Field Notes: Milkweed Magic

By Ellen Powell, VDOF Conservation Education Coordinator

For a plant with ‘weed’ in its title, milkweed is a pretty awesome plant. It contains toxins called cardiac glyphosides, which deter feeding by most insects and mammals. Despite this trait, a milkweed plant is a little universe unto itself. In fact, one study documented more than 450 species of insects visiting milkweed in a single midwestern field.

You probably already know about the association between milkweeds and monarchs (Danaus plexippus). The caterpillars of these iconic butterflies feed only on plants in the milkweed genus, Asclepius. As a reward for this boring diet, their bodies retain the toxins produced by the plant. These persist into adulthood, making adult monarchs distasteful to most predators. The butterfly’s black and orange coloring and the caterpillar’s contrasting stripes are nature’s warning to stay away.  

Monarch cats!

But monarchs aren’t the only milkweed lovers in the insect world. Currently, the only milkweed in my garden is a single large specimen of swamp milkweed, Asclepius incarnata. In June, its pink blooms were abuzz and aflutter with many different insects. (The nectar isn’t toxic and attracts all sorts of nectar feeders.) After the blooms faded, I ignored my plant for a month or two. When I examined it in September, I found, in addition to seven hungry monarch caterpillars, a few other interesting insects that feed on milkweed.

Bumblebee on milkweed

Large milkweed bugs (Oncopeltus fasciatus) are “true bugs” of the order Hemiptera. They feed mainly on milkweed seeds, probing through the pods with their long piercing mouthparts to suck juices from the seeds within. Like monarchs, milkweed bugs accumulate toxins in their bodies, and like them, they sport a bold color pattern. This is an example of Müllerian mimicry, in which two or more species look alike and are both noxious to predators.

Large milkweed bug

Milkweed leaf beetles (Labidomera clivicollis) look a bit like very large, chunky ladybugs. Both their larvae and adults feed on milkweed leaves. Unlike monarchs and milkweed bugs, these beetles do not build up toxins from the plants, but they do share the same contrasting colors. This is an example of Batesian mimicry, in which a tasty species mimics one that tastes bad.

Milkweed leaf beetle and aphids

My milkweed also attracted yellow aphids this year, seen in the background of the beetle photo. These are most likely oleander aphids (Aphis nerii), an introduced pest that feeds on (you guessed it) oleander in its native Mediterranean habitat.

Fourteen species of milkweed are native to Virginia. Clusters of white, pink, purple, or orange flowers bloom from late spring through late summer, depending on species. In late summer to fall, the seed pods will split to release fluffy seeds that drift away in the wind.

Many Virginia gardeners cultivate milkweeds for their flowers and for their benefit to monarchs. The summer generations of monarchs live only a few weeks, but September’s caterpillars are different. They will transform into the tough, yet lovely, butterflies that will make a 3,000-mile journey to central Mexico, hang out for the winter, and return to the U.S. in spring.

My monarch caterpillars all left the plant to pupate when I was away for a few days. I looked everywhere for their chrysalises, but in my jungle of a garden, I couldn’t find any. Hopefully they’ll all produce strong, healthy monarchs capable of making that long flight.

Monarchs are a species in trouble. Contributing factors include habitat loss on both breeding and overwintering grounds, climate change, and pesticide use. You can help by growing milkweed in your own yard. (Buying plants from a nursery is usually the best option, because milkweed seeds don’t germinate reliably.) When friends ask what that interesting plant is, don’t be afraid to tell them it’s a weed – and a very cool one!

Field Notes: What’s in the Woods? Best of Summer 2019

By Area Forester Lisa Deaton

A Round-up of Interesting Moments & Encounters in the Woods from Summer 2019

When a local deadline for forest land use reports passed in late fall, I had time to share photos from the past few months. Note:  Land Use Assessment is available in many Virginia counties (but not all) for property owners with 20 or more acres of woods.  You can check with your local Commissioner of the Revenue to see if it is an option for your property.

