Entomologist David Stephan to Retire

(Special thanks to Dr. Jack Bacheler, whose words formed the nucleus of this blog.) 

David Stephan, circa August 1973

After almost 40 years, David Stephan will step down from his position as the Entomology Specialist for the Plant Disease and Insect Clinic. Dave has been responsible for the identification of all insects, spiders, mites, and many other kinds of pests submitted to the Clinic by the public, extension agents, consultants, pest management companies, and researchers. Dave developed a reputation for being able to identify anything dead or alive that walks, digs, flies or swims. He was often called upon to identify the cause of arthropod plant damage even in the absence of physical remains of a pest.

Also a competent herpetologist, Dave additionally carried out a number of special identification and research projects with NCSU faculty, other scientists and students; worked closely with personnel from the NCSU Insect Museum; and was extensively involved with homeowner and agent training in the identification of insects and other arthropods. He was a regular presenter on satellite (later internet) training sessions broadcast several times a year to Cooperative Extension Agents and Master Gardener Volunteers.

David Stephan, April 2011

Dave's knowledge is not only broad, but deep. Beyond being able to identify many "critters", as he calls them, he also knows their life cycles and natural history. He has spent thousands of hours on the phone explaining insects and what they can and cannot do. We celebrate with Dave that he'll now have more time to spend in his beloved outdoors and doing the sorts of entomological taxonomy he enjoys, without the pressures of the clinic.

Beyond his formidable technical skills, Dave's diversity of interests and talents will be missed in the PDIC. Without Dave's black belt in the art of bad puns, the clinic will be a safer but duller place. He is a connoisseur of weather, of new words, of motion pictures, and of science fiction, particularly the Star Trek and Babylon 5 series. In spare moments we've chatted about everything from Broadway show tunes to the refractive index of diamonds. His is a mind that makes connections.

Last week, colleagues old and new joined to thank Dave for his many contributions to the Plant Disease and Insect Clinic, the Entomology Department, the North Carolina State University Extension Service and to the citizens of North Carolina. Since a replacement entomologist has not yet been hired, there will be a period of time during which insect identification services will not be available at the clinic. Please see the announcement on our home page for details.

Dave, don't forget: live long and prosper.

Is your heater hurting your tomato plants?

Tomato pollution damage (Photo: E. Lookabaugh)

Winter may have finally arrived, and with it, a serious issue for greenhouse growers. Over the past few weeks, the Plant Disease and Insect Clinic has received several tomato samples showing symptoms of pollution damage. The most common greenhouse pollutant is ethylene. Ethylene is an odorless, colorless gas which acts as a plant hormone. Ethylene is a growth regulator in plants, and excess ethylene is harmful to greenhouse crops. Tomatoes are particularly sensitive to ethylene and other pollutants like propane. Repeated exposure to very small amounts (0.01 ppm) over several days or exposure to higher amounts (1 ppm) for several hours can result in injury. 

Tomato pollution damage, twisted leaves (Photo: E. Lookabaugh)

The most common symptoms of ethylene exposure on tomatoes are epinasty (a downward bending of growth that causes plants to appear droopy even though they are not wilted), flower drop, and twisting of the upper leaves. 

Tomato pollution damage, pale leaf spots (Photo: E. Lookabaugh)

Tomato plants exposed to high levels of propane gas can have superficial stem lesions on one side of the plant (the side that faces the heating system) and leaves with tan to white lesions between the veins. Tomatoes will usually recover once they are no longer exposed to pollutants.

