak, a popular landscape and forest species native to the eastern United States, has been suffering from an abnormality called “leaf tatters”, which give the leaves a lacy appearance. Leaf tatters in white oak trees have been reported in states from Minnesota, south to Missouri, and east to Pennsylvania. This problem is not just aesthetic; it can affect a substantial portion of a tree’s canopy, reducing the health of the tree. Leaf tatters make affected trees more susceptible to other stressors such as adverse environments, air pollution, and pests, and can make containerized oak seedlings unmarketable.

Jayesh B. Samtani, John B. Masiunas, and James E. Appleby from the Department of Natural Resources and Environmental Sciences at the University of Illinois at Urbana–Champaign, studied the effects of field corn herbicides on white oak at different stages of development. The experiment simulated herbicide drift using herbicides commonly applied to corn and previously found to injure plants.

“We chose to treat white oak seedlings at the swollen bud, leaf unfolding, and expanded stages of leaf growth”, Masiunas explained. “Previously, it was suspected that insect feeding, environmental factors, or herbicide drift could cause leaf tatters. Our preliminary research eliminated insect feeding as a cause of leaf tatters and found trees near agricultural fields were most likely to be injured. Based on our observations, we theorized that leaf tatters were caused by drift from herbicide applications before or at corn planting.”

The researchers found that visual injury to white oak seedlings was dependent on year, herbicide treatment, concentration, growth stage, and rating date. The type, intensity, and persistence of injury symptoms differed among herbicides. The study results indicated that herbicide applications near white oak should be timed before leaf unfolding or after the expanded leaf stages.

This research is the first to document leaf tatters injury from exposure of oaks to chloroacetanilide herbicides (using dose rates of 1%, 10% and 25%). The scientists recommend further research to determine how multiple occurrences of leaf tatters affect white oak stands, how atrazine influences leaf tatters, and if lower rates of chloroacetanilide herbicides cause injury.

Source: American Society for Horticultural Science