What will happen to the OJ? A virus is destroying citrus plants in Florida

by Emily Hayes, Sustainable Plant Systems major

In the past several years, a virus infecting citrus crops has become increasingly hazardous to food security and plant health in the United States. The virus has largely impacted other countries previously, but did not spread to the US until recently. According to Bar-Joseph et al. it is a very difficult virus to manage.

The virus is known as the tristeza virus (CTV) and is vectored by aphids. It has been the cause of millions of citrus trees to decline in health and die and is one of the most significant citrus diseases in recent years. It appears to be mostly a problem exacerbated by man because of the introduction of new varieties into citrus fields (and use of sour orange rootstock in cultivation). The virus is not transmitted by seeds but can be spread by infected trees (grafts) shipped from Asia. Like most viral plant diseases, infected plants can be asymptomatic or produce symptoms of other plant health problems.

Florida grown citrus plants have taken a huge hit from CTV. Because of Florida’s climate, oranges tend to grow juicier compared to climates like California and thus a significant portion of orange juice production is in Florida. CTV has impacted the citrus growing industry greatly in Florida and other parts of the world. The types of citrus most susceptible to the decline strain are sweet oranges grown on a sour-orange rootstock. The virus is so devastating because it can cause stem splitting in citrus trees that are not grafted on sour-orange rootstock. It spreads very rapidly and the introduction of a certain species of aphid in the mid 90’s was the start of the epidemic that is now affecting the citrus production in Florida.


M. Bar-Joseph, R. Marcus, R. Lee. 1989.  The Continuous Challenge of Citrus Tristeza Virus Control. Annual Review of Phytopathology 27: 291-316


My name is Emily Hayes. I am a senior at The Ohio State University majoring in Sustainable Plant Systems with a specialty in Horticulture and minoring in Soil Science. I currently work at The Chadwick Arboretum, located on OSU’s campus.

High Elevation Science

by Bethany Kyre, Plant Pathology major

Mountain Pine beetle, Dendroctonus ponderosae, is a species of bark beetle. They feed on the inner bark of ponderosa, lodgepole, limber, and scotch pines of the western United States. MPB prefer older, stressed trees because, as a defense, healthy trees produce resins that can physically push the beetle back out of the tunnel they have burrowed and encase them in a sticky tomb. The more stressed a tree is, the less resin it produces. MPB is responsible for the death of great swaths of forest throughout the Rockies.

Upon maturity, an adult beetle will emerge from a tree and fly to another, guided by the scent of terpenes. Older trees produce a different scent than younger trees, allowing the beetle to differentiate between the two.  Once a female beetle has found an appropriate tree and a mate, she will dig out a gallery and lay her eggs. Once the eggs are laid, the adult beetles will die. MPB have a complete lifecycle, meaning they hatch from their eggs, grow into larva (the overwintering stage), pupate, and then emerge as adults to begin the cycle again.

One very interesting part of the story takes in the high elevation forests of above Nevada, outside of Great Basin National Park. In these 10,000+ ft tree stands, scientists from the Rocky Mountain Research Center in Utah have noticed that not a single bristlecone pine has been killed by the MPB, despite growing in mixed stands with limber pines. Bristlecone pines are among some of the oldest living organisms in the world – some have been aged at 5,000 years old! It could be that bristlecone pines encountered the beetle thousands of years ago and have since evolved MPB specific defenses.


Colorado State Forest Service > Mountain Pine Beetle

Bentz BJ, Hood SM, Hansen EM, Vandygriff JC, Mock KE. 2017. Defense traits in the long-lived Great Basin bristlecone pine and resistance to the native herbivore mountain pine beetle. New Phytol. 213(2):611-624.

This blog post was an assignment for Societal Issues: Pesticides, Alternatives and the Environment (PLNTPTH 4597). The views expressed are those of the author and do not necessarily reflect the views of the class, Department of Plant Pathology or the instructor.

“Transgenic American chestnuts could soon take root” (theconversation.com)

by Jonathan LaBorde, Sustainable Plant Systems major

chestnut blight

Chestnut blight canker. Williams Powell CC BY-ND. From The Conversation (source cited below)

This article is regarding the American Chestnut tree and its path to overcome the exotic pest fungus that has historically decimated its populations.

Anyone who has grown up in the American hardwood and Appalacchian areas knows that the American chestnut used to be an important hardwood timber tree. The total number of American chestnut trees was estimated at over three billion with 25% of the trees in the Appalachian Mountains being American chestnut. This was of course before the chestnut blight was introduced to the United States.