 

MUSHROOMS EATING BUGS

lichenhopper 1

While walking with a landowner through a 23-year old loblolly pine stand to see if the stand could be commercially thinned, we encountered this grasshopper “shell” which appeared to be growing lichens.  Our forest health staff explained that this grasshopper died from an entomopathogenic fungus, sometimes referred to as zombie fungi.  A fungal spore infected this grasshopper, then consumed its body to grow a new fruiting body to release more spores.  So, what appeared to be lichen is actually the “mushroom” formed by the fungus.  The many species of “zombie” fungi are host specific, and serve as a natural control for many insect populations, such as our invasive gypsy moth.


BUGS EATING BUGS

IMG_3791 histerid ZOOMWhen we experience hot, drought-y periods, pine bark beetles can kill their host pine trees by girdling the trees with their tunnels.  The lack of soil moisture prevents the pines from being able to drown out the invading insects with tree sap.  While trying to identify which type of beetle had killed a yard tree in Middlesex County, we found a histeridae beetle (genus Platysoma) that was infested with mites.  Keep in mind that the total length of the host beetle in the microscope photograph above is 2 mm.  Platysoma beetles are predators that eat ips beetles, so while we did not find an ips beetle, it is a sign that an ips species helped kill this particular loblolly pine tree.

BUGS EATING ME

It is common in July and August for foresters to leave the woods covered with “seed” ticks, or clusters of the larval stage of various tick species that are as small as seeds. Each of the tiny dots on the pant leg in this photois a tick larva.

seed ticks

I am always glad to say “¡Hasta la vista!” to them at the end of the summer.  There is much more to the tick story but I will save it for next summer.

WILDFLOWERS 

possumhaw

 

 

While the ticks are no fun, seeing wildflowers and shrubs in their natural setting is one of the joys of working in the woods.  This shrub is Viburnum nudum, also called possumhaw.  The berries start out pink and turn deep blue, and are eaten by songbirds, wild turkey, and squirrels.

 

 

 

FLYING SAUCER HITS A TREE

flying saucer in woods

 

Summertime in Virginia provides the heat and moisture needed by all sorts of fungi in order to flourish. This appears to be a type of shelf fungi, possibly Oxyporus populinus. The mushrooms in the photo below had a fairy tale look on a particularly sweaty day.  A local expert identifies them as silky rosegill.

hollow tree mushrooms ZOOM


LOVING THE HEAT?

buzzards
While many mushrooms thrive in the heat, these black vultures gathered around a sunken bathtub on an 80-degree morning.  After weeks of 90-degree temperatures, they were not bashful about seeking relief from the heat near a house.


QUAIL ATTACK

While preparing for a talk on Forests and Climate Change, I ventured out to photograph a clearcut (below) on the water’s edge that has grown back in an invasive species, phragmites, or common reed.

phragmites

I was surprised to encounter a covey of bobwhite quail in such dense vegetation.  According to the landowner, quail have inhabited this tidal area for several years.  I heard the young quail peeping in the reeds, then two adult quail leapt into the road — one acted like it had a broken wing for several seconds (a defensive mechanism meant to distract predators away from their more vulnerable young), then both adults charged towards me.

Field Notes: What’s In The Woods Today? September 2, 2019

By Project Learning Tree Coordinator Page Hutchinson

Look A Little Closer…

Although I work for the Virginia Department of Forestry, my job doesn’t actually allow me much time in the forest. Being a tree hugger from way back, I take as many opportunities as I can to get in the forest. On the recent Labor Day holiday, my friend Karen and I went for a hike on the Graves Mill Trail in Madison County. This easy trail follows along the Rapidan River and allows you to enjoy both the water and the forest. I use the term “hike” loosely. Karen and I call these our pokes as in we poke along examining this and that and enjoying all that we see. Very rarely is there an actual destination. Our day is driven by when we need to turn around and get back before dark. I don’t know that we’ve ever even tracked actual distance.

