If you’re a gardener, then you’re probably familiar with the Japanese beetle, Popillia japonica. First discovered in the United States in southern New Jersey in 1916, these small, metallic-green beetles are destructive plant pests that have spread well beyond their entry point. In fact, these beetles are present in most states east of the Mississippi River, and partial infestations occur in states like Arkansas, Iowa, and Kansas. Like any invasive species, the Japanese beetle lacks the natural “checks” that keep it at bay in its home, Japan. As a result, it has become a serious plant pest and threat to agriculture in the United States. Still, methods of controlling the pest have been developed over the years, and strict regulations and monitoring have prevented the pest’s establishment in some southern and western states. What makes the Japanese beetle so destructive? Japanese beetles are damaging both as adults and immatures (called larvae or grubs). The immature beetles develop in soil. These hungry grubs feed on roots of vegetation like grasses and other plants. Grubs often destroy turf grass in areas like golf courses and parks. They are quite efficient at destroying turf – the Japanese beetle is the most widespread turf-grass pest in the United States. Shockingly, it is estimated to cost over $460 million a year to control the beetle of which $234 million is spent on the immature stage alone. When these grubs grow into adults, they become no less destructive! Adult Japanese beetles feed on the fruits and foliage of a wide range of plant species. In fact, Japanese beetles attack over 300 species of plants. Examples include shrubs, fruit trees, field crops, and ornamental trees. As adults satiate their hunger with this vegetation, they create skeletonized leaves along with large holes in leaves. How can we control the Japanese beetle? Control of the Japanese beetle is tricky. As a homeowner, there is no easy or quick fix to get rid of this bothersome beetle. Still, scientists at the USDA have created an integrated pest management (IPM) program that homeowners can utilize. As long as homeowners monitor the beetle populations (both as adults and immatures) and collaborate with neighbors, the program can be effective. IPM is a control method that uses many different tactics to keep pest populations below damaging levels. Rather than eradicate pests, IPM seeks to control them, keeping in mind that reducing pest populations can have a damaging effect on beneficial organisms and the ecosystem as a whole. Therefore, IPM works to minimize impacts on the environment by using many control methods, including biological, cultural, mechanical, and chemical tactics. IPM also includes surveying the pests to keep track of their population size. Because it is clear that the Japanese beetle isn’t going anywhere, IPM allows us to realistically manage the pest. Simply applying chemical pesticides can be wasteful and environmentally damaging, so IPM is a great way to manage the beetle while minimizing environmental harm. So, what does the IPM program for the Japanese beetle entail? Aside from using survey methods like trapping to keep up with the population size, the IPM plan also includes biological controls. This refers to using other organisms to kill the Japanese beetle. Some biocontrol agents include parasites, nematodes, and bacteria. Several of these are commercially available to homeowners. For example, milky spore, Bacillus papillae, refers to the spores of a bacterium that will infect the gut cells and enter the blood of Japanese beetles. Other methods for controlling the beetle include chemical controls (insecticides) and mechanical controls, such as hand-picking the beetles or using traps. It may be possible to simply shake beetles off plants each morning (due to their aggregation behavior) or pick them off by hand and knock them into a jar of soapy water. If choosing to use chemicals, make sure to follow all instructions and read labels carefully. Secondly, if you have any questions about these methods or would like more information, make sure to contract your county extension office. Lastly, there are many plants that are resistant to the Japanese beetle that you can grow. Examples include hickory, red maple, tulip popular, ash, coreopsis, and more. For a more complete list, check out the USDA’s homeowner handbook to Japanese beetle (page 13) or contact your county extension office. So, while the Japanese beetle causes a large amount of damage and is just plain annoying to many gardeners, there are control methods to combat it. They may seem like the bane of your garden, but there are several strategies besides pesticides that you can utilize with the help of neighbors and local extension agents! References Brandenburg, R., & Billeisen, T. (n.d.). Japanese Beetle. Retrieved November 3, 2020, from https://www.turffiles.ncsu.edu/insects/japanese-beetle-in-turf/ Daughtry, M., & Gaster, R. (2019, July 05). Japanese Beetles. Retrieved November 3, 2020, from https://lee.ces.ncsu.edu/2019/07/japanese-beetles-4/ United States, US Department of Agriculture, Animal and Plant Health Inspection Service. (2015, August). Managing the Japanese Beetle: A Homeowner's Handbook. Retrieved November 3, 2020, from https://www.aphis.usda.gov/plant_health/plant_pest_info/jb/downloads/JBhandbook.pdf
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If you read our previous blog post about hemlocks, then you know that the eastern hemlock and Carolina hemlock are currently being destroyed across the Appalachian region due to an invasive pest known as the hemlock woolly adelgid. There have been many efforts to conserve the hemlock tree and protect it from extinction, including insecticides to kill the pest, and biocontrol, where another organism is released into the ecosystem to prey on the invasive species. There is another method currently being used for hemlock conservation, which involves the use of biotechnology. To understand how biotechnology can be used to conserve the hemlock trees, we need to look at another case study from a few years ago: the American chestnut tree. In the early 1900s, the chestnut blight began destroying chestnut trees across the United States. The chestnut blight, Cryphonectria parasitica, is a fungus that essentially suffocates the tree through formation of cankers, inhibiting it from growing more than a couple of feet high. The chestnut blight drove nearly all American chestnut trees to functional extinction in less than 50 years. This problem had two major solutions that were explored, with the first solution being to cross the American chestnut with a similar species that is resistant to the blight. In this case, that other species would be Chinese chestnut. The cisgenic organism that would result from this hybridization would be mostly American chestnut with a few Chinese chestnut genes, hopefully including the gene(s) that help give the tree resistance against the blight. Another solution is to create a transgenic American chestnut. Transgenic trees are genetically modified using genes from an unrelated species, while cisgenic trees are genetically modified with genes from a related species. Scientists found that they could genetically modify the American chestnut and insert a gene from wheat called oxalate oxidase, which gives the tree