Tomato pollution damage, stem lesions, flower death/ drop (Photo: E. Lookabaugh)

Tomato pollution damage, superficial stem lesions (Photo: E. Lookabaugh)

Tomato pollution damage, stem lesions
and flower drop (Photo: E. Lookabaugh)

Faulty heating systems are usually the cause of pollution damage. The major causes of gaseous pollutants in a greenhouse system include dirty or improperly adjusted heating units, cracked heat exchangers, leaky gas lines, chronic use of unvented heaters, and exhaust from combustion engines. Pollutants can build up in the greenhouse when temperatures are borderline, causing heaters to kick on and off many times during the night. Exhaust from heaters that are not vented properly will lead to a build-up of incompletely combusted gases. Additionally, the any exhaust remaining in the exhaust pipe will flow back into the greenhouse. Alternatively, if nights are very cold and the heater runs a lot, insufficient oxygen feed can result in incomplete combustion and pollution damage.

Here are a couple of solutions to pollution issues in your greenhouse system.

1. Under cold conditions when ventilation systems are shut down, make sure the heater has access to a sufficient supply of oxygen. The grower may need to add an air intake source that feeds the heater.
2. Make sure pollutants are properly exhausted. If there is a crack in the heater or exhaust pipes, pollutants will remain in the greenhouse. There should be a small fan in the exhaust pipe that blows for about 20 seconds after the heater (and the heater fan) shuts off to be sure all pollutants exit the exhaust pipe. In a "vent-free" system, the first and last puffs of air should be exhausted because "vent free" heaters are 99% efficient except when they start and stop.

For more information on ethylene damage: click here 
For more information on faulty heaters: click here

Out of the Firewood and into the Parlor

Redheaded ash borer. Photo: Mike Wilder, NCCES

These striking photos were submitted to the PDIC as an online image sample. Several of these insects had been found crawling around furniture in a Rocky Mount, North Carolina residence. Our soon-to-retire entomologist Dave Stephan identified them as the redheaded ash borer, Neoclytus acuminatus, one of the most commonly reported of our "firewood beetles." Although it is called the redheaded ash borer, it can infest many different species of hardwood trees. Dave also provided the following information about this interesting situation.

Redheaded ash borer. Photo: Mike Wilder, NCCES

There are several species of longhorned beetles which can emerge from firewood in homes. Most of the species encountered this way in North Carolina belong to the genera Euderces, Megacyllene, Neoclytus and Phymatodes. Typically, females of these species lay their eggs in the bark of recently cut, storm damaged, or dying trees. The hatching larvae tunnel into the wood and complete their development in one year, although some species may take 2-3 years. Longhorned beetles in general spend their grub-like larval phase burrowing in wood, eventually pupating there. There is a certain chilling requirement for the insect to break diapause (hibernation). In simple terms, if the wood stays out in the cold long enough, the insect's body is primed for spring. When the wood is brought into the house, the warmth tricks the beetles into thinking that the winter has passed, and the adults emerge. Dave suspects that the insect is as surprised as the homeowner to find that it has emerged into a strange habitat. He says that the chance is "less than zero" that they will cause damage to wood products in the home, since they must lay eggs on a "green" tree with intact bark. They do not sting, transmit disease, or carry off children, but could bite (just a pinch) if handled roughly. To avoid the problem in the first place, burn firewood within two to three weeks of bringing it inside.

Firewood can be a means of moving more serious pests, too. See Rob Trickel's Guest Blog from November 5, 2012 for more information.

They're heeeere . . .

We've been enjoying some balmy days here in Raleigh, NC. So balmy, in fact, that our Japonica camellias are starting to bloom -- and when the blooms begin, petal blight cannot be far behind. A quick look under the camellias in front of Nelson Hall confirmed our fears. The tiny, mushroom-like apothecia of Ciborinia camelliae were popping out all over (below).

These tiny mushrooms bear the spores that infect the camellia blossoms. We generally miss the chance to spray for petal blight, but if you can catch it just as the apothecia emerge, you might be able to control it with fungicides. Later, the best control is to pick up all the spent and diseased blossoms as soon as they fall to the ground. This will reduce the number of apothecia that are produced the following spring.

For more information about petal blight, see our earlier blog post here.

