Jeff Mulhollem, Pennsylvania State University
Genes in green ash trees that may confer some resistance to attacks by the emerald ash borer express themselves only once the tree detects the invasive beetle’s feeding, according to Penn State researchers.
Knowing this, geneticists may be able to selectively breed trees to strengthen them and perhaps move the resistance response earlier to ward off the beetles’ onslaught, explained John Carlson, professor of molecular genetics.
Green ash, an ecologically and economically valuable tree species native to eastern and central North America, is under severe threat from the rapid invasion of emerald ash borer, a wood-boring beetle native to Asia. Penn State scientists and others are trying to save the species.
Prior observations in a green ash provenance trial—an experiment to see how plants adapt—planted at Penn State in 1978 by Kim Steiner, professor of forest biology and director of The Arboretum at Penn State, and colleagues in the U.S. Forest Service, show that a very small percentage of ash trees survive emerald ash borer infestations, seemingly because their tissues do not nourish and perhaps even sicken the beetles.
“Emerald ash borer probably entered the provenance trial unnoticed around 2008 and trees started showing symptoms of attack by 2012,” Carlson said. “All but eight or nine of the approximately 1,800 trees that Kim planted have subsequently been killed by the beetles.”
Ash trees succumb after adult beetles lay eggs on their bark. When the eggs hatch, the larvae bore into the bark and feed on the transportation tissues of the tree. This disrupts the movement of nutrients and water within the tree, girdling it and causing death.
“To better understand the response of green ash trees to emerald ash borer, we compared gene expression data for resistant versus susceptible green ash genotypes exposed to attack by the beetles,” said Carlson, director of Penn State’s Schatz Center for Tree Molecular Genetics. “By comparing RNA-sequence data from stems attacked by emerald ash borer to multiple tree tissues under other stresses, we could identify differences in the gene expression profiles specific to emerald ash borer resistance.”
The emerald ash borer is known by entomologists by its acronym: EAB. If you’re an insect aficionado or a tree lover, you likely already know this name. For the rest of you, it’s a name you will know soon enough. It is the cause of arguably the most catastrophic current tree death events in the history of North America.
By Neil Shaw
JOHANNESBURG — One of the world’s largest urban forests is under threat from a tiny beetle.
The polyphagous shot hole borer is thought to have made its way to Johannesburg from Southeast Asia on packing crates or through the trade in plant materials.
Trudy Paap, a forest pathologist at the University of Pretoria, discovered the beetle in the Pietermaritzburg Botanical Gardens last year. She published her discovery in the journal Australasian Plant Pathology, calling it part of “the surge in the global spread of invasive forest pests” because of globalization.
The beetle has since moved to Johannesburg, 200 miles away, and spread across its urban forest, which according to the Massachusetts Institute of Technology initiative Treepedia has the world’s sixth-largest green canopy cover.
Today, many of Johannesburg’s estimated 6 to 10 million trees are dying, a crisis obscured only by the current winter season. Some of the infected trees have the telltale holes the 2-millimeter-long beetle makes in their bark.
“This beetle doesn’t actually eat the trees,” Paap said. Instead it carries a fungus that blocks the vessels that transport water and nutrients, “which ultimately leads to die-back and death of the tree.”
Though scientists don’t know just how many trees have died from the beetles’ invasion, the outlook for Johannesburg is grim: “The city is going to lose a lot of trees.”
The trees do not have an evolved resistance to the polyphagous shothole borer, unlike in Asia where the beetles naturally occur.
It is the older, more established trees that are at risk, said arborist Neil Hill. “So that’s going to leave a gap in the landscape. And if we don’t start to plant straight way with new trees that gap is going to become more and more of a concern as far as urban blight, pollution, aesthetic beauty.”
New research suggests the removal of timber harvest residue during harvesting may be a boon for wild bees, an important step toward better understanding the planet’s top group of pollinators.
The findings are important because bees are the driving force behind $100 billion in global economic impact each year, with insect pollinators enhancing the reproduction of 90 percent of the Earth’s flowering plants, including many food crops.
Insect pollinators are also ecologically critical as promoters of biodiversity. Bees are the standard bearer because they’re usually present in the greatest numbers and because they’re the only pollinator group that feeds exclusively on nectar and pollen their entire life.
Researchers at Oregon State University spent two years studying 28 contiguous 1-acre clearcut sites. They assessed whether the abundance and diversity of wild bees was affected by the removal of timber harvest residue, also known as slash, and the soil compaction that goes along with it.
“Bees are important for biodiversity in managed forest landscapes but we just don’t have a very good handle on them in these areas,” said lead scientist Jim Rivers of the OSU College of Forestry.
The study plots occurred within a managed conifer forest in western Oregon. Each plot received one of five unique treatments, ranging from removing only the boles – tree trunks that are used to make lumber – without compacting the soil at all (no heavy equipment used on the plot) to removing all of the logging slash and compacting the entire plot.
The findings were surprising, Rivers said.
