Forest Health: A Small But Mighty Pest

The southern pine beetle (Dendroctonus frontalis) (SPB) is a small, seemingly innocuous beetle that brings new meaning to the phrase “small but mighty.” These beetles are known as the most destructive native forest insect in the Southeastern United States. While a single adult beetle is only about 1/8 inch long, the ability to aggregate quickly means these tiny insects can overtake a pine tree’s defenses in a short period of time. All species of southern pine are targets for SPB but favorite hosts include loblolly, shortleaf, Virginia and pitch pine.SPBpic1

Females emerge first in the spring and fly to a suitable host where they bore into the tree and start creating their infamous “S”-shaped galleries in preparation for laying eggs after mating. Shortly after, they emit a pheromone (think seductive bug perfume) and the masses begin flocking to the suitable host tree. Each female is prolific with her egg production, producing upwards of 150 eggs over the course of her life! These eggs are laid in the galleries where the developing larvae then feed on the inner bark. As trees are killed or fill up with beetles, the outbreak spreads to neighboring trees and continues until suitable host material is no longer found or control measures are taken.SPBpic2

Historically, outbreaks of these destructive insects have been cyclical, occurring on average every five to seven years. Since they are native, they have a predator complex which helps control the populations and regulate outbreaks. However, since the early 2000s these outbreaks have been less common and almost non-existent here in Virginia. Many factors may contribute to the decrease in southern pine beetle abundance, including more intensive silvicultural practices, genetically improved trees and forest fragmentation.

The last big southern pine beetle occurrence noted in Virginia was first detected in 2012, and had become a full outbreak by 2014. This took place on Chincoteague National Wildlife Refuge. The U.S. Forest Service observed the outbreak in 2016 from the air, and documented an average of 46 active SPB spots per thousand acres of host type. The average spot size calculated to be 1.5 acres. When a ground check was done, all spots visited had active adult, larvae and eggs, indicating that the population was still thriving. This area was hit particularly hard due to many factors: most of the pine was over-mature, overstocked and stressed from saltwater intrusion leading to a beetle buffet, ripe for the picking!

Unfortunately, no control efforts were enacted and the population continued to spread and the outbreak ultimately died out on its own. VDOF Forest Health staff flew the impacted area in October of 2018 and mapped 475 acres of pine mortality.

SPBpic3SPBpic4

To monitor populations and predict future beetle spots, each year VDOF Forest Health sets up traps that are baited with pheromones mimicking the ones produced by females and stressed trees throughout the state. Trapping starts in spring, around the time that beetles would start looking for suitable trees. Last year, we trapped in 10 counties, placing a total of 24 traps around the state. VDOF foresters and Virginia Department of Conservation & Recreation employees sample each week and VDOF Forest Health sorts the contents, counting the number of SPB caught as well as their associated natural predator, the clerid beetle. The good news for Virginia is that our SPB population levels continue to persist at low and static levels! We will continue to monitor these insects and their activity (or lack thereof!) and trapping efforts are planned for spring of 2019.

Field Notes: What’s in the Woods Today April 5, 2018

by VDOF Area Forester Lisa Deaton

Wildlife and Clearcuts Part 2

A beaver hut in the middle of a pond or swamp is a familiar sight.  The one above is located in Beaverdam Swamp in Gloucester County.

While mapping a creek for another Riparian Buffer Tax Credit application, I had the opportunity to see a number of signs of beaver activity alongside a clearcut.

beaver dam (1)

First, I came across the beaver dam above.  The beavers have built their dam in a breach of an old earthen dam.

beaver stump (1)

Then I walked by some recent beaver chewing activity.  Beavers do not eat the entire tree after they cut it down.  They consume the nutritious inner bark by chewing on twigs and branches similar to the way that people eat corn on the cob.  Note that this beaver left the pieces from the center of the tree on the ground instead of eating them.  While beavers might cut down very large trees, they are really trying to access the numerous smaller branches at the top of the tree.

beaver bites (1)

Can you imagine having jaws and teeth strong enough to bite pieces of wood this large from a tree?

beaver skid trail lo res (1)

What was most unusual was the beavers’ clever use of the adjoining 30-acre clearcut.  There were a number of paths on the edge of the beaver pond where beavers had traveled between the cutover and their pond to glean loblolly pine branches.  In the photo above, the yellow arrow follows the center of their trail to the water’s edge, and the pink arrow points out some pine branches that the beavers snacked on along the way.   This path was so heavily traveled that it looked like a smaller version of the skid trails in the cutover.

beaver water entrance (1)

At this water entrance (above), the beavers have chewed on the American beech tree on the left.  In the water, there are more twigs that have been stripped of all their bark.

Beavers have been harvesting trees for several million years in North America, while humans have walked the planet for about 200,000 years.  So perhaps it is fair to say that beavers have more logging experience than we do.  At this site, they were shrewd enough to benefit from human logging activity in their search for wintertime food.

pine branches

Field Notes: A Sure Sign of Spring!

by VDOF Senior Area Forester Scott Bachman

It is not quite spring, but the signs of spring are abundant at the New Kent Forestry Center.  The photo below shows one of the first signs of spring.

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The loblolly pine trees appear to have grown paper bags on their tips!  These contractors are placing bags on the trees to protect the soon-to-be receptive pine flowers (Strobli) from wind-blown pollen.  That brings up an obvious question, why?

These trees are destined to be used for control pollination seed production.  Control pollinated trees are some of the most highly desired tree seedlings that the VDOF produces.  They are desirable because the parentage of the seedlings is known.  These trees are like fine race horses, a flower from a fast growing tree is crossed with pollen from another fast growing tree.  The bags are essential to this process.

“In nature, loblolly pine trees typically are pollinated at random with the possibility of self-pollination, though rare, because of the way pollen and flowers are disposed on the tree,” explains VDOF Tree Improvement Forester, Onesphore Bitoki.