For information about fungicides that control petal blight, see http://www.aces.edu/pubs/docs/A/ANR-0416/ANR-0416.pdf
Be sure to check with your local County Extension office to get the latest information about fungicide labels and use. Follow all label directions.

The Once and Future Chestnut

"Chestnuts roasting on an open fire…"

Dr. Larry Grand on chestnut. August 2004.
Photo: Caroline Vernia

I can count on the burned fingers of one hand the number of times I've eaten chestnuts, but for some of you they may be an important part of your holidays. A century ago – back the last time folks were dating their letters 12/21/12 – the American chestnut, Castanea dentata, was one of the most prominent trees of the eastern North American forest, from New England down the Appalachians and areas to the immediate west and south (range map). Apart from the prized wood, these trees provided nuts that served as food for humans and wildlife. There was a problem, though. From the area around New York City a blight was spreading. By the time Mel Tormé and Bob Wells had penned "The Christmas Song" in 1944, most of the native range of the American chestnut had been affected by the disease. Now most of the chestnuts are gone from their original range. The picture at left was taken in 2004 and shows retired NCSU forest pathologist Larry Grand standing on the remains of a once great chestnut tree (I don't actually know the cause of death in this case.)

Fruiting bodies of Cryphonectria parasitica
on the trunk of a chestnut tree. October 2006.
Photo: Marc Cubeta

So what happened? This was another case of an introduced fungus causing widespread destruction on a plant species that had not evolved resistance to it. See the discussion of coevolution in our Dec 3rd blog, if you missed it. The fungus Cryphonectria parasitica had been brought accidenetally from Asia on seeds or seedlings. This fungus causes branch and trunk cankers that eventually girdle and kill the tree. Of all the tree species susceptible to C. parasitica, the American chestnut is the most seriously affected. The fungus reproduces by spores formed in orange-colored fruiting bodies on the bark (picture at right). Two types of spores are produced: one that spreads by wind and one that is transported by birds, insects, or water splash. When spores reach a wound on a chestnut tree they germinate, and the fungus infects. According to information provided by the American Chestnut Foundation, it takes only 2 to 10 years for a mature chestnut tree to die. For more information on the disease process, see the March/April 2012 issue of the Journal of the American Chestnut Foundation. 

Unfortunately this sort of scenario has repeated itself with increasing frequency and rapidity as efficient transportation systems have allowed us to move plants and their diseases around the globe. In October 2011, the disease called "box blight" was first found in North America. Within months it had been found in nine US states and one Canadian province, and it hasn't stopped spreading. This has implications not only for the nursery industry, but for the cut greens industry this time of year. For more information about this threat specific to boxwood and Pachysandra, see Dr. Kelly Ivors' box blight information pages.

Chestnuts. Western NC. October 2006.
Photo: Marc Cubeta

Returning to the chestnut trees, it is an interesting fact that the roots are not killed by the fungus, so new sprouts can repeatedly develop. Eventually, though, this new growth succumbs to the blight. Back in October of 2006, one of our professors came across a chestnut tree in the North Carolina mountains that had grown large enough to bear nuts, though it was clearly infected with chestnut blight (picture at left). I suspect it is gone by now.

Concerted efforts to bring the chestnut back have been going on for some time. Different strategies have been attempted, the most important of which is to cross the native species with resistant species, principally Castanea mollissima, the Chinese chestnut. Another approach was to inoculate trees with a weak (“hypovirulent”) form of the fungus that prevented the deadlier version from killing them. The main reason these strains are weak? They themselves have a viral infection! The 2004 Annual Review of Phytopathology contains an analysis of this situation. (For those unfamiliar with the term, "phytopathology" is the study of plant diseases.) Sadly, one of the hurdles faced by growers trying to re-introduce the chestnut is yet another disease: root rot caused by the fungus-like organism Phytophthora cinnamomi.

Wishing a safe and enjoyable holiday season to all our readers from the NCSU Plant Disease and Insect Clinic! Note that we will be closed December 24th through January 1st, but looking forward to serving you in 2013.