resistance against the chestnut blight without having to cross it with the Chinese chestnut. There have also been more recent advancements in the field of biotechnology that make the process of genetic modification faster and easier, like CRISPR. CRISPR stands for clustered regularly interspaced short palindromic repeats, and it is a relatively new tool that can be used for genetic engineering, and can potentially be used for species conservation for trees like hemlocks. How does that work? Since this is a complex topic, I’ve reached out to PhD student Bárbara Machado Marques, who is currently doing research with CRISPR at the Forest Biotechnology Group at NC State, to ask for her insight surrounding genetic engineering and its applications for conservation. “In general,” Bárbara began, “biotechnology can be defined as the use of any living organism or biological process for an application. This often involves the manipulation of genetic material. So for example, beer is the oldest biotechnological product made by humans because we take advantage of the fermentation process. Also, insulin is a product isolated from bacteria cells. We’ve genetically engineered this bacteria to produce something we need.” How does CRISPR work, and how does it fall under the category of biotechnology? “The CRISPR system works like DNA scissors,” she explained. “We use a piece of RNA to guide this nuclease called Cas9 into our target DNA in the genome. When you find this target sequence, it is able to clip this piece of DNA and it breaks the two strands of DNA. And because eukaryotic cells have a really cool tool for DNA repair, when it breaks, the cell is able to repair it. And when it does, something happens that usually changes the DNA. In other words, it inserts one or two bases. It often deletes bases, and when it changes this DNA region, usually the gene doesn’t have function anymore.” So, what does this have to do with hemlock trees? “I am currently working with the application of CRISPR technologies into conifer species, which includes Fraser fir, Christmas trees, and hemlock trees,” Bárbara explained. “We use somatic embryogenesis, which is a really cool tool for engineering conifers with all the constraints involved in the transformation of trees. I’m trying to design a protocol for the use of CRISPR on these trees.” It may seem as though genetic engineering for hemlock trees is unnecessary, especially when considering the other methods that are being used to control the HWA spread. Unfortunately, it is possible that those methods may not be enough to protect the hemlock trees on a long term scale. “From what you’ve seen in your research, do you think hemlock trees are in danger of going extinct within the next few years?” I asked Bárbara. “I, unfortunately, think so,” she replied. “Because of climate change, this is a serious issue. The woolly adelgid is actually sensitive to cold, so that’s why the most resistant hemlock trees are located up in the mountains. And it’s the same for Fraser fir. So with climate change, it raises the temperature of everything and it actually helps to spread the woolly adelgid or any other insect. It becomes impossible to control.” I asked, “So when you’re using CRISPR on hemlocks, what genes are you targeting?” “That’s the problem with conifers,” she answered. “Because their genome is not sequenced, so we don’t know which genes regulate pathogen resistance or cold resistance. We don’t know much about the genome of conifers. So the first step of applying CRISPR is to see if it works. We’re targeting a particular gene right now. Once this gene is targeted, the plants turn white because they are unable to produce chlorophyll anymore. So when we target this gene, we can actually see if the CRISPR system is working or not. But other genes that are more relevant for conservation, we don’t know yet. This is more functional characterization of the genes. “The questions are ‘What are the differences between the Chinese hemlock and the Carolina hemlock? What things on the genomes of the Chinese hemlock make it resistant, and how can we use that with CRISPR to introduce this resistance to the [eastern and Carolina] hemlock too?’ And it could be a lot of genes, or it could be only one single base pair.” “How do you feel like your research is going to help conserve hemlock trees and other tree species?” “So, what happened to the hemlock trees here, the Carolina hemlock and the eastern hemlock, is that they didn’t coevolve with this woolly adelgid insect. So, they didn’t get any resistance like the Chinese hemlock. The Chinese hemlocks are resistant because they coevolved with this insect, so they were selected to have some tool inside them to be able to survive with this insect. And because of climate change, there is no time for the eastern hemlock and Carolina hemlock to evolve and be able to naturally develop resistance against this insect. “Here’s where CRISPR is important, because CRISPR can accelerate this process,” she continued. “We can induce mutations that could easily occur naturally, but in a shorter amount of time. Tree breeding programs, artificial selection of traits through crossing of resistant individuals and native individuals, usually take decades to generate good results. By establishing methods for the use of CRISPR as a genome editing tool in trees, the selection of resistant individuals is straightforward, saving the time hemlock trees do not have. So that’s what CRISPR could give to the hemlocks -- time. That’s the main point of using CRISPR.” So, if we look back at the American chestnut case, scientists were successful in using this genetic engineering to take a gene from wheat and insert it into the genome to create a transgenic tree. It appears that as more research on conifers is collected, there is a possibility that something similar to what was done for the chestnut could be done for the hemlocks, whether that means a gene from the Chinese hemlock or a gene from a completely unrelated species is utilized in the process. But will this experiment be well received? “Public reception for the American chestnut wasn't great,” Bárbara noted. “You know, we have a plant that is resistant to the disease, we could apply it to forests, and it’s not there because it’s transgenic. For many years, and even now, transgenics have a very negative image on the general public, for many reasons. Everybody has heard that word and associates it with something bad. So the public acceptance for a plant that was transformed with CRISPR could be greater than it was with the American chestnut because CRISPR is new. It always depends on the public acceptance. If technology has potential, and you do not do the work of explaining and combating fake news, you’ll never be able to apply it.” I asked, “Do you think that being more transparent and upfront about what’s being done will make people feel more accepting of it?” “I think the most important thing for people to know is that we are not doing this without safety and without thinking through what we’re doing,” she replied. “It is scary at some points because there is so much you can do with CRISPR, but we’re not going to throw a genetically engineered tree into the forest without seeing how it interacts with other organisms and what disruptive consequences it could have. It’s important to be