Chestnut blight is caused by the Asian bark fungus Cryphonectria parasitica. It was accidentally introduced to North America on imported Asiatic chestnut trees. Since the Chinese chestnut trees have evolved alongside of this pathogen they are not susceptible though the American trees were highly susceptible.

The airborne fungus spread 80 km a year and in a few decades killed up to 3 billion American chestnut trees. This reduced population was scattered among Appalachia and many were saddened by the loss of their beloved chestnut forests. Trails and parks have been named after this iconic American hardwood such as ‘yellow mountain’ and’ yellow gap’ that are named when in fall the whole mountain would be turned golden from the changing colors of the chestnut’s leaves.

Just as soon as it might be an end to true chestnut trees in the U.S., technological breakthroughs are bringing them back. A new transgenic breed of American chestnut is resistant to the fungus and aims to help restore these forest giants to their home. A group at SUNY College of Environmental Science and Forestryhas successfully created a transgenic hybrid of these trees and is beginning to plant them in the forest. There is still a lot of work that needs to be done to restore the forest ecology but with advances like this, the future for the Appalachian forest seems promising.


Blog post written by Jonathan LaBorde at The Ohio State University, Bachelors of Science in Agriculture – Major Horticulture.


The Conversation > New genetically engineered American chestnut will help restore the decimated, iconic tree

This blog post was an assignment for Societal Issues: Pesticides, Alternatives and the Environment (PLNTPTH 4597). The views expressed are those of the author and do not necessarily reflect the views of the class, Department of Plant Pathology or the instructor.




The Death of Ohio’s Shade

Symptoms of Dutch elm disease. Photo: Richard Webb, Bugwood.org

By Daniel Zellars, Sustainable Plant Systems major

The elm tree, a common shade and wind break tree in the U.S., has been dying due to Dutch elm disease. The first strand was brought over from Europe in the 1920s, while the second strand of Dutch elm disease was brought over later. This strand finished killing what trees the first strand had left alive.

Dutch elm disease is a fungus that is spread by the elm bark beetle. The beetles were introduced to the U.S. first, and the fungus shortly followed. The fungus was first introduced when carpenters imported European elm logs with the fungus inside.

Damage from the Dutch bark beetle. Photo: Whitney Cranshaw, Colorado State University, Bugwood.org

Dutch elm disease reached the west coast of the U.S. in 1973. Dutch elm disease has killed 40 million American elm trees. Many of the elms that we planted were street trees to provide needed shade for front yards and streets. Most of these plantings have been killed off.

The introduction of diseases and pests like Dutch elm disease give reason why we need to be careful with international trade. Diseases and pests in certain areas of the world can destroy essential crops if brought into the areas in which the crops are produced. The protection of the global food supply is why there is so much security concerning plants, plant products, soil and containers.

The protection of U.S. food and global food is dependent on us, the normal person, to help stop the spread of devastating diseases and insects. So, remember the next time you travel to clean your shoes, check your souvenirs for tag-a-longs and do not bring soil home with you.


My name is Daniel Zellers. I am a fourth year at The Ohio State University. My major is Sustainable Plant system with a specialization in Horticulture and my minor is in Agribusiness.

More Information

You can go to http://www.apsnet.org/edcenter/intropp/lessons/fungi/ascomycetes/Pages/DutchElm.aspx for more information on Dutch Elm disease. You can visit the USDA APHIS web page for more information on the import and export of plants and animals. The following link is for the USDA APHIS web page https://www.aphis.usda.gov/aphis/home

This blog post was an assignment for Societal Issues: Pesticides, Alternatives and the Environment (PLNTPTH 4597). The views expressed are those of the author and do not necessarily reflect the views of the class, Department of Plant Pathology or the instructor.



Fuel for the Fire, but no Ashes?

By Boden Fisher, Sustainable Plant Systems major

Ash logs in chipping yard, Michigan. Photo: David Cappaert, Bugwood.org

For the past few years Ohioans like myself have not had to look far to get good firewood. Indeed, it is hard to find a park where decreased forest canopies and the stumps of ash trees are not evident. The losses can be credited largely to a beetle whose name designates it as more of a gem than it really is. Since 2003 the Emerald Ash Borer has been extending its domain throughout Ohio, along with other states.

Not only has this epidemic affected the temperate forest biome, as well as residential scenery, but industries such as baseball bat producers are feeling the effects of depleted ash tree supplies.

We have grown accustomed to seeing “Don’t move firewood!” signs near our roadways, but now that the statewide quarantine is lifted, it seems we have given up on the Ash tree. However, the Forest Service has been testing ways fight this catastrophic pest. One strategy was introducing a predatory wasp. Another, is attracting masses of the pest to one host tree by removing the bark, and subsequently disposing of it and its parasitic inhabitants.