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“In general most of the flowers are in the top part of the tree crown while most of the pollen is at the bottom of the tree crown on the same tree.”

Loblolly pine trees in the forest are pollinated by the wind. Another sure sign of spring is finding your car covered in a fine yellow/green dust — loblolly pollen!  The tree improvement staff can use this to their advantage.  They can cover the flowers in a seed orchard tree with a bag and then inject pollen into the bag from a known fast-growing tree.  The resulting seed produced in the cone will have the high quality genetics of the two parent trees.

The covering of the branch tips is just the first step on a long process.  After the pollen season is over, the bags are removed from the tree and the cones marked.  Not all cones on a tree are “bagged” so each tip that was control pollinated must be tracked for 18 months before it is picked.  Pollinated cones will grow and develop seeds over the next two summers.  These high value cones, as well as our other orchard trees, are also managed to control insects that would like to eat the growing seed in the cones.

When the cones are finally mature they are harvested in Fall, typically in October, using high lifts or bucket trucks making sure the marked cones are kept separate from wind pollinated cones. Each cone is hand-picked and placed into marked containers identifying their “parents.”  This “name” will stay with each cone as it is dried and the seed removed, prepared for planting, planted, harvested at the nursery, packaged and ultimately sold to a landowner.  Like a fine race horse, this new fast growing pine stand can trace a pedigree back to these paper bags in the New Kent Forestry Center.

Field Notes: What’s in the Woods Today? March 6, 2018

Big Trees and Little Trees

by Area Forester Lisa Deaton

 

oak and house

Lately we have been recertifying trees for the Virginia Big Tree Register.  Trees on this register are checked every ten years to see if they are still alive, and if so, remeasured.  The swamp chestnut oak above is located in Mathews County.  It is 6.5 feet in diameter and 96 feet tall

We have also recently encountered a number of big trees that are not on the register yet.

Wezensky poplar

The yellow-poplar above (also called tulip poplar and tulip tree) is in the middle of a 40 year old pine forest, but within view of the owner’s house.

The same landowner has a tree that he and his granddaughter have named the Rest Stop Tree (below).

Rest Stop Tree

It is a yellow-poplar that fell over sideways early in its life, and the side branches started growing upwards.  The tree serves as a favorite rest stop during family walks.  Trees that are special for any reason can be nominated to the Remarkable Trees of Virginia Project.

Meanwhile, it is reforestation time, and very hardworking crews have arrived in Virginia to plant loblolly and shortleaf pine seedlings in cutovers.

planting crew

These men have traveled from Guatemala and Mexico to work in the southeastern U.S. for planting season.  Each man plants about 3,700 trees per day. lob-seedling.jpg

Field Notes: What’s in the Woods Today? Feb. 21, 2018

Owls and Berries

by Area Forester Lisa Deaton

Last week began with finding an owl pellet in my yard.  Lately I have been hearing the call of great horned owls.  In the past, we have seen barred owls and eastern screech-owls.

owl pellet

There are many good branches on the loblolly pine directly overhead for an owl to perch and digest a meal.

owl roost pine

I took a second look at the pellet after the rain, and the fur and bones could be from a squirrel.  The longest bones are 2 1/2 inches long.

wet owl pellet

Flocks of cedar waxwings have also been passing through.  When a whole flock feeds on the berries of an eastern redcedar or holly, it looks like the tree is waving all of its branches at you at once.

We found more berries while working with the Hampton Clean City Commission to plan a new “Central Park” in the City of Hampton.   The hackberry below was still holding fruit.  We did not study it closely enough to determine if it was a sugarberry, hackberry or dwarf hackberry.

hackberry berries

And, this greenbrier was heavily loaded with fruit.

saw greenbrier berries

We also noticed a slash pine with ripening male catkins that will produce pollen in the near future.

slash catkins

 

Field Notes: What’s in the Woods Today? Jan. 31, 2018

by Area Forester Lisa Deaton

Those Hidden Roots

Homeowners often contact our local Department of Forestry or Virginia Cooperative Extension offices when they are worried that a yard tree might be diseased or dying.

dying pine

This loblolly pine (above) is located on the shore of a tidal creek that flows into the Chesapeake Bay.  The needles and branches in the top of the tree have been dying for the past several months.  We initially thought that the harsh growing conditions of a saltwater shoreline and repeated flooding had finally taken its toll on this tree.  Then we found out that the tree’s roots had suffered through the construction of a home addition and the installation of a lawn irrigation system.  The homeowners thought that as long as the taproot directly under the tree was undisturbed then the tree would be fine.

While pine trees do have a central taproot, evident in the two tree stumps on the right, (below) they also have a large network of smaller roots and fine root hairs like the stump in the center of the photo.

roots 2

The fine roots of live trees are located in the first few feet of soil. Just driving over them with heavy equipment can compact the soil enough to damage those roots. Cutting through tree roots for irrigation systems or utilities (electric wire, cable, etc.) eliminates part of the original root system and creates wounds where diseases can enter the tree.
A general rule of thumb during home construction is to leave the ground underneath a tree undisturbed for at least the breadth of its canopy. A tree’s roots can extend away from the tree a distance of 1 to 3 times its height, which is a consideration for landscape planning, also.

These photos (below) provide a glimpse of the underground root system of hardwood trees.

roots 3roots 4

Here are a few more photos from an eroded shoreline on the York River  (Most of the fine root system of these dead pines has weathered, decayed and fallen off).

roots 5roots 6

Last, but not least, this is an interesting look at root competition.

roots on top of roots

The American beech tree in the upper left is crossing over roots of the sweetgum tree in the center, and another tree or vine’s roots are crossing over top of the root in the foreground.

 

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