clear that there are ethics involved. CRISPR brings a new opportunity for scientists to develop products that do not use transgenic techniques, and are new to the public. Even so, I believe that a main effort has to be made to inform the public about how this technology works and what its potential is.” Works Cited Barakat, A., DiLoreto, D.S., Zhang, Y. et al. Comparison of the transcriptomes of American chestnut (Castanea dentata) and Chinese chestnut (Castanea mollissima) in response to the chestnut blight infection. BMC Plant Biol 9, 51 (2009). https://doi.org/10.1186/1471-2229-9-51 Interview with Bárbara Machado Marques [Online interview]. (2020, October 27). Zhang, B., Oakes, A.D., Newhouse, A.E. et al. A threshold level of oxalate oxidase transgene expression reduces Cryphonectria parasitica-induced necrosis in a transgenic American chestnut (Castanea dentata) leaf bioassay. Transgenic Res 22, 973–982 (2013). https://doi-org.prox.lib.ncsu.edu/10.1007/s11248-013-9708-5 Photography: Dr. Benjamin Smith, Forest Restoration Alliance, threatenedforests.com Joseph OBrien, USDA Forest Service, Bugwood.org The emerald ash borer, Agrilus planipennis, may have a beautiful, metallic green color, but its looks are deceiving. This invasive beetle, which was first discovered in the United States near Detroit, Michigan in 2002, destroys our ash (Fraxinus) trees. In fact, the emerald ash borer has killed tens of millions of ash trees since it was introduced into the U.S. The pesky beetle has traveled from its entry point to many central and eastern U.S. states as well as eastern Canada. In North Carolina, the beetle was initially found in Granville, Person, Vance, and Warren counties in 2013, but it has since spread to about 60 counties. The pest is moving quickly and killing our ash trees in the process. How did the emerald ash borer arrive? The emerald ash borer hails from Asia. It is native to Japan, China, Korea, and parts of Russia. Since this beetle is a wood-borer, it likely entered near Detroit, Michigan through wood packing material made of ash. The beetle is capable of flying to a new host tree after it emerges, but it only moves a few miles per year in this manner. It is transported long distances through ash products. So...we’ve said it before and we’ll say it again: don’t move firewood! Even transporting firewood across county lines can move wood-boring pests significant distances. What’s the big deal? Adults of the emerald ash borer lay eggs on our ash trees. Once these eggs on the bark of the ash trees hatch, the new immature beetles bore beneath the bark and feed on the inside of the tree. Since these hungry beetles eat the tissues that transport food and water within the trees, the movement of water and nutrients is disrupted, and the trees die. The emerald ash borer may kill many of our ash species in North Carolina, including white ash, green ash, Carolina ash, and pumpkin ash. Unlike our native wood-boring beetles, the emerald ash borer will attack either healthy or unhealthy trees, so many of our ash trees are vulnerable. The pest may also attack white fringetree. Even though ash trees make up a small part of our native forests and pure stands of ash are rare in North Carolina, these trees are important. The wood is strong and elastic, so it is very useful and of high value. The wood may be used in products like baseball bats, furniture, bows, and more. In urban areas, ash is particularly important as a street tree, and it can provide benefits to cities by cooling them. Many animals feed on ash leaves and seeds. The loss of ash in the United States would cause many issues. Researchers found that the loss of ash could have significant effects on the productivity of forests and the ability of forests to store carbon (which mitigates climate change). Forests with high numbers of ash will experience large losses of productivity that are not likely to be replaced by the growth of other tree species. There are even human health implications. After studying 15 states in the U.S., researchers found that the death of ash trees caused by emerald ash borer increased human mortality from cardiovascular and lower respiratory illnesses! What are the current management practices? Research is actively being conducted on the best management practices to combat emerald ash borer. For example, at NC State University, scientists are studying ash stands to pick out the trees that survive in the wake of emerald ash borer infestations. Their hope is to figure out if some sort of genetic resistance occurs in certain ash trees, which may help in restoring ash trees. For now, the best management practice is to reduce the spread of emerald ash borer. This may involve quickly detecting the beetle and then cutting down infested trees. The entire state of North Carolina is also under quarantine for emerald ash borer, meaning firewood or other materials that could be infested with emerald ash borer cannot be moved outside of the quarantine area. Insecticides may be used to protect trees when emerald ash borer is closeby. Chemicals may also be used to help individual trees recover, but the recovery is slow and re-treatment must take place each year or two, so this method can be costly. Interestingly, there are three species of parasitoid wasps from China that have been released in the U.S. to combat emerald ash borer (a management practice called biocontrol). These tiny wasps kill emerald ash borer by laying eggs inside or on the beetles’ larvae or eggs. The wasps then consume the immature beetles and kill them. Extensive research was conducted before these wasps were released to ensure they would have no adverse effects on the ecosystem. The NC Forest Service releases the wasps at four different sites. What are the signs and symptoms of emerald ash borer? Signs and symptoms of an emerald ash borer infestation within an ash tree include cracks in the bark, dieback, D-shaped exit holes, epicormic sprouting (sprouting occurring from the main stem of the tree), and increased woodpecker activity (woodpeckers enjoy emerald ash borer as a snack). When the bark is peeled back, tunnels created by emerald ash borer larvae are visible. If you think you have spotted emerald ash borer, you can contact your county ranger through the NC Forest Service or your county extension office. Above all, make sure that you do not transport wood that could be infested! Left: The emerald ash borer spreads quickly and kills ash trees. In this stand in Garner, NC, it is difficult to find a living ash tree. Image: Courtney Smith Right: After peeling back the bark on an ash tree, the emerald ash borer larvae's galleries are visible. Image: Courtney Smith ReferencesDonovan, G. H., Butry, D. T., Michael, Y. L., Prestemon, J. P., Liebhold, A. M., Gatziolis, D., & Mao, M. Y. (2013). The relationship between trees and human health: evidence from the spread of the emerald ash borer. American journal of preventive medicine, 44(2), 139-145.