The borer, Agrilus planipennis, works by eating away at the vascular tissue within host trees, thus depriving its upper shoots of nutrients and water. The end comes quickly as foliage depletes, along with photosynthesis, and trees are dead within a few years of infestation.

Thankfully, there are insecticides that can help against the beetle, but as in most treatments, early action is necessary to be successful. Treatments are cost effective only for small scale needs, but it is encouraging to see resources available to preserve the trees where plausible.

Being a lifelong Ohioan and lover of shade, I hope to see progress in efforts to halt the loss of one of our native ash trees.

Boden Fisher is an undergraduate student at The Ohio State University, majoring in Sustainable Plant Systems with a specialization in Agronomy. He plans to graduate in 2018 and pursue the advocacy of modern agricultural practices in low-income areas and contribute to advancement of sustainable food systems.

More Information and Sources Cited

This blog post was an assignment for Societal Issues: Pesticides, Alternatives and the Environment (PLNTPTH 4597). The views expressed are those of the author and do not necessarily reflect the views of the class, Department of Plant Pathology or the instructor.


Soybean Cyst Nematode

by Sarah Miller, Sustainable Plant Systems major

Soybean Cyst Nematode disease is a large issue in agriculture today. It is a large unforeseen problem because only the soybean nematode cyst can be seen with the naked eye. Soybean cyst nematode damage is also costing American farmers over one billion dollars a year in crop losses. Many times the soybean cyst nematode can be blamed for other diagnostic problems such as a nutrient deficiency or it could be missed if another pathogen is present.

The soybean cyst nematode is also known by its pathogen name Heterodera glycines. It can infect soybeans and other plants in the legume family. It is found in soil and plants, and has a sedentary endoparasite lifestyle. The sedentary endoparasite lifestyle means that once it is inside the plant root it stays inside the root for the rest of its life cycle.

To know if you have the soybean cyst nematode you should be able to recognize the signs and symptoms. The signs of soybean cyst nematode are the female egg cyst that a very small but can be seen in the soil often by plant roots. The symptoms of soybean cyst nematode disease are stunting, yellowing and overall reduced yields in plants.  Note that this is often similar to other problems.

Another great diagnostic tool to help you see if you have the pathogen in your soils is knowing the lifecycle of the soybean cyst nematode. The soybean cyst nematode overwinters in the soil and begins its life in a cyst, which is a remnant of the female’s body with unhatched eggs inside of it. After the eggs hatch from the cyst and the individual egg itself; it has the normal shape of the nematode and begins to infect a plant around it in the soil. After infecting the plant the soybean cyst nematode continues its lifecycle until till it reaches adulthood, then the males and females will exit the root to mate; the females with become a cyst after their lifecycle is complete.

To help the control the soybean cyst nematode there are a few useful management practices that can be used. Crop rotation can be used to disrupt lifecycles during different growing seasons. Planting resistant crop varieties and applying nematicides can also be helping in fighting the soybean cyst nematode.

This blog post was an assignment for Societal Issues: Pesticides, Alternatives and the Environment (PLNTPTH 4597). The views expressed are those of the author and do not necessarily reflect the views of the class, Department of Plant Pathology or the instructor.

Tomato, Tomahto. Tomato, Tobacco?

by Sarah Miller, Sustainable Plant Systems major

I picked this article to read because I have seen this disease first hand while working at OARDC in Wooster, Ohio while I was helping with various research projects for my internship.  While reading this article I learned that the Tobacco Mosaic Virus is caused by a virus that belongs in the Tobamovirus genus. This virus can then affect many plants, most commonly tomato and tobacco plants. The symptoms that appear on infected tomatoes include mosaic or mottling pattern on leaves, necrosis and yellowing of plant tissues, stunting of plant height, and leaf curling. After the symptoms become present in tomato plants it soon affects the fruit by delaying ripening, shape, and color which results in poor yields.

Tobacco Mosaic can be spread in many ways. It can be spread indirectly by a healthy plant touching a sick plant, workers clothing or hands can carry the virus after smoking or using tobacco products, wounds in plant tissue, or contaminated seed. The virus can also remain infectious for years if the right disease conditions have not been met but, it can begin to thrive again once conditions are conducive for the virus.