On this particular poke, we arrived both of us feeling stressed and somewhat harried from life and work events over the past few weeks. We quickly found a boulder on the water’s edge just to soak in the soothing sound of the moving water. Once restored, we headed on down the trail to see what we could see. Most noticeable were the splash of wildflowers, the profusion of ferns and the dance of many butterflies. Butterflies are hard to identify unless you can get a really good picture of them. That’s certainly easier said than done!

Beyond the most noticeable, we like to focus on the lesser-noticed beauty the forest has to offer: small fungi poking through the leaf litter, lacy patterns on leaves created by insects, unique shapes of tree trunks, designs and colors on rocks, and even the fabulous design of decomposing bark. Our most amazing discovery that day was some sort of insect case made out of folded fern leaflets. We found several and dissected one, but didn’t find anyone home.

We even enjoyed a refreshing dip in the river. A great poke, and a great day all the way around.

Field Notes: What’s In The Woods Today? August 14, 2019

By Area Forester Lisa Deaton

Dung Beetles

A local farmer asked me to examine a 40-year-old stand of loblolly pines to see if they were large enough to harvest. A corn field was located in the center of the property and we noticed some very fresh deer scat along the field edge. On the way back to the truck we saw something moving on the ground. It was a dung beetle, who had also noticed the fresh deer scat. I tend to forget that we have dung beetles in Virginia, but indeed they are found worldwide:  https://kids.nationalgeographic.com/animals/invertebrates/insects/dung-beetle/

Notice that the beetle uses its hind legs to roll the dung ball:

National Geographic also has a video of an epic battle over a dung ball:

https://www.nationalgeographic.com/animals/2019/01/beetles-fight-over-dung-ball/

Field Notes: Yellow-Poplar Weevil Makes Presence Known in Southwest Virginia

by VDOF Forest Health Program Manager Lori Chamberlin

The yellow-poplar weevil has made its presence known again in southwest Virginia. This native insect generally causes very little damage, but the population increased enough this summer to have a noticeable impact on yellow-poplars in the southwest part of the state. The weevils are black and small, only about 1/8th of an inch long. Since this pest is a weevil, it has a long proboscis, or nose like appendage, that it uses to feed. Though their name implies they feed only on yellow-poplar, they also feed on magnolia and sassafras.

Adult yellow-poplar weevils emerge in early June and feed on leaves until mid-summer. As they feed, they make tiny notches shaped like a grain of rice in the leaf creating brown splotches on the leaf surface. This gives the trees a scorched appearance and may lead to premature leaf drop.

Since the yellow-poplar weevil is a native pest in the eastern United States, control is usually not warranted. Natural predators of the weevil normally regulate the population and keep it below damaging levels. Outbreaks of the weevil tend to occur every few years when weevil populations surpass natural predators. During outbreak years, tree damage may be unsightly and alarming, but is mostly just cosmetic and does not cause long-term harm to the trees. There have been six VDOF documented outbreaks in the last 25 years, all primarily in southwest Virginia. This year, reports of this pest came from Roanoke, Bedford, Buchanan and Russell counties. VDOF forest health staff conducted an aerial survey on July 2nd and mapped damage in Bedford, Botetourt, Roanoke, Montgomery and Floyd counties. Yellow-poplar weevil damage appears to be widespread throughout the western region this year, but it is patchy and scattered throughout the landscape.

In heavily infested areas, you may see these weevils crawling on top of vehicles or falling on people walking by. They are often mistaken for ticks, but don’t worry, the yellow-poplar weevil doesn’t harm humans!

IMG_3312

Centipede-shaped Galleries, Made by a Beetle!

The southern pine beetle typically gets all the attention, but there are other native bark beetles in our forests that often go unnoticed. One such beetle is the hickory bark beetle, Scolytus quadrispinosus.

HickoryBarkBeetle
Photo: Natasha Wright, Cook’s Pest Control, Bugwood.org

Adults are black, stout, and small – about 1/5 inch long. They fly to the tops of trees and feed on terminal growth, and then bore into the bark of trunks and branches to lay eggs. Females construct vertical egg galleries underneath the bark and deposit eggs  in small niches along either side of the gallery. When the eggs hatch, the larvae mine outwards, away from the main gallery, creating an engraving that resembles a centipede! This peculiar centipede-shaped design is easy to identify and a good indicator of a hickory bark beetle infestation.

The hickory bark beetle prefers hickory trees, although pecan and butternut are also listed as possible hosts. Beetles damage trees by creating galleries underneath the bark that may eventually girdle the tree. Foliage of infested trees will turn yellow, red, and finally brown as the tree succumbs. But not all hickories will die! The hickory bark beetle tends to only attack trees that are already stressed due to drought, fire, storm damage or disease. So keep your trees healthy with good cultural practices, such as thinning and irrigation, and you may never see signs of the hickory bark beetle.

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.

Forest Health: A Winter Pest Survey

Each month, Field Notes will bring you news from our forest health team. We kick off 2019 with a focus on winter activities and the hemlock wooly adelgid.

What do forest entomologists do in the winter? We look for hemlock woolly adelgid! The Forest Health program staff at VDOF surveys for many forest pests throughout the year, but the hemlock woolly adelgid is unique in that it is most active and visible during late fall and winter months. This invasive insect has been killing hemlock trees in eastern North America since its introduction into the United States in the 1950s. The tiny adelgid insects crawl along hemlock branches in search of a suitable feeding site, and settle at the base of needles where they insert their piercing sucking mouthparts into the plant tissue. They feed on the tree’s nutrients and produce a white ovisac, or covering, around their body for protection. If you ever see small white “cotton balls” on your hemlock tree, you probably have hemlock woolly adelgid.

hemlockwao
Hemlock woolly adelgid ovisacs on eastern hemlock

Most hemlock trees in Virginia are found in the western region, but there is an isolated population of hemlock situated east of the species’ major range at James River State Park in Buckingham County. In December 2018, VDOF visited this stand to assess the health of the hemlock trees and monitor the hemlock woolly adelgid population. While many hemlocks near the river still look healthy, there has been significant decline of hemlock trees further upland. Overall stand health was rated “fair” in comparison to the “good” rating just two years ago. Surprisingly, however, hemlock woolly adeglid populations appear quite low. The winter of 2017/2018 saw some extremely low temperatures which may have reduced adelgid populations. Bad news for adelgids, but good news for hemlocks.

mooneyham
Katlin Mooneyham, VDOF Forest Health Specialist, beat sheet sampling for L. nigrinus beetles

What kills adelgids beside cold weather? Beetles! Small predator beetles have been released as biological control of the hemlock woolly adelgid on federal and state lands throughout Virginia by various universities and federal agencies over the past decade. In 2005, Laricobius nigrinus beetles were released at James River State Park to control the hemlock woolly adelgid and hopefully preserve the population of hemlocks within the park. L. nigrinus is native to pacific northwestern North America and has been thoroughly screened and tested to ensure it is not a threat to non-target species. Since the release, the stand has been monitored to assess the population change of the beetles and the adelgid over time. The presence of L. nigrinus is determined by beat sheet sampling- a fun technique in which you shake a branch over a large white sheet attached to a cross frame and then identify all the beetles than fall from the branch onto the sheet. This sampling is done on dozens of hemlock trees and typically lasts about an hour. L. nigrinus beetles are very small and difficult to detect, but we found 6 adult beetles during our visit in December. These six beetles indicate the population of L. nigrinus is surviving and feeding on hemlock woolly adelgid which gives us a glimmer of hope for our hemlock trees.

Field Notes: Be Thankful for the Good Bugs!

by Forest Health Specialist Katlin Mooneyham

Here in the forest health program at VDOF, we spend a lot of time talking about bad bugs and how to kill them. Much of our time working with landowners and other forestry professionals is spent identifying pests, giving management recommendations and, in some cases, even treating trees against a variety of problematic insects. The emerald ash borer, an insect that originates in Asia, received a lot of our attention this year. Gypsy moth, a pest from Europe, typically makes an appearance each year in early spring and caused moderate damage in 2018. We also can’t forget our newest invasive insect, the spotted lanternfly! This pest showed up in the state in January of 2018 and has been the source of much attention and control efforts ever since. Sometimes it is exhausting trying to keep up with these invaders as they make themselves at home in our forests!

Given it is the holiday season, a time to be thankful for all that we have, I want to shift focus off these nuisance species, and celebrate the good bugs. They don’t often get the credit they deserve, even though they are constantly working hard in the background controlling the “bad bugs”. When these “good bugs” (also called natural enemies) control populations of pest insects, this is called population regulation.  This phenomenon involves a fluctuation of populations that cycle between the high population of an insect pest and the subsequent increase of natural enemy populations. Eventually the natural enemy controls the pest below injury level and to a point where the pest population is less than that of the natural enemy population. In natural systems where both species are native, these population dynamics fluctuate back and forth and remain in balance so long as the ecosystem is not altered (Stevens 2010) (see figure 1).

Figure 1:Nov20

Insects that act as natural control agents can fall in to two different categories- predators and parasitoids, though natural control also encompasses fungi, bacterial and viral pathogens of invertebrates. Predators are insects that rely on their prey as a food source. Sometimes only a certain life stage of an insect is predacious; the larvae may be predators while the adult stage feeds on nectar. Other species are predacious their whole lives, controlling pests constantly! Parasitoids are awesome insects that don’t harm humans, but parasitize other insects when they are young and then are free living as adults. They can parasitize and use their hosts for food or can use them exclusively for homes while they develop! Either way, they ultimately kill the host they rely on. Take away message here- Mother Nature is awesome and clearly there is a lot in the natural world to be thankful for!

One of our favorite native predators here in Virginia is the checkered clerid beetle, Thanasimus dubius (Figure 2). This species is a native predator of the southern pine beetle (SPB), the most destructive native insect in the southeastern U.S. Both the adult and larval stages of this predator feed on all life stages of southern pine beetle, as well as many other native pine beetle species in Virginia. In the VDOF forest health program, we trap annually for SPB and clerid beetles and use the number of clerid beetles as an indicator of SPB population status. If we catch more clerid beetles than SPB, as we have the past few years, we know that the SPB population is at low and static levels and the predators are controlling the SPB.

Figure 2:

cleridbeetle
Credit: Gerald J. Lenhard, Louisiana State University, Bugwood.org 

An amazing native parasitoid found in the woods of Virginia is Megarhyssa nortoni, a lovely wasp that looks terrifying but is actually specially adapted to find larvae of a horntail grub underneath bark (Figure 3). She probes the wood trying to catch the scent of the fungi that horntail cultivate. Once she finds a suitable spot, she drills into the tree laying an egg on or near the horntail grub. Once her egg hatches, it consumes the entirety of the horntail grub, killing it.

Figure 3:

wasp
Credit: Steven Katovich, USDA Forest Service, Bugwood.org 

These two examples represent only a very small portion of the natural control going on in our forests around us. All of our native pests are controlled by natural agents that keep the pests from reaching destructive levels for too long. Non-native pests can be so damaging in the U.S. because they arrive without natural predators to keep them under control and they are effectively at a buffet in our forests and ecosystems. So let us toast our good bugs this holiday season and be grateful for all they do in our forests around us!

Happy Holidays from the VDOF Forest Health Program!

Literature Cited:  Stevens, A. (2010) Dynamics of Predation. Nature Education Knowledge 3(10):46