Flower, C. E., Knight, K. S., & Gonzalez-Meler, M. A. (2013). Impacts of the emerald ash borer (Agrilus planipennis Fairmaire) induced ash (Fraxinus spp.) mortality on forest carbon cycling and successional dynamics in the eastern United States. Biological Invasions, 15(4), 931-944. North Carolina Forest Service. (2017, January 17). Emerald Ash Borer Frequently Asked Questions. Retrieved October 21, 2020, from https://www.ncforestservice.gov/forest_health/fh_eabfaq.htm Oleniacz, L. (2020, September 17). Scientists Pilot Drones in Effort to Save Trees From Invasive Beetle. Retrieved October 21, 2020, from https://news.ncsu.edu/2020/09/scientists-pilot-drones-in-effort-to-save-trees-from-invasive-beetle/ Not all Invasive Species Are Created EqualInvasive species are considered to be one of the leading causes of decline in biodiversity on a global scale. In fact, it’s estimated that approximately 42% of threatened or endangered species in the United States have declined due to invasive species. One major issue is that it takes time for an invasive species to become a problem, and once it’s been identified as a problem it’s typically too late for a swift eradication. Although countless introduced species cause problems, it is important to note that not all non-native introductions carry the same level of devastation for our native wildlife. There are many non-native species that have been introduced that have been able to coexist without outcompeting our native plants, animals and insects. Most people may not even know their beloved crape myrtles are actually native to India, southeast Asia and northern Australia, but it’s true! Crape myrtle was introduced through Charleston, South Carolina in 1970 by the French botanist André Michaux. To date, it does not seem to be having a negative impact on our native wildlife. Entomologist Chris Goforth, the Head of Citizen Science for the North Carolina Museum of Natural Sciences, took some time out of her day to speak with us to shed light on the Asian ladybug, a species that gets a bad rap for being an invasive pest. The Asian ladybug, Harmonia axyridis, is a relative of our native ladybugs. They were brought to the U.S. in 1916, and for nearly 70 years were used to naturally control greenhouse pests. It wasn’t until the late 1980s when an unintentional introduction in New Orleans occurred and provoked an uncontrollable spread throughout the United States. Populations from the southeastern US are thought to be the source for invasions currently spreading across Europe, South America, and Africa. Is there a difference between the terms ladybug and lady beetle? It depends on where you are, but ladybug and lady beetle are used interchangeably. I’ve even heard the term ladybird being used. Some entomologists use the term lady beetle instead of ladybug because they are not true bugs, they are actually beetles. About how many species of native ladybugs do we have here in North Carolina? Of the 500+ ladybug species native to North America, approximately 50 different species of ladybug are native to North Carolina. Most do not resemble the classic ladybug appearance of the convergent ladybug which is why many people may not even recognize an insect they see as being a ladybug. Some are brown, many do not have the common ladybug shape. The twice stabbed ladybug is all black with one red spot on either side of their wings. The polished ladybug is very small. The spotted pink is a really pretty rosy color and has black spots, but most people wouldn’t recognize it as a lady bug because it’s not the right shape or color. Is there only one species of Asian ladybug that has been introduced to the US? There are many different species of ladybug found in Asia. However, the Asian ladybug, Harmonia axyridis, is the only species that has been introduced to North America. We also have the 7-spotted ladybug which is native to Europe and was introduced in the 1950’s. There is so much variation within Asian ladybug species. How can we tell them apart from our native ladybug species? I always tell people to look at the prothorax (the thorax is composed of 3 segments. The prothorax is the first of the three segments, next to the insect’s head). The Asian ladybug’s prothorax is mostly white with no black along the sides, and depending if you are looking at them from the front or the back, you will see a W or M shape on the top. Asian ladybugs have a reputation for being big biters, but all ladybugs have the ability to bite. I’ve been bitten by both and it doesn’t seem like Asian ladybugs bite any more than our native ladybug species. Does the Asian lady beetle seem to be a cause of concern? Are they a threat to our native ladybug species? There is an argument surrounding this, but it's hard to say. Because the Asian ladybug is providing the same service that our native ladybug species provide, most people aren’t worried about them. With that being said, our native ladybug populations are not doing well. The most common ladybugs you find here are the Asian ladybug and the seven-spotted ladybug, not our native ladybugs. As far as I know there is no strong evidence to suggest the decline of our native ladybug species is solely related to the introduction of the Asian ladybug and the seven-spotted ladybug. Land use changes and habitat loss may also be contributing to their decline. In Europe, the Asian ladybug preys on their native seven-spotted ladybug. They are also carriers of a parasitic fungus that is lethal to the seven-spotted ladybug. Here in the United States there is no real concern since it’s one non-native species displacing another non-native species. The Asian ladybugs here are also known to be carriers of different fungus, but it’s unclear whether this fungus is having a negative impact on any of our native ladybug species. The greatest concern is that if all of our native ladybug species are displaced by the Asian ladybug, and the Asian ladybug is the only species remaining if something happens to them, then we will lose all of our ladybugs and the service they provide. Is it worth trying to eradicate the Asian ladybug from our area? Are there any practical methods for managing or removing Asian ladybugs from your property? I wish we could, but at this point, there are so many here it would be too hard to completely eradicate them from North America. I’m of course pro native, and love to see programs like Lost Ladybug that are working to bring back the nine-spotted ladybug. I think it’s more important to try to bring back our native ladybug populations. My hope is that more captive breeding programs develop, and with the information scientists use from citizen science programs like iNaturalist and the Lost Ladybug Project they are able to determine key areas to release native ladybugs back out into the wild with the hope that they overcome the Asian ladybug. Definitely don’t use insecticides because they will also kill off any food for native ladybugs. You can pick them off plants by hand, place them in a jar and put them in a freezer, but it would be a never ending battle because they are everywhere and more are bound to come. Be considerate of others as well. Not everyone is aware that there are non-native species of ladybugs here, and they may not understand why you are killing ladybugs. In the winter, they come into our homes looking for a warm place to get out of the cold, and when one finds a cozy spot they will release pheromones signaling to other ladybugs to join them. If you do find Asian ladybugs gathered in your home the easiest way to remove them is to suck them up with the vacuum cleaner. It’s also important to look for the entry point and block it off to prevent any further infestations