“The combination of the most intense timber residue removal and soil compaction treatment made for the greatest number and diversity of bees,” he said.
By Bob Weber
A massive and uncontrollable buildup of mountain pine beetles in Jasper National Park is starting to explode into commercially valuable forests along its boundaries.
Foresters along the park’s edge have seen a tenfold increase in beetle infestation in just months, and some scientists wonder if Parks Canada could have done more to control the invasion a few years ago.
“They decided to consider the pine beetle a ‘native disturbance agent,”‘ said Allan Carroll, who has studied the beetles since the late 1990s and directs the University of British Columbia’s Forest Science program. “In other words, Jasper was not intending to do much about it.”
No end to pine beetle battle in Alberta, experts say
In an emailed statement, Parks Canada said it has had a beetle management plan for the park since 2015 that includes prescribed burns and tree removal.
Too little, too late, said Carroll.
“Just that hesitation intrinsic to producing a management plan precluded any effective outcomes.”
Insects, both beneficial and disruptive, have always been front-of-mind for the people growing our food. Of particular interest in today’s world are invasives: insects that are not native to a region and whose introduction (whether intentional or accidental) is likely to cause harm to our environment, our economy or human health. Or already has.
A 2016 report in Nature Communication estimates that the annual economic impact of invasive insects on goods and services in North America is at least $27.3 billion. And this, say the authors, is likely an underestimation because determining the economic impact of invasives can be particularly difficult. “Most cost estimates are disparate, regionally focused, cover variable periods and are not always grounded in verifiable data,” write the authors. Additionally, the spread and the impact of invasive insects is likely to increase in coming years due to climate change, rising human population densities and intensifying international trade. But, say the authors, there is a way to minimize the impact: increased surveillance, containment and public awareness. In other words: To protect our local farmers, food systems and economies, we – the general public – need to pay attention to the bugs around us.
In the Microbial Sciences Building at the University of Wisconsin-Madison, the incredibly efficient eating habits of a fungus-cultivating termite are surprising even to those well acquainted with the insect’s natural gift for turning wood to dust.
According to a study published today (April 17, 2017) in the journal Proceedings of the National Academy of Sciences, when poplar wood undergoes a short, 3.5-hour transit through the gut of the termite, the emerging feces is almost devoid of lignin, the hard and abundant polymer that gives plant cells walls their sturdiness. As lignin is notorious for being difficult to degrade, and remains a costly obstacle for wood processing industries such as biofuels and paper, the termite is the keeper of a highly sought after secret: a natural system for fully breaking down biomass.
“The speed and efficiency with which the termite is breaking down the lignin polymer is totally unexpected,” says John Ralph, a UW-Madison professor of biochemistry, researcher at the Great Lakes Bioenergy Research Center (GLBRC) and lignin expert. “The tantalizing implication is that this gut system holds keys to breaking down lignin using processes that are completely unknown.”
By Dennis Pillion
A full-grown Southern pine beetle is still about half the length of a grain of rice, but state and federal forestry officials worry this tiny bug could have a monster impact this year on the state of Alabama’s $11 billion wood products industry.
“With Southern pine beetles, the Latin name (Dendroctonus frontalis) actually means tree killer, and it is,” said Edward Loewenstein, associate professor of silviculture at Auburn University’s School of Forestry and Wildlife Sciences. “It is well-suited to take trees out.”
This year’s concerns are rooted in the large number of trees left stressed or already dying from last year’s record-setting drought. Drought-stressed trees don’t make sap as well as healthy ones, and that sticky sap is the tree’s primary defense against beetles.
By Holly Ramer, Associated Press
They may be down but they’re not out: Damaging insects can emerge from fallen trees and logs for several years after a major storm, according to a U.S. Forest Service study that reinforces long-standing warnings against moving firewood from place to place.
Timber that gets blown down, broken or damaged by wind is often cut and used as firewood, which in turn can enable the spread of invasive, destructive insects that drain the life out of forests from New England to the West Coast.
Such pests are projected to put 63 percent of the country’s forest at risk through 2027 and carry a cost of several billion dollars annually in dead tree removal, declining property values and timber industry losses, according to the peer-reviewed study last year in Ecological Applications.
Researchers were surprised to find that wood harvested even three years after the tornado produced a significant number of insects.
By Deanna Weniger
The emerald ash borer has proved an elusive foe to conservationists. It hides in the tree tops and its larvae stow away under the bark of the ash tree, making early detection difficult.
Scientists have tried a host of methods — purple sticky boxes, yellow pan traps and bark stripping — in a desperate effort to stop the destruction of the invasive wood boring beetle that has killed tens of millions of ash trees in over 20 states.
While the beetle can hide from humans, it’s not as good at hiding from natural predators, such as the smoky-winged beetle bandit, also known as Cerceris fumipennis.
The University of Minnesota Extension office is looking for volunteers to locate and monitor these harmless wasps that build their nests in sandy soil.