Tuesday, January 29, 2013

Entomologist David Stephan to Retire

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

David Stephan writing among insect specimens. August 1973.
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.

smiling David Stephan at the microscope
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.

Tuesday, January 22, 2013

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

Tuesday, January 15, 2013

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.

Thursday, January 10, 2013

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.