in the home. Are there ways we can prevent further spreading of the Asian ladybug? I always encourage people to be mindful when purchasing ladybugs from garden shops to release in their gardens. Make sure the species is native before releasing them, and research the company to see how their ladybugs are harvested. Most of the ladybugs you find in garden shops are collected from areas where populations are more stable like California, but that could ultimately end up having a negative effect on the abundance of the ladybug populations there. What are some ways people can get involved if they were interested in helping to bring back our native ladybug populations? The best thing you can do is plant natives in your garden, and don’t spray insecticides. Having a mix of native flowers in your garden will bring in their prey as well as provide a source of nectar that ladybugs drink when insect availability is low. Also, when you do come across ladybugs, report what you see using citizen science apps like iNaturalist or the Lost Ladybug Project. By just submitting a photograph, you are providing researchers with important information about ladybugs that is used to track populations and determine locations that would be good candidates for the release of captive-breed native ladybug populations. Sources
Bloudoff-Indelicato, M. (2013, May 23). Invasive Lady Beetle Kills Off Competition Using Parasites. National Geographic. Dadam, D., Robinson, R. A., Clements, A., Peach, W. J., Bennett, M., Rowcliffe, J. M., & Cunningham, A. A. (2019). Avian malaria-mediated population decline of a widespread iconic bird species. Royal Society Open Science, 6(7), 182197-182197. doi:10.1098/rsos.182197 Goforth, C., Personal communication, October 9, 2020. Vilcinskas, A., Stoecker, K., Schmidtberg, H., Rohrich, C. R., & Vogel, H. (2013). Invasive harlequin ladybird carries biological weapons against native competitors. Science (American Association for the Advancement of Science), 340(6134), 862-863. doi:10.1126/science.1234032 This beetle may be tiny, but it packs quite a punch using a secret weapon. The redbay ambrosia beetle, Xyleborus glabratus, is a small ambrosia beetle from Asia that was first detected in Georgia in 2002. Since then, it has spread and now exists in areas ranging from Texas to coastal North Carolina. While the beetle is only about 1/16 inch long, it carries a fungus, called laurel wilt (Raffaelea lauricola), that is capable of killing trees in the laurel family. Trees in this family include redbay, sassafras, spicebush, avocado, pondberry, and pondspice. In North Carolina, the deadly disease has only been found in redbay and sassafras, but pondberry is particularly significant because it is federally endangered. To learn more about this destructive beetle-fungus duo, I spoke with Albert “Bud” Mayfield, research entomologist at the USDA Forest Service’s Southern Research Station in Asheville, NC. During our conversation, Bud taught me about these invasive pests as well as his own research. How do the redbay ambrosia beetle and laurel wilt fungus harm trees? Like other ambrosia beetles, the redbay ambrosia beetle carries fungal spores in special pouches in its mouth called mycangia. These beetles are tiny farmers, depositing fungus into their chosen host trees for their larvae to feed on. Normally, ambrosia beetles bore into dead or dying trees to create tunnels and deposit fungal spores for the next generation of beetles. However, the redbay ambrosia beetle attacks healthy trees in North America. The laurel wilt fungus it leaves behind is rightfully named: the spores get into water-conducting tissues, leading the tree to react by closing off vessels, which restricts water flow and causes the tree to wilt. Thus, in trying to stop the movement of the fungal pathogen, the tree dooms itself by cutting off water flow. The tree can wilt in just a few days to a few weeks. One interesting (and scary) fact about the redbay ambrosia beetle is that it only takes one female to start a whole new population. The beetle has quite an interesting method of reproducing; a single female can produce males without mating! Then, the female can mate with her sons to produce other females, and the male and female siblings can mate to create even more ambrosia beetles on their host tree. This means that it only takes one new female beetle introduced to an area to start a whole new, destructive population of redbay ambrosia beetle! What tree species do the beetle and fungus attack? For this pesky beetle, not all trees in the laurel family are equal. The redbay ambrosia beetle reproduces very well in redbay trees, giving it its name. Laurel wilt has caused a huge reduction in redbay trees, killing over 90% of those over an inch in diameter. Redbay trees are important both for natural ecosystems and human cultural traditions. They provide food and shelter for wildlife like bears, turkeys, deer, and more, and two species of swallowtail butterfly rely exclusively on redbay trees. Moreover, these trees are culturally significant for Native Americans, particularly the Seminole Tribe of Florida. Essential and aromatic oils are extracted from the tree for medicinal and other beneficial properties, and the tree has culinary uses. Redbay trees are abundant along the coastal plain, but the redbay ambrosia beetle has started to move inland using sassafras trees. The beetle is now present in upland areas, including in North Carolina, thanks to its use of sassafras. In sassafras, laurel wilt can even move between the roots of trees to reach a new host! As a part of his research, Bud is studying this ability to learn more about how long it may take for the pathogen to spread between the roots of trees. Bud says that state agencies have played an integral role in mapping the spread of laurel wilt. By locating plots with sassafras, the USDA Forest Service has been able to collaborate with state agencies to monitor potential areas that the redbay ambrosia beetle and laurel wilt fungus could attack. What are the signs and symptoms? Trees infected with laurel wilt will have dead, brown leaves. Tiny beetle exit holes will be present on the bark with small “toothpicks” of frass (a sawdust-like excrement) extending from some of them. Finally, dark staining will occur below the bark of the tree. If you think you have trees infected with laurel wilt, contact your county extension office. How did the beetle get here and how can we help reduce the spread? It is likely that the beetle arrived in the Southeast through wood pallets or packing crates. Since it is a wood borer, the redbay ambrosia beetle can be easily transported long distances through wood. For this reason, Bud says the best thing you can do to help is avoid moving firewood. While the beetle can fly from tree to tree, it is transported long distances through wood. According to Bud, even if you just move firewood across county lines, you have the potential to move the pest a significant distance. Management options are limited. There is no cure once a tree has laurel wilt, and it will often die in a few months. Therefore, preventing the spread is incredibly important, and we can all help by buying and burning local firewood! Left: Laurel wilt causes the leaves of trees to wilt, as its name implies. Leaves often look brown and dead. Image: Albert (Bud) Mayfield, USDA Forest Service, Bugwood.org Middle: Small "toothpicks" of frass, a sawdust-like excrement, are signs that redbay ambrosia beetle could be present. Image: James Johnson, Georgia Forestry Commission, Bugwood.org Right: The laurel wilt fungus, which infects the water-conducting cells of trees, causes dark staining beneath the bark. Image: R. Scott Cameron, Advanced Forest Protection, Inc., Bugwood.org ReferencesMayfield, A. E. (2020, October 02). Laurel wilt [Online interview].