Nematodes in the Tree Tops

Deodar cedar, NCSU Campus
Photo: M.J. Munster, PDIC

Japanese black pine, Wilmington, NC.
Photo: John Wooldridge, NCCES.

What do the two trees in the foreground of these images have in common? They are both infected with the pine wood nematode. This pest also goes by the name "pine wilt" nematode and by the jaw-breaking scientific name Bursaphelenchus xylophilus. That's a big name for roundworms less than a millimeter long. They also are narrow and nearly transparent, making them difficult to see without a microscope. The micrograph below shows swarms of them emerging from a bit of infected wood that was placed in water. Although they are called pine wood nematodes, they can invade a number of genera of conifers in addition to pines.

Bursaphelenchus xylophilus
Photo: NCDA&CS Nematode Assay Laboratory, Weimin Ye

Let me back up a moment for those not familiar with the Phylum Nematoda. Nematodes in general are extremely abundant on our planet, but relatively few cause economic damage. Most species are marine - ask your children if they've seen them on "Sponge Bob." Most of the terrestrial types are not parasites but are free-living scavengers and predators. A few bad actors besmirch the nematode name by causing human and animal diseases like trichinosis, hookworm, pinworm, and canine heartworm. Most plant parasitic nematodes live in roots and soil, such as the famous root-knot nematode (Meloidogyne species). Pine wilt nematodes are an exception. They don't inhabit the soil at any point in their life cycle and rely on a beetle to carry them around. The story is a bit complicated, but goes something like this…

Monochamus carolinensis,a species of pine sawyer
Natasha Wright, Florida Dept. of Ag. & Consumer Services
Bugwood.org

To get things started, you need a live or recently dead tree or log that is both loaded with pine wood nematodes and infested with one of the longhorn beetles known as pine sawyers. Inside the beetle galleries, the nematodes move into the trachea (breathing tubes) in the sides of the beetle. When the young adult beetles emerge from the wood, their first act is to do what's called a maturation feeding on the bark of healthy conifer twigs. Thus the beetle both carries the nematodes to a new tree and gives them an easy entrance by exposing the wood. There are no recorded instances of the nematodes ever saying "thank you" for this service. Once in the wood, the nematodes mature, reproduce, and colonize their new home. From there, disease progress can be slow or rapid. Tree growth slows down, and needles begin to yellow, wilt, and brown. This can happen on the whole tree or just one branch. Eventually the tree may die. Some of this information - plus the juicy details of the process, involving toxin production and "catastrophic xylem cavitation" - is found in Sinclair & Lyon's book Diseases of Trees and Shrubs, 2nd edition.

Austrian pine (background) and red pine, Wisconsin
USDA Forest Service – North Central Res. Station Archive
Bugwood.org

The astute reader may have noticed something else about the trees pictured above: they aren't native to North America. This is not a coincidence. Although our native pines can become infested by pine wood nematode, most species are not seriously harmed unless they are also under drought stress. The photo at left shows healthy native red pines and pine-wilt-affected Austrian pines in Wisconsin. The native conifers, the pine sawyers, and the nematodes all "grew up together", so to speak. There's been a millennial struggle for the upper hand that's led to a sort of stalemate over the years. Any trees that were too susceptible to the nematodes have died out. Likewise any nematode that could not prosper in the trees didn't survive. We call this process "co-evolution". Newly imported nonnative hosts suffer greatly in this situation, because they never evolved defenses against the local pests. Japanese black pine is a wonderful tree for our coast because of its salt tolerance, but many are lost to pine wilt nematode. Even worse is the situation in Japan and some other parts of Asia. There native pines have been devastated following the introduction of Bursaphelenchus xylophilus.

Sample of Japanese black pine as
received at the NCSU PDIC

If you have a tree that you believe might have pine wilt nematode, contact your County Cooperative Extension Service about sending a sample to the PDIC. Unfortunately, the best sample is rather destructive: a six-inch-long segment of the main stem (2-4" diam), just below the dead terminal. The picture at left shows an excellent sample we received earlier this year. We will forward the material to the NCDA&CS Nematode Assay laboratory. There is no cure for infected trees. The actions you take will be to prevent problems for healthy trees down the road, both literally and figuratively. Trees that test positive should be removed and destroyed. To prevent existing or new beetle infestations from moving the nematodes around, promptly chip the tree. After doing some investigating into the biology of the beetles, our Dr. Chuck Hodges has added the recommendation: "If feasible, it may also help to remove the stump 2-3 inches below ground line." In some quarters the idea seems to have circulated that stumps should be treated with borax. This is actually a practice used to combat annosum root rot - another occasional killer of conifers - but that will do no good against pine wilt. Much more information about pine wilt disease can be found in US Forest Service Publication NA-FR-01-04.

Fungal frustrations

I've been wanting to write about this situation for quite a while, but only now have found the time: nuisance fungi in landscape beds. I'm going to zero-in on the two most aggravating groups: the stinkhorns and the artillery fungus. Other nuisances include the bird's nest fungi and certain true mushrooms. The "dog-vomit slime mold" is a very different sort of organism and was covered in our June 2011 blog post.

Stinkhorns. Wake Co., NC. Oct 2012. Photo: Greg Florian

Most stinkhorns are very conspicuous horn-shaped fungal fruiting bodies several inches tall that produce strong odors, unpleasant to humans. It's a bit hard to write about the stinkhorns without losing our PG rating, so I'll leave it to you, the reader, to look up the meanings of some of the Latin names if you want to know more. We received the image at left from a homeowner in Wake County. These are almost surely Phallus ravenelii, and they appeared in his mulched bed in early October. The submitter said he could smell them from two houses away. Is there a purpose to this odor, you ask? Take a close look at the picture and you can see that flies have been attracted to the stinkhorns. Why, you wonder? Well, the sticky green portion at the top contains the spores of the fungus. When flies visit, they pick up some of the spores and carry them away to new locations, so they're a means of dispersal for the fungus. You may have heard of a similar raison d'être for the foul smell of skunk cabbage, though in that case it's to attract pollinators. Fortunately for farmers and home gardeners alike, the odor does not persist once the fungi are gone.

Clathrus columnatus. Wake Co., NC. Jan 2008

Over several weeks in October and up until about our first frost, there were large numbers of stinkhorns in a the landscaped median of a major road near campus. Traffic didn't allow me to get a good look, but I think they were Mutinus elegans. This genus has a more tapered apex than Phallus. Back on January 18, 2008 I found a specimen of Clathrus columnatus on a south-facing slope here on the NCSU Campus. It had the smell of spoiled fish wrapped in a wet diaper. The fruiting body of this species has four "arms" fused at the apex.

Sphaerobolus gleba on siding. Jackson Co., NC.
Oct 2010. Photo: Christy Bredenkamp

Sphaerobolus gleba on gardenia leaf. Wake Co., NC. Oct 2012.

A very different dispersal mechanism is used by fungi in the genus Sphaerobolus. Their fruiting bodies on the mulch are small and inconspicuous, but they launch tiny dark spore balls for distances up to several feet, earning them the name "artillery fungus" or "cannonball fungus". The spore masses, known as gleba, stick fast to whatever they hit: plants, siding, and vehicles. Even when scraped off, they leave a stain, causing great frustration for the owners of affected homes and cars.

