Field Notes: What’s in the Woods Today? September 20, 2018

by Area Forester Lisa Deaton

Boogie Woogie Aphids

Near the end of August, beech blight aphids, Grylloprociphilus imbricator, appear on American beech trees.  They are easiest to find by locating patches of black sooty mold on the ground underneath infested beech trees.

sooty mold lo res

In the photo above, the orange fungus on the right was the first thing I noticed.  Once I saw the sooty mold to the left, I looked up, and voilà, a branch full of wooly-looking aphids!

single branch snow

These are always a surprise to see during the heat of summer because they look so much like snow.

The fun part of encountering these aphids is waving your hand over the top of the branch and watching them wave their bodies back and forth in an effort to scare off predators.  That is how they earned the common name of boogie-woogie aphids.  You can see them do the boogie woogie in this video:

Like many sap-sucking insects, beech blight aphids take in more sugar than they need, and excrete the excess as honeydew.  The black sooty mold grows on any surfaces covered with honeydew, such as the base of the tree below.

tree trunk

The aphids and mold do very little harm to their host beech trees.  On pages 15-16 of our January 2013 issue of Forest Health Review, forest health specialist Chris Asaro explains all of the intricate relationships between the aphids, trees, ants, and different molds produced.

Now is a great time to explore nearby woods and look for colonies of boogie woogie aphids on American beech trees.  They seem to be present in great numbers in Gloucester County this year.

Field Notes: A Galling History

by Urban Forest Conservationist Jim McGlone

While leading a forest hike with a landowner and group of her friends, I was brought to a small group of pin oaks that had many of the growths pictured here.

Galling History

The landowner was concerned that it was a disease that would spread and kill all her trees.

This growth, and others like it, are called galls.  Galls form when an insect, usually a small wasp, lays its eggs in a twig.  When the eggs hatch, the larvae give off chemicals that cause the tree to produce these woody swellings to protect the growing larvae.  This particular one is called an oak horn gall.  As the larvae grow older the gall grows thinner-walled, hollow horns.  The adult wasps eventually leave the gall through these horns.

In addition to causing the tree to grow these woody lumps, the chemicals given off by the larvae cause the tree to make more defensive chemicals and store them in the galls.  In oaks, one of the primary defensive chemicals is called tannin, a compound that is very useful to people.  It is probably best known for its use in tanning leather.  But it also creates a rich dark pigment when combined with Iron sulfate.  When mixed with water, this pigment creates a highly prized ink called iron gall Ink.

Oak horn galls and other oak galls played an important role in the history of the United States.   In 1776, Thomas Jefferson and the other founding fathers knew this and used Iron gall ink when writing the Declaration of Independence, the U.S. Constitution and the Bill of Rights.

So, to answer to the landowner’s concerns, galls cause only minor damage to trees.  But, in 1776, oak galls did major damage to the British empire!

Field Notes: What’s in the Woods Today? Note. 8, 2017

Snack Time

by VDOF Area Forester Lisa Deaton

Last week I was asked to see if a 16-year-old loblolly pine plantation had grown large enough for a commercial thinning.

I was perplexed to find what looked like pieces of honeycomb on the ground.  There were no large hollow trees nearby, just young, solid pine trees.honeycomb

Then I noticed that there were several pieces of it scattered around a nearby hole in the ground. yellowjacket hole

Also, the nest pieces were paper-like and not made of wax.  Yellowjackets build nests in the ground, so perhaps a skunk or raccoon dug up this nest to eat the wasp larvae inside.  I am embarrassed to say that after 30 years of being allergic to yellowjackets, I’ve just learned that they are wasps, and not bees.

I walked a little further and saw empty soybean pods on the ground. soybeans

A number of animals and birds enjoy eating soybeans, but why were these in the middle of the woods?  I looked up, and realized I was fairly close to a soybean field (in the direction of the shining sun).

looking towards field

Here is one more photo from these woods of something mentioned in last week’s post:  a buck rub, where a white-tailed deer had rubbed its antlers against a young hardwood tree.buck rub

Pretty is as Pretty Does: The Tale of an Emerald Insect Eating its Way Across Virginia

 

“They look so pretty!” That’s what I said the first time I saw an adult emerald ash borer (EAB). But I soon learned from our VDOF Forest Health team that this green insect’s destruction is anything but pretty.

EAB came to the United States from Asia, was first discovered in Northern Virginia in 2008 and is boring its way through ash trees from Michigan to Virginia. “Adult ash borers are metallic green beetles that can be seen flying around the tops of ash trees in late spring and early summer,” VDOF Forest Health Manager Lori Chamberlin said. “These beetles lay eggs on ash bark, and the larvae that hatch tunnel into the tree and feed under the bark. This disrupts the flow of water and nutrients within the tree – effectively choking it to death.”

No ash tree native to Virginia is resistant to EAB, according to Chamberlin. And, unless they are treated before or very early in the infestation, all ash trees that are infested will eventually die.

Hope for Landowners

But there is an arsenal to push these invasive insects back.  “We recommend either a stem injection or a soil drench,” said Chamberlin. “But the time to do this is now, because once an ash tree has lost more than 30 percent of its canopy, it’s too late to save the tree.”

Chamberlin recommends that landowners contact a certified arborist to discuss the treatment options, their costs and the timing of these treatments.

Chemical treatment is effective and most appropriate for high-value landscape trees. Unfortunately, treatment is not normally effective in a forest setting. According to forest survey data, ash makes up approximately two percent of Virginia’s forests. However, it can comprise a significant portion of individual forest stands, especially in riparian and mountainous areas. If you own forestland with a large component of commercially valuable ash, the VDOF recommends discussing your forest management options with a professional forester. Options may range from conducting a silvicultural harvest to doing nothing and leaving the dying/dead trees as wildlife habitat. Check out additional information about professional consulting foresters working in the Commonwealth.

Cutting Edge Push Back

I went out this summer with Lori Chamberlin, VDOF Forest Health Specialist Katlin Mooneyham and University of Virginia Forest Health Intern Kendra Counts  to try out an EAB management method in Cumberland State Forest (check out the video up top).  It was hot; there were mosquitoes and waist-deep poison ivy. But the work this team accomplished will go a long way towards learning how best to fight back against EAB.

As we waved off mosquitoes and navigated the underbrush, Chamberlin and Mooneyham explained that biological control is the most effective effort that we can use in controlling these beetles as they move through forested settings where other control options are not viable. The only other real shot we have at controlling EAB is use of insecticides, but in forests that is difficult because of the amount of ash present and the expense of treatment for that many trees.

“Biological control is a key tool in the integrated pest management toolbox for controlling invasive species,” said Mooneyham. “When we’re faced with a widespread attack, such as we are currently experiencing in Virginia with EAB, we need all the help we can get.”

I like to refer to this summer’s experience as “releasing the hounds,” but we actually released parasitoid wasps. Two releases occurred this summer, one in Whitney State Forest in Warrenton and one in Cumberland State Forest in Cumberland. At Whitney 600 Oobius agrilus (a species that attacks EAB eggs) and 855 Tetrastichus plannipennis (a species that attacks EAB larvae) were released. At Cumberland 400 Oobius agrilus and 403 Tetrastichus plannipennis were released. These wasps pose no threat to humans –– they don’t sting and in fact they are very tiny (really…check them out in the video!).  Tetrastichus plannipennis is only 3-4 mm in size and Oobius agrilus is similarly very small.

And don’t worry; they’re safe (unless you’re an EAB), legal and extensively tested. VDOF received approval to release thIMG_0813ese wasps from USDA APHIS since testing in quarantine showed that they were not a threat to other native insects or animals. This also means that since the wasps are so species-specific for their prey that their population rises and falls along with changes in EAB populations!

 

 

 

 

The VDOF Forest Health staff continues to monitor the establishment of these predators over the next few years at these two sites and hopefully more releases on other state lands will follow. Ultimately, the release of these parasitoids is one of the efforts VDOF is pursuing to protect ash throughout Virginia and gives hope that EAB’s march through our state can be slowed. F

Click here to learn more about EAB or these parasitoids.