North Carolina Forest Service. (2020, August 19). N.C. Forest Service collaborates with USDA Forest Service to monitor the spread of laurel wilt. Retrieved October 06, 2020, from http://info.ncagr.gov/blog/2020/08/19/nc-forest-service-collaborates-with-usda-forest-service-to-monitor-the-spread-of-laurel-wilt/ USDA Forest Service. (2020, June 10). Distribution of counties with laurel wilt. Retrieved October 06, 2020, from http://southernforesthealth.net/diseases/laurel-wilt/distribution-map . You may have recently seen photos of the hammerhead worm pop-up on your Facebook or Instagram feed and wondered ‘what on Earth is this thing?’ Looking like something that’s escaped the Upside Down from the Netflix series Stranger Things, it’s no doubt that this creepy looking creature would create quite a buzz. You may also be surprised to learn that the hammerhead worm is not a segmented annelid like our beloved earthworms. They are actually in the Phylum Platyhelminthes, and are more closely related to the bright and colorful flatworms found cruising around on the seafloor. So a more appropriate common name for them would be the hammerhead flatworm. Over 910 terrestrial (land living) hammerhead flatworm species have been discovered to date, with many more waiting to be described as a species. Currently, there are four known hammerhead flatworm species that have been introduced in the United States, but the two most commonly encountered are Bipalium adventitium occurring across the northern portion of the US and Bipalium kewense, which is found across the southeast and California. Hammerhead flatworms are easily identified by their distinctive fan or shovel shaped head and their long, flat body. The number of stripes that run along their back and the shape of their head helps researchers determine what species has been encountered. Most species of hammerhead flatworms range in size from 5-8cm, but the Bipalium kewense that has invaded the southeast can reach upwards of 20-cm in length. On the underside of their body, hammerhead flatworms have a large ‘creeping sole’ that they use to glide smoothly through the soil and across the ground. Their motion mimics that of a snake rather than a typical worm, which is why some people confuse the larger species found in the southeast as being a snake. In a study published in 2014, Dr. Amber K. Stokes, an Associate Professor in the Biology Department of CSU Bakersfield, discovered that both Bipalium adventitium and Bipalium kewense possess a potent neurotoxin called tetrodotoxin. This toxin is also found in pufferfish, the blue-ringed octopus, and rough-skinned newts, but remarkably it is not known to occur in any other invertebrate on land. Hammerhead flatworms are considered an apex predator as they have almost no known natural predators. They are known to capture and immobilize prey much larger than themselves by entangling it in slimy secretions of this neurotoxin. Once their prey is mostly immobilized, the flatworm releases digestive enzymes, then consumes the liquefied tissue. Unlike insects, animals and humans, flatworms have only a single orifice, or body opening, so once digestion is complete, the waste goes out the same way it came in. How did they get here?Surprisingly, Bipalium kewense are not a new invasive species in the southeast. They are native to the moist, tropical jungles and temperate woodlands of southeast Asia. With our climate being so similar, they have been able to easily establish themselves here in the southeast, and are commonly found in dark, cool, moist areas under objects such as rocks, logs, and leaf litter. Although an exact date is unclear, it is believed that they were unintentionally introduced through the international ornamental plant trade in the late 1800s. Apparently, they were reported as being so plentiful in New Orleans in the 1960's that they were commonly used as demonstration material in zoology classes. Are they a threat?At one time, researchers were concerned hammerhead flatworms might cause damage to our native plant communities. Over time, it has become apparent that their presence has the potential of causing greater harm to the rich biodiversity that exists in the southeast by endangering our native soil-living species (earthworms, snails, slugs, insect larvae, and several arthropods, including isopods and springtails), which will ultimately impact our native plant and wildlife communities. As of now, there is no known population decline in any of their prey species, including our earthworms. However, this may change as hammerhead flatworms continue to expand their range and their populations continue to grow. What is being done to stop them?Almost every year new sightings of hammerhead flatworms are reported, and in the southeast they have no known natural predators to keep their populations in check. Up until 2012 it appeared as though nothing preyed on these flatworms. Recent experimental work by PhD student Piter Boll at Universidade do Vale do Rio dos Sinos in Brazil discovered that Rectartemon depressus, a carnivorous snail, seeks out and preys on several species of flatworm including Bipalium kewense, the hammerhead flatworm that has invaded the southeast. Although this discovery is encouraging, there is no plan to release this snail into North America. Although the United States’ Animal and Plant Health Inspection Service Agency (APHIS) has set regulations for controlling the transport of ornamental plants and animals to minimize the spread of invasive species, there is no current task force in place focused on controlling the spread of hammerhead flatworms. What can we do?Unfortunately, our present knowledge is limited, and their long term ecological impact is still not well understood. Because of this, curbing their spread will continue to be a challenge in the future if their populations continue to grow. For any budding entomologists out there this may be your shot! Fortunately, some known methods used to control slugs have been found to also work for exterminating hammerhead flatworms. Several flatworm experts have suggested the use of orange essence has proven to be an effective way deter them from taking up residence on your property. Additionally, they can be killed quickly with salt. Another study found that immersing potted plants known to contain a hammerhead flatworm infestation in water heated to 93 degrees for at least five minutes is fully effective, killing them within one hour. Lastly, please avoid cutting them as a method to rid them from your property. Hammerhead flatworms are able to reproduce asexually(without a mate) by a process called fragmentation. During fragmentation, the back end of the hammerhead flatworm separates from the rest of its body. While the front half grows a new tail, the back end moves around headless until it grows a new head, which takes about 10-15 days. Cutting them may inadvertently encourage reproduction. As always, here at Invasive PestWatch NC we encourage you to be careful. If you suspect an infestation on your property you can always seek professional assistance by contacting your local University Extension Department. You can also help scientists that are actively tracking the spread of hammerhead flatworms by uploading images to iNaturalist. Sources:
Ducey, P. K., McCormick, M., & Davidson, E. (2007). Natural history observations on bipalium cf. vagum jones and sterrer (platyhelminthes: Tricladida), a terrestrial broadhead planarian new to north america. Southeastern Naturalist, 6(3), 449-460. doi:10.1656/1528-7092(2007)6[449:NHOOBC]2.0.CO;2 Ducey, P. K., West, L., Shaw, G., & De Lisle, J. (2005). Reproductive ecology and evolution in the invasive terrestrial planarian bipalium adventitium across north america. Pedobiologia, 49(4), 367-377. doi:10.1016/j.pedobi.2005.04.002 Harrison, L. (1 C.E.). Hammerhead worms are an invasive species. http://blogs.ifas.ufl.edu/wakullaco/2019/01/31/hammerhead-worms-are-an-invasive-species/ Gastineau, R., Justine, J., Lemieux, C., Turmel, M., & Witkowski, A. (2019). Complete mitogenome of the giant invasive hammerhead flatworm bipalium kewense.Mitochondrial DNA. Part B. Resources, 4(1), 1343-1344. doi:10.1080/23802359.2019.1596768 Gastineau, R., Justine, J., Thery, T., Gey, D., & Winsor, L. (2019). First record of the invasive land flatworm bipalium adventitium (platyhelminthes, geoplanidae) in canada.Zootaxa, 4656(3), 591-595. doi:10.11646/zootaxa.4656.3.13 Lemos, V. S., Canello, R., & Leal‐Zanchet, A. M. (2012). Carnivore mollusks as natural enemies of invasive land flatworms. Annals of Applied Biology, 161(2), 127-131. doi:10.1111/j.1744-7348.2012.00556.x Sluys, R. (n.d.). Invasion of the Flatworms. American Scientist. https://www.americanscientist.org/article/invasion-of-the-flatworms Stokes, A. N., Ducey, P. K., Neuman-Lee, L., Hanifin, C. T., French, S. S., Pfrender, M. E., . . . Brodie Jr, E. D. (2014). Confirmation and distribution of tetrodotoxin for the first time in terrestrial invertebrates: Two terrestrial flatworm species (bipalium adventitium and bipalium kewense). PloS One, 9(6), e100718-e100718. doi:10.1371/journal.pone.0100718 This beetle may look cool, but it is destructive! The Asian longhorned beetle, Anoplophora glabripennis, is a beetle native to China and Korea. First detected in the U.S. in New York in 1996, this beetle is capable of destroying over 29 species of hardwood trees! It prefers maple and boxelder (Acer) but can also attack birch (Betula), elm (Ulmus), ash (Fraxinus), poplar (Populus), and more. Given this beetle’s talent for destroying a wide range of trees and the fact that maple and boxelder comprise the second-most abundant group of trees in our state, it is important that North Carolinians stay on the lookout for the Asian longhorned beetle. The Asian longhorned beetle (ALB) has travelled to Illinois, Massachusetts, New Jersey, Ohio, and, most recently, South Carolina (discovered near Charleston in June 2020) since its original introduction to New York in 1996. Most infestations in the North came from Asia, but it is unclear if the recently discovered infestation in South Carolina, which has likely existed for about 7 years, came from Asia or another state in the North. More research is needed to understand the Asian longhorned beetle’s life cycle and traits in the Southeastern United States, which could be accomplished by researching the recent infestation in South Carolina. So, how is the ALB destructive? Unlike other wood-boring beetles such as the emerald ash borer, the Asian longhorned beetle larvae burrow deep within the hardwood and cause structural damage. While most longhorned beetles feed on trees that are already stressed or dying, ALB feeding can kill healthy trees! Other pests may only go through to the cambium layer (a layer of a tree just beneath the inner bark that controls growth), but the Asian longhorned beetle larvae burrow deep into the tree where they spend their entire immature life stage. Larvae destroy the quality of the wood, and large numbers of hungry beetles can even kill trees by girdling them and cutting off nutrient and water flow. I spoke with Amy Michael, state survey coordinator for the Cooperative Agricultural Pest Survey (CAPS) with the USDA Animal and Plant Health Inspection Service, to learn more about the Asian longhorned beetle. According to Amy, the discovery of the pest in South Carolina is concerning for our state because, if it came from a northern state, then it would have had to pass through North Carolina to reach the area near Charleston. The beetle poses a risk to health and safety due to its extraordinary ability to kill and weaken the structural integrity of hardwood trees. In this part of the country, strong storms and hurricanes are a threat. If a hurricane came through, high winds could easily knock off large branches of ALB-infested trees, potentially increasing property damage or harming people. Amy says that it is important for North Carolinians to look out for the signs of Asian longhorned beetles. While state and federal agencies complete frequent surveys, many infestations of ALB (including the recently spotted one in South Carolina) were discovered by landowners. Sap flows through a large portion of the beetle’s preferred snacks, maple trees, so it takes time for these trees to die or show symptoms of attack. In fact, it may take several years for symptoms to appear! At first, the trees are just stressed, but eventually they become damaged to the point of no return. According to the NC Forest Service, infested trees do not recover or regenerate. There are several signs and symptoms of the Asian longhorned beetle to watch for. They include:
If you see any of the signs or symptoms listed above, contact your county extension office. Amy says that she would rather receive a call about a false ALB sighting than have ALB go unnoticed in our state. You can also report sightings by using the new reporting tool on the NCDA&CS website or by sending a photograph to [email protected]. Unfortunately, management of the Asian longhorned beetle isn’t pretty. Getting rid of the beetle requires removing and destroying all infested trees. Even though this may seem drastic, it is better to remove the trees and effectively rid the area of the beetle rather than allow it to spread to other areas and kill more unsuspecting host trees. So, if you see signs of ALB, make sure to report them to prevent this tree destruction. Above all, don’t move firewood! Because it is a wood-borer, Asian longhorned beetle can travel through firewood and other wood materials, even if it does not seem like the pesky beetle is present. ALB can live in untreated firewood for months, so moving firewood could help the beetle arrive in new areas. Buy local firewood instead. While the ALB is a scary pest, eradication has been achieved in the past with early detection. Since ALB is closer to NC than ever before, it is important for North Carolinians to be on the lookout so we can detect the pest early if it is indeed in our state. Amy says that, while not moving firewood is the best and easiest way you can help out, it is also great to get involved with your county extension office. Know who they are, where they are, and what they do because they have all the information on pests like ALB. And help them out by keeping an eye on your maple trees! Left: ALB exit holes are perfectly round and about the width of a #2 pencil. Image: Dennis Haugen, USDA Forest Service, Bugwood.org Middle: Adult Asian longhorned beetles gnaw pits before depositing eggs within them. Image: Melody Keena, USDA Forest Service, Bugwood.org Right: Frass, an excrement that looks like sawdust, is often present on trees with Asian longhorned beetle. Image: Kenneth R. Law, USDA APHIS PPQ, Bugwood.org Written by Courtney Smith Edited by Amy Michael References Paine, T., & Hoddle, M. (2020, January 19). Asian Long-Horned Beetle, Anoplophora glabripennis. Retrieved September 23, 2020, from https://cisr.ucr.edu/invasive-species/asian-long-horned-beetle United States, North Carolina Forest Service, Forest Health. (2020, June). Pest Watch: Asian Longhorned Beetle Found in Neighboring State. Retrieved September 22, 2020, from https://www.ncforestservice.gov/forest_health/pdf/FHN/FHN06222020.pdf About the Hemlocks and How the HWA Arrived If you’ve ever visited the Appalachian mountains, the chances are that you’ve seen a hemlock tree before. They tower over the landscape and were once incredibly abundant across forests in the eastern United States. There are two main hemlock species found in the Appalachian region: the eastern hemlock and the Carolina hemlock. These endemic species are a vital part of forest communities, and are essential for maintaining and moderating climate as well as providing habitat for wildlife. Unfortunately, these trees are currently being threatened by an invasive species. The hemlock woolly adelgid (HWA) is slowly destroying populations of hemlocks across the eastern United States. This tiny, non-native pest was brought from Japan in the 1920s, and over the course of several years, made its way into the hemlock tree populations in U.S. and Canadian forests. The HWA is able to kill hemlock trees by attaching itself to the base of the needles of the tree’s leaves and feeding on the nutrients while simultaneously restricting the water circulation within the tree. I spoke with PhD student Austin Thomas, who studies eastern hemlock and fraser fir trees, and asked him about how badly damaged the hemlock populations in the Appalachian region are. “To be honest, there's already only about 10% of their original [eastern] hemlock biomass that there was 60 years ago,” Austin explained. “We've already lost American chestnut, which was also primarily a riparian species at least in the southern Appalachians, and now we've lost Eastern hemlock. It hasn't caused a complete collapse yet, but what's the next species to go [extinct], and will that be the one that kind of breaks the whole system and causes the ecological collapse? That's hard to measure. But we're losing diversity, basically.” Unfortunately, the HWA are rapidly making their way through hemlock populations, and the trees have no natural defenses against the pest. What’s Being Done About It? Dr. Benjamin Smith is a research scholar for the Forest Restoration Alliance who oversees the day to day operations of their research program. I spoke with him to find out what’s being done to combat the HWA in the Appalachian region. Dr. Smith oversees “Certainly, there have been enough trees that are chemically treated that we're not going to lose hemlocks,” he began. “But that's going to require ongoing effort. There is bio control that's been utilized for quite a while, and time is going to tell how effective that is. So it may be helping it, but it's really hard to say. "We've also seen the adelgid populations and suffered a little in the last few years with cold winters. And in general, we're tending to see the health of the hemlocks rebounding and bit, just from that that's likely to be just a short term improvement. I don't think there's a risk at this point that we're going to completely lose it. But it certainly is just a very small shadow of its former glory.” “It's a really daunting task,” Austin added while we discussed the challenges in protecting the hemlocks. “And when it's a species that you know has ecological importance, but is not a keystone species or a huge commercial forestry species, it's hard to get funding and get people to care.” How Can You Get Involved? Are there any ways that people can help protect these trees from the HWA in their ordinary lives? As it turns out, there are a few small things that could make a big difference. Many forest pests are spread through human activity, particularly when people move firewood across long distances. “Certainly, the ‘Don't Move Firewood’ type campaigns can help slow down the spread,” Dr. Smith explained. “But it's at this point it's pretty much going to spread everywhere that it can survive.” By purchasing firewood locally, you can ensure that you aren't transporting a forest pest native to one area to another place where it would be considered invasive. PhD student Austin Thomas also works for Hemlock Nature Preserve in Cary, NC, which is a great resource for people who want to learn more about the hemlock trees. This unique park has the eastern-most population of hemlock trees, which typically cannot survive in the Piedmont region. The reason they are able to thrive in a small park in Cary is due to the landscape. The stream at the bottom of the bluffs helps to cool down the area, which mimics the climate of the Appalachians and makes the environment more suitable for hemlocks to thrive in. “This is a very well defined micro climatic niche for the hemlock in this very, very small area,” Austin explained. “But also, it's a pretty small population, there's less than 300 individuals living currently In that hemlock bluffs, and only about 20 of the trees have reached reproductive maturity.” When I asked about some ways that people could help protect the trees when visiting a place like the Hemlock Bluffs Nature Preserve, he responded,“The biggest thing is respect the signs that say, ‘Please don't go off trail,’ because erosion is huge. Walking on and trampling all the soil is going to kill the trees. Respect the trails, because they're there for a reason.” Since this park is such a unique feature in Cary, it has been a very beneficial place for research surrounding hemlocks and HWA to take place. I asked Austin, “And focusing on the Hemlock Bluffs, and then the microclimate and the tiny population that's so far away from, from where the hemlocks naturally grow, why would you say that it's important for those to be preserved?” “I would argue that anything that gets people excited about their local environment is an important thing to preserve and it's an important lesson in the ecology and natural history of the area,” Austin replied. In summary, there’s a lot of challenges involved with trying to preserve the hemlock trees. However, there has been some success in managing the HWA, which means there is still hope that many of the populations can still be saved. If you’d like to get involved, you can always visit the Hemlock Bluffs Nature Preserve in Cary. Also, remember not to move firewood over long distances or plant hemlock trees outside of their natural habitat. Sources: Alexander M. Evans (2008) Growth and Infestation by Hemlock Woