Sassafras and Laurel Wilt

We have been involved in monitoring yet another non-native pest causing substatnial tree mortality in the southeastern U.S. Redbay ambrosia beetle (Xyleborus glabratus) was introduced at some point prior to its 2002 detection in coastal Georgia.  At the time, it was found associated with large swaths of dead redbay (Persea borbonia) shrubs. 

Redbay ambrosia beetle bores into stems and innoculates the xylem with a fungus (Raffaela lauricola), which it then cultivates inside the stem in order to feed on.  The growth of the fungus plugs up the xylem, shutting down the ability of that plant to pump water through its stem resulting in the wilting of the entire plant.  The beetle and pathogen are native to Asia and were most likely brought into the U.S. on wood packing material used for international shipping.

For several years, the pest and pathogen seemed to be isolated along the coast of Georgia and South Carolina infesting redbay, but it turns out that this insect likes all members of the Lauraceae family and without getting bogged down in the details we are going to turn our focus on Sassafras albidum, our beloved sassafras trees.  

Dead sassafras trees along a forest edge at Panther Creek S.P. in TN

And the sassafras trees we are focused on do not live along the coastal region of the southeastern U.S., nope these insects have decided to travel and we are now monitoring dead and dying trees as far inland as eastern TN and all the way into Kentucky!  In fairly short order, the insect has brought its fungus away from the coast and into the mountains infesting sassafras trees of all sizes.

A medium-sized sassafras tree with wilting foliage

Xylem staining caused by the fungus growing in the xylem of a ssassafras tree

Scale representation of ambrosia beetle boring holes in cross section of tree stem

Magnified cross section of RAB boring into tree stem

As mentioned earlier, we have been monitoring this pest as it has moved from the coast to the mountains.  We have studied some of its basic ecology and I will be sharing details on an experiment we are installing this summer on mitigating the effects of this insect/pathogen complex.

Hemlock Restoration 2.0

It seems that the first job of any Forester is to plant trees.

Dr. 'Bud' Mayfield planting one of our hemlock seedlings

Our newest hemlock experiment is in the ground!  We are looking at how various light levels in a forest stand affect hemlock seedlings and the woolly adelgid.  In order to investigate these questions we planted hemlocks along a north-south transect in forest gaps and a control group under forest canopy.  The gaps were created as part of a previously implemented silviculture experiment that involved group selection harvests in a method termed "femelschlag" that mimics natural forest disturbance patterns.

One of our 8 planted gap treatments

An eastern hemlock seedling planted in a gap treatment

A Carolina hemlock seedling planted in a gap treatment

Although normally found on different site types, we are planting both eastern and Carolina hemlock side-by-side in this experiment in order to investigate how the two species fair under similar conditions. 

Early morning frost on one of our seedlings

Some of our volunteers planting the end of a gap transect

It was a cold, wet week and perfect for little hemlock seedlings going into the ground.  Less than desirable for the many humans out working to get those trees in the ground though.  We are incredibly thankful for all of the volunteers and extra help we received.  We could not have completed this daunting task without all of you!

Thanks so much to the Hemlock Restoration Initiative staff and volunteers who helped!  Many thanks to our U.S. Forest Service partners with Pisgah N.F. and especially the crew from the Appalachian District. And a hearty thanks to the many other volunteers who braved freezing temperatures, rain, snow, and some steep slopes to help us accomplish all of this! 

Go get 'em silver flies!

We are busy this spring releasing our new biological control agent, the silver fly.

Do you remember that hemlock woolly adelgid has 2 generations each year? Our best predators so far all feed on the fall/winter generation.  So, unless all the adelgid are eaten or die, come spring time a whole new generation emerges to feed and reproduce.  We are hopeful that theses silver flies will put a real hurtin' on that spring generation so we can reduce adelgid levels and relieve the pest pressure on our hemlock trees year round.

A very special thank you to Mr. Darrel Ross at Oregon State University and Mr. Mark Whitmore at Cornell University who have tirelessly worked to collect flies in their native habitat, rear them in the lab, and ship them to us.  As you can see, theses flies are small and fast.  We could not do any of this work without such great cooperators!