To avoid contamination or spread of this virus you should remove all unwanted plant debris and possibly infected soil from where you are trying to grow your crops. Wash all tools and surfaces with soap or a 10% bleach solution. You can also plant cultivars that were bred to be genetically resistant to Tobacco Mosaic and plant infection and disease free seed. Another helpful tip that was discovered is dipping your hands and tools into milk, which has been seen to inactivate the Tobacco Mosaic Virus.

This virus is important to avoid because it would cost many losses in the growth and cultivation of tomato plants. This would cause a lot of economic loss, as well as time that was possibly spend on research toward advancing these plants if they were infected with tobacco mosaic disease.

More information
American Phytopathological Society, apsnet > Tobacco mosaic virus


Sarah Miller is currently a senior studying agronomy at The Ohio State University. In spring 2017 she will graduate with her bachelor’s degree in agronomy.  She plans to start working towards her certified crop advisor certification while working a full time job.

This blog post was an assignment for Societal Issues: Pesticides, Alternatives and the Environment (PLNTPTH 4597). The views expressed are those of the author and do not necessarily reflect the views of the class, Department of Plant Pathology or the instructor.

On MLK Day, remembering George Washington Carver

George Washington Carver

George Washington Carver (ca. 1860s – January 5, 1943). Photo taken by Frances Benjamin Johnston in 1906

Martin Luther King Day is a good time to reflect upon the contributions of George Washington Carver, a groundbreaking agricultural scientist, plant pathologist and inventor.  He was a pioneer in education, research, and agricultural extension.  He developed innovative uses for peanuts and other crops, and he promoted cultural practices such as  crop rotation.

Born into slavery, George Washington Carver overcame tremendous obstacles to become the first black graduate of Iowa State.  He would go onn to become a preeminent scientist and educator at Tuskegee Institute in Alabama.

(this is a modifed repost from previous Martin Luther King holidays)

Read more

The Little Plant Doctor: A Story About George Washington Carver (Holiday House)
Children’s book and activities

Biography Channel
> George Washington Carver








Feeding People’s Mouths

My name is Ben Shaw and I am a junior at The Ohio State University studying Agronomy and Agribusiness. I wrote this blog post because it conveys a serious problem that our nation and the world is going through.

The history of agriculture dates back since around 10,000 BC. Since then, many changes have taken place that have affected how our modern image of food production occurs. This includes selective plant breeding, crop protection technologies, mechanization of farm equipment, and technological advancements over all of the agricultural industry.

GMOs are widely used throughout the world, especially in the US, and are relied upon to feed the growing population. However, arguments are being made around the globe about the unsafe and hazardous conditions that these crops and livestock expose us to. Because of this, many people support organic farming. This farming differs in that no synthetic fertilizers or pesticides are used, and livestock are not treated with antibiotics or other hormones. However, is there even an actual difference in the finished product from conventional and organic agriculture?

Many scientific studies indicate that eating GMO products pose no health risks to humans, and pose no threats. For example, Bt Corn contains a gene from a soil bacterium that will selectively kill insects that eed on the plants. Bt is also completely broken down in human bodies posing no health threat, but using this corn saves growers from using pesticides that are not as selective.

I believe that our real argument shouldn’t be Organic Or GMO, but it should be: How can we combine these methods to support our population?


Stony Brook University. “Sustainable vs. Conventional Agriculture

This blog post was an assignment for Societal Issues: Pesticides, Alternatives and the Environment (PLNTPTH 4597). The views expressed are those of the author and do not necessarily reflect the views of the class, Department of Plant Pathology or the instructor.

Brief Summary of Marestail

By Thomas Lichtensteiger, Sustainable Plant Systems major


Also known as horse weed, marestail is a broad leaf weed in grain crops. It is practically nuisance in soybeans that can get up to 6 feet tall if not controlled.


This weed can be chemically or mechanically controlled. However, because it grows as a basal rosette you must make sure to get the whole root base in order to kill it if using a mechanical system of control. Anything that will kill a broadleaf can be sprayed to kill it.


There is one problem with this weed. In the year 2000 it was first report of it being resistant to glyphosate. This caused a problem that if it was in in a soybean field traited to being tolerant of glyphosate then it would just laugh and keeping growing spreading the resistant population of the weed.


Some advice on how to manage this resistant weed:

  1. Crop rotation with a non-broadleaf crop to allow use of an herbicide with a different mode of action
  2. Planting a glufosinate resistant soybean instead thus allowing for the destruction of the resistant marestail population and help increase yield.


OSU Weed Management

This blog post was an assignment for Societal Issues: Pesticides, Alternatives and the Environment (PLNTPTH 4597). The views expressed are those of the author and do not necessarily reflect the views of the class, Department of Plant Pathology or the instructor.