Tree-Killing Insects Adapting to Warmer Cities

By Megan Gannon, News Editor | LiveScience.com 

 

Bizarre-looking bugs known as scale insects may be tiny but they can take down an oak tree. Considered pests, the creatures tend to flock to cities where they weaken, and in some cases, kill trees by sucking out their sap.

A new study shows that scale insects are found in big numbers in populous regions because they have adapted to the heat of urban areas. The pests threaten to become a bigger problem as climate change drives temperatures up, researchers warn.

"We now have a better understanding of why trees in urban areas are infested by so many of these pests," study researcher Steve Frank, an assistant professor of entomology at North Carolina State University, said in a statement. "And if climate change causes temperatures to rise in forests, as we expect, we may see scale insects becoming a much bigger problem for ecosystem health."

Frank and his colleagues analyzed the Raleigh, N.C., populations of the oak lecanium scale insect (Parthenolecanium quercifex), which feeds exclusively on oaks. By looking at temperature maps of the city, the researchers found that the scale populations were as much as 800 percent higher in the warm zones.

The team then collected scale insect egg sacs from both hot and cool zones and incubated them in hot and cool greenhouses. In the hot greenhouse, the egg sacs from the warmest urban zones produced almost four times as many insects as the egg sacs from cooler urban zones.

To try to explain this trend, the researchers looked at the prevalence of parasites and the fertility rates among the insects from both hot and cold zones of the city, but they did not find any significant differences. The scientists concluded that the bugs have locally adapted in response to urban warming.

"The scale insects in the hotter urban zones appear to have adapted or acclimated to the higher temperatures in urban environments," study researcher Emily Meineke, a doctoral student at NC State, said in the statement. "Theoretically, that adaptation would also allow them to take advantage of warmer temperatures that may result from climate change."

The urban heat island effect can make temperatures several degrees warmer in a city than its surrounding rural areas, as clusters of roads and buildings are very good absorbers of the sun's rays. Rising numbers of scale insects in cities could spell trouble for city trees, which can provide some environmental benefits like cooling through shade and carbon sequestration. And if global temperatures continue to rise, scale insects could spread outside cities and infest more rural trees, the researchers warn.

Their findings were detailed in a study published online last week in the journal PLOS ONE.
Follow Megan Gannon on Twitter and Google+. Follow us @livescience, Facebook & Google+. Original article on LiveScience.com.

EAB University webinar "Fall is for EAB Planning"

"FALL IS FOR EAB PLANNING"

Cliff Sadof, Purdue University
September 11, 2012, 11 a.m. Eastern

Though the preferred time for protecting ash trees with insecticide treatments has passed this year, fall is a great time to take stock of your EAB situation and make plans for next year. Fall is prime time to update your ash inventory and identify the trees worth saving, so you can be ready in the spring when EAB treatments are the most effective. Cliff Sadof of Purdue University will review the latest tools to help you get your community concerned about their ash trees so that you can muster the resources you need to fight EAB next year.

You can access the webinar by going to: http://connect.msu.edu/eab-university/ and login as a guest. If you've never participated in these webinars, it is a good idea to get on a day or two early to see if you can access the site. If not, you may want to contact your server administrator to seek permission to get into the webinar (usually a situation that occurs with participants from municipal and federal organizations).

Emerald Ash Borer Resource

From the Minnesota Department of Agriculture:  Emerald Ash Borer Insecticides: Label Guidance for Use Limits

Frequently Asked Questions Regarding Potential Side Effects of Systemic Insecticides Used To Control Emerald Ash Borer

February 2011. Emerald Ash Borer Information Network

Research and extension specialist have prepared a new publication that addresses frequently asked questions and concerns regarding the use of systemic insecticides to control emerald ash borer.

Emerald Ash Borer Control Recommendations

From Phil Nixon, University of Illinois Entomologist, published in the University of Illinois Home, Yard, and Garden newsletter

A new publication has been produced on control recommendations for emerald ash borer (EAB). This is co-authored by entomologists from Ohio State University, Michigan State University, Purdue University, University of Wisconsin, and University of Illinois. Dr. Dan Herms, Ohio State University, and Dr. Deb McCullough, Michigan State University, are responsible for most of the content, but all five universities added to and endorse the publication.

The significant change in these control recommendations is the use of emamectin benzoate (Tree-Age) as the insecticide of choice injected into the tree every two years. Recent research, primarily conducted by Michigan State University and Ohio State University, shows that a high level of control is achieved for at least two years with each application of emamectin benzoate. This level of control is high enough to save trees even with very high pest pressure.

Other methods of control, including imidacloprid (Merit, Imicide, Xytect) soil and trunk injection and soil drench, and dinotefuran (Safari) trunk spray, provide a level of control adequate for lower pest pressure. These insecticides are more useful as a preventative before EAB becomes numerous in an area or after heavy infestations have ended and most untreated trees have died. In both of these situations, there are fewer beetles present to attack the trees, allowing less effective insecticidal control to be adequate. A basis for this recommendation is that many of the trees annually treated with insecticides other than emamectin benzoate in high EAB pressure areas of Michigan and Ohio have died.

We are still not recommending control in an area until EAB has been found within 15 miles. Recent research continues to indicate that most trees with up to 40% dieback from EAB will survive if treated with emamectin benzoate.

Emamectin benzoate approved for use against Emerald Ash Borer in Illinois

Press Release from the Illinos Department of Agriculture
April 22, 2008

NEW TOOL APPROVED IN FIGHT AGAINST DEADLY BEETLE

SPRINGFIELD, Ill. – Illinoisans will now have an effective alternative to tree removal in their arsenal against the Emerald Ash Borer, a deadly wood-boring beetle that has plagued Illinois and North America long before its initial discovery in 2002.

The Illinois Department of Agriculture on April 15th, approved a special local need request for the use of Tree-ägeTM, an insecticide touted as the most effective chemical weapon against EAB. Nearing 100 percent effectiveness, the product, developed by Swiss agrochemicalcompany Syngenta and Massachusetts firm Arborjet, has an active ingredient called emamectin benzoate which is injected directly into the ash tree’s vascular system where EAB larvae feast. The direct injection affects only the beetle larvae and will not harm anything coming into contact with the tree such as butterflies, birds and squirrels.

After yearlong preliminary studies, Michigan and most recently, Indiana officials have approved the chemical. Based on results in Michigan, preliminary evidence suggests that a single treatment could provide up to two years of control. Ideally intended as a preventative treatment for healthy, non-EAB-infested trees,TreeägeTM is most suitable for trees in close proximity to EAB-infested areas.

“IDA encourages property owners to consult with a certified arborist or tree care company to discuss treatment pricing and other options suitable for their situation,” says Warren Goetsch, bureau chief of Environmental Programs. “Cost will be a factor for most homeowners. This tool will most likely be used by golf courses and other landscape areas where entire canopies will be devastated affecting local commerce.”

First discovered in Illinois in June 2006, EAB has since been confirmed in communities within Kane, Cook, LaSalle and DuPage counties. A quarantine has been issued for the northeastern-most area of the state in an attempt to prevent its spread. EAB quarantine provision compliance is urged for all contractors and public works officials around the state, and especially those within the EAB quarantined area in all or parts of the 18 northeastern-most counties of the state.

The quarantine prohibits the removal of the following items from regulated areas:
• The emerald ash borer in any living stage of development.
• Ash trees of any size.
• Ash limbs and branches.
• Any cut, non-coniferous firewood.
• Bark from ash trees and wood chips larger than one inch from ash trees.
• Ash logs and lumber with either the bark or the outer one-inch of sapwood, or both, attached.
• Any item made from or containing the wood of the ash tree that is capable of spreading the emerald ash borer.
• Any other article, product or means of conveyance determined by the Illinois Department of Agriculture to present a risk of spreading the beetle infestation.
• waste haulers must cover regulated material from an infested area during transport through EAB flight season, which is from June through August.

Anyone convicted of moving prohibited items from the quarantine area without prior certification by an Illinois Department of Agriculture nursery inspector may be fined up to $500.How the emerald ash borer arrived in Illinois is unknown, but the department suspects it
may have been transported here in contaminated firewood. To avoid the accidental introduction of the beetle to new areas, the department encourages Illinoisans to purchase only locally-grown
nursery stock and locally-cut firewood. Anyone who suspects a tree has been infested is urged to contact the department or their village forester for a consultation.

The emerald ash borer is difficult to detect, especially in newly-infested trees. Citizens should watch for metallic-green beetles about half the diameter of a penny on or near ash trees that are showing signs of disease or stress. Other signs of infestation in ash trees include D-shaped holes in the bark of the trunk or branches and shoots growing from its base. Anyone who suspects a
tree has been infested is urged to contact their county Extension office. For more information, visit www.IllinoisEAB.com on the internet.

What's New in EAB?

from www.Emeraldashborer.info

Emamectin Benzoate Pesticide Now Registered for Use
in Treating Ash Trees for Emerald Ash Borer (EAB)
**states seeking registration for this new management strategy**
Emamectin benzoate:

* Is the name of a new insecticide that can be used to protect valuable landscape ash trees from EAB in Michigan.

* A special 24(c) registration request for this product was approved by the Michigan Department of Agriculture on March 27, 2008.

* It represents a new tool for protecting valuable landscape ash trees from emerald ash borer.

* The product will be sold as Tree-äge™ (pronounced "triage") and should be available for use this spring.

* Emamectin benzoate has not previously been used to protect ornamental trees. A similar product has been used in salmon farming and in California for some fruit and vegetable crops. A related product is used in veterinary medicine.

* It can be purchased and applied only by trained, certified arborists and landscapers.

* The product is applied as a trunk injection at the base of an ash tree. It is not sprayed on the tree nor applied to the soil.

* Like any systemic insecticide, this product must be transported through the trunk and into the canopy. Therefore, it will usually be more effective in a tree that is reasonably healthy than in a tree that has already been severely injured by EAB larvae.

To find out more on emamectin benzoate and the current research done with this insectide at Michigan State University, go to What's New in April

From the Chicago Tribune: China's ash trees may hold salvation for U.S. cousins

By Gerry Smith and Tara Malone | Tribune reporters


Glenn Weiler sounded like he was delivering a eulogy, speaking in the past tense used by arborists who now deem the ash tree's demise inevitable, its enemy unstoppable.

"Ash was so nice because it handled the tough soils," said Weiler, who stopped growing the species at his Zion tree nursery two years ago. "It's becoming a thing of the past, I think."

But some researchers still see a future for the ash tree, and they believe it lies somewhere in the Chinese countryside. Six years after the emerald ash borer was first spotted in the Midwest, researchers are turning their attention across the globe, to the region where the tiny, metallic-green beetle originated.

One ongoing effort—reminiscent of past efforts to rescue the American elm—is to identify Asian ash trees that have developed natural defenses against the pest, then develop a hybrid species for the American landscape that will withstand the devastating beetle.

"It's reflective of the idea that the emerald ash borer is here to stay and it's going to take a long-term solution," said Dan Herms, an associate professor of entomology at Ohio State University who is involved in the project.

Although still years from development, the pursuit of borer-resistant ash trees has become part of the evolving strategy for combating the ash borer, which has killed about 25 million trees across the Midwest and Canada.

Hope in Far East
Officials in Michigan found some hope in the Far East last fall, when they began unleashing tiny, stingless Chinese wasps that kill the pest's eggs and larvae.

And this spring, Illinois officials are rigging traps designed to snag the flying beetles after sweeping inspections and a state quarantine have helped contain their spread.

Also, researchers have been encouraged by the early success of a new pesticide that may become widely available this year. Researchers have found the pesticide, which contains the chemical emamectin benzoate, kills more than 99 percent of ash borer larvae in treated trees and virtually all adult ash borers that feed on them.

Meanwhile, evidence of the pest continues to emerge in ash trees across the Chicago area since first appearing two years ago in a Kane County subdivision. Last month, work crews with the Kane County Forest Preserve District cut down and burned nearly 100 trees infested with the ash borer.

Already, the telltale white larvae of the beetle have been spotted in ash trees everywhere from south suburban Hazel Crest to the tree-lined North Shore.

With few proven strategies for eradicating the ash borer, researchers across the Midwest are trying to find out how Asian ash trees manage to live with their enemy.

Later this year, Kris Bachtell plans to collect female ash tree seeds in China's Gansu province and join other researchers who are trying to identify, then replicate, the DNA in Asian ash trees with natural defenses against the ash borer.

"The best chance to find resistance is to go where the pests and plants co-evolved," said Bachtell, director of collections and grounds at the Morton Arboretum in Lisle.

The approach, which could take several years to yield results, was once used to revive another species after a similar scourge.

Learning from elms
During the 1950s, the American elm was nearly done in by Dutch elm disease, a plague that felled hundreds of trees in Chicago's Grant Park and nearly every elm on the campus of the University of Illinois at Urbana-Champaign.

But then researchers, led by the Morton Arboretum's George Ware, began experimenting with cross-breeding Asian elms in the late 1970s. Since then, the arboretum has introduced thousands of disease-resistant elms across the country.

Ware, a dendrologist at the arboretum, remains hopeful a similar effort could lead to a resurgence of the ash tree in the American landscape.

"It'd be a glorious thing if someone said, 'This is a species of ash that the ash borer simply does not like,' " he said. "The search is intense now, so I think there will be some kind of breakthrough."

Above all, officials said they've learned one important lesson from the outbreaks of both Dutch elm disease and the emerald ash borer: diversification.

Elms once represented about 40 percent of the tree population in metropolitan Chicago, but they were replaced after the Dutch elm outbreak by the ash tree, which makes up about one-fifth of Chicago's trees.

Now, as communities plant new trees where ash once stood, they're drawing from different species to guard against another pest destroying entire blocks of trees. Many suburbs cap the use of any single species at 5 percent of their total tree stock.

"When elm trees were removed and they replaced them with ash trees, there was a sense of urgency. They just wanted to replace them," said Jennifer Statz, a forester in Wilmette overseeing the removal and replacement of 2,855 ash trees on public lands during the next four years. "Now we've learned that's really not the wisest management choice."

Two years ago, when the emerald ash borer was discovered less than a mile from his Kane County tree nursery, Matt Zerby started bulldozing hundreds of ash trees. This month, Zerby plans to replace some of them with hybrid elm trees, hoping someday he'll be able to plant ash trees again.

"Who knows, maybe 40 years from now we'll have an emerald ash-borer resistant ash tree," Zerby said.