Spring means...crawlers

This is the time of year when the progrediens generation of hemlock woolly adelgid (HWA) is out in full force crawling out of their white, woolly ovisacs and looking for a place to settle at the base of a nice green hemlock needle.

HWA crawlers on a hemlock twig, photo taken through a hand lens. 

 Can you see them?  They are all lined up trying to find a place to settle in and feed. 

HWA ovisacs and crawlers on hemlock twig, photo taken through a hand lens.

You can see the sheer numbers of HWA our hemlock trees have to deal with.  We are out this week setting up another round of experiments with silver flies,  an adelgid predator that has shown some promise.  Well, we found the buffet, I hope these flies are hungry!

Winter won't wait...

In the Northern Hemisphere, winter officially starts at the same time every year.  In 2017 it was on a Thursday, December 21st, the shortest day of the year.  The Winter Solstice.  And winter has swept into the Southeastern U.S. with some teeth this year. 

Exhibit A...

The first snow of winter came early in December and gave The Carolinas lots of unexpected snow and cold temperatures.

 

Exhibit B...

Local forecasters did not anticipate this winter storm that caused havoc on New Year's Eve in Asheville, NC.

As these storms and frigid temperatures continue to effect our day to day lives you can take some solace in the fact that hemlock woolly adelgid has it worse than you. 

Snowflakes settle on HWA ovisacs during a blustery morning snow event in Asheville, NC.

Hemlock woolly adelgid does not tolerate temperatures below freezing very well.  The colder our winter gets and the longer it lasts will help our native hemlock trees.  That sure does warm me up...a little...this certainly is hopeful for our beloved hemlock trees.

A target hemlock tree we recently released in the Jefferson NF in VA.

So, be courageous, keep warm, and stay safe through this bitter start to winter. 

Searching for Sirex spp.

We are at it again, setting up wood wasp traps as part of a localized survey to detect native siricids and parasitoids.  A wood wasp native to Europe, Sirex noctilio, has been introduced to parts of the U.S.  For now, the non-native species has only been detected in portions of NY, PA, MI, and VT. Our southern pine species would be prime habitat for these critters though, so we are making attempts to detect the insect. 

 A ridgetop outside of Hot Springs, NC that was burned during fires in spring of 2016.

Our "Lincoln log" style wood wasp trap.

We scheduled our first round of cuts to coincide with typical flight times of local Siricids.  Of course we didn't realize we would be experiencing record high temperatures in October, lugging a chainsaw and gear up steep slopes...

 Moving a tree top off of a steep slope to position next to our trap setup.

Wood wasps love dead and dying pine trees, so we selected an area that recently experienced a stand replacing fire.  The challenge was finding live pine trees that aren't already being colonized.  We were able to find white pine, Virginia pine, and Table mountain pine trees in good condition.

Bud labeling and marking one of our traps.

A live Table mountain pine tree in a stand with mostly dead overstory.

We did this detection survey back in 2015/2016 on 2 different sites with white pine.  We did not detect any of the non-native pest (Great!), but we did not get many of the native siricids either.  The traps will sit out in the woods for approximately 9 months. Then, logs from the traps will be moved into rearing cages where we can monitor what comes out.

Vandals!

In a controlled experiment, as many variables as possible are accounted for, a hypothesis is conceived.  The experiment is carefully planned, laid out, and implemented.

 Aerial view of our hemlock restoration planting field experiment.  Photo credit Rob Nelson.

Weather stations and pendant sensors used at our field sites being prepped for launch.

Take all of that planning and equipment to the field however...

A temperature/RH sensor hides in this radiation shield that was knocked over and wire severed.

 A sensor set-up measuring temperature/RH and soil moisture knocked over and pulled up.

 A weather station pulled completely out of the ground.

A repaired radiation shield stayed put, but the pendant sensor was bitten and cast aside.

A temperature/RH sensor that was pulled apart and chewed.

This damage had occurred over the course of several months and we had our suspicions as to who was responsible.  

Vandals!