There's a lot more to these fungi than meets either the eye or nose. Their real "body" consists of a network of fine threads called hyphae that grow throughout the soil and mulch, where they decompose dead organic matter such as the mulch itself. The good news is that they do no harm to trees, shrubs, or bedding plants. The bad news is that there's no easy way to get rid of them. There are certainly no fungicides or disinfectants you can use in these situations. Removing stinkhorns as soon as they appear will help with the odor problem. Turning under the existing mulch and replacing it with composted mulch or a coarse pine bark mulch may help. Dr. Harry Hoitink of the Ohio State University has a very interesting fact sheet that includes a discussion of the microbial ecology of composts. One of his conclusions: "… water applied at the right time during composting, storage, and mulching can solve most of the fungal nuisance problems." Another very informative resource comes from Dr. Donald Davis at Penn State University. His Artillery Fungus FAQ gives details about this organism, how to deal with it, and suggestions from readers about how to remove the spots. It appears from reading his page that Dr. Davis has dealt with everyone from homeowners to attorneys about this issue.

Most fungi outdoors in North Carolina are going to be hidden from view over the winter, but keep the nuisance fungi in mind when planning your next landscaping project. You may be the next one to notice an unusual smell in the neighborhood.

Don’t Move Firewood!

Photo: Larry Grand

With a chill in the air and leaves turning brilliant colors here in Raleigh, our thoughts turn to cozy firesides, big bonfires, and warm campfires after a long day’s hike. With this in mind, we asked Rob Trickel of the North Carolina Forest Service for a timely reminder about the dangers of moving firewood. 

Invasive Pests and Firewood Movement

Non-native invasive forest pathogens and insect species have potential to cause great harm to North Carolina’s forests and landscapes.  The fungus that causes laurel wilt is killing redbays and swampbays in the Coastal Plain and we think it may also devastate sassafras across the state.  Other invasive diseases and insects that have the potential to cause great harm to walnuts (thousand cankers disease), ash (emerald ash borer), and a variety of hardwoods (gypsy moth) are found in counties in Tennessee and Virginia adjacent to our state (see current invasive monitoring map).  In addition, Asian longhorn beetle is devastating a wide variety of hardwood tree species in the Northeast and Midwest, and has the potential to do the same here.   All of these pests have the following in common:  they move naturally from place to place at a very slow rate, but can be spread rapidly if moved in firewood.

Emerald Ash Borer Galleries in firewood. Photo: Troy Kimoto, Canadian Food Inspection Agency

Moving firewood can introduce invasive pests to new ecosystems, where they can cause ecological, economical, and social problems in our forests.  In response to the rapid spread of emerald ash borer via firewood, some states have even enacted laws regulating the movement of firewood to slow the spread of invasive species.  North Carolina is approaching the problem with public awareness and education campaigns and has joined with other southeastern states to promote the use of local firewood or firewood that has been treated or certified to be pest-free.  

As part of the effort, the Changing Roles program of the USDA-Forest Service has developed two fact sheets about firewood movement as a means of spreading invasive species to new areas. These fact sheets help equip our partners who work with various audiences (consumers and producers of firewood) with information to combat the spread of invasive pests.

Fact Sheet 5.4 (Invasive Species and Firewood Movement) is firewood/invasive species 101 and covers:  What is firewood?  What types of invasive pests are transported in firewood? Why is the movement of firewood a pathway for the spread of invasive pests? What are the ecological, economical and social effects of invasive pests?  

Fact Sheet 5.5 (Preventing Firewood Movement) concentrates on how to engage a variety of audiences on firewood issues including:  How do we (foresters, extension staff, natural resource professionals) communicate with and engage different audiences on this important topic? How do we work with homeowners and outdoor enthusiasts (also parks and campground staff, arborists and green industry professionals, wood processors and producers) to combat the spread of invasive pests?  How is the movement of firewood regulated? And, where can I find more information about preventing firewood movement?

You can find more information about firewood movement and forest health, excellent images of the insects and diseases that can be spread by moving firewood, some very entertaining videos at www.dontmovefirewood.org   

Photo: Rob Trickel

 

Prepared by Rob Trickel, Forest Health Branch Head, North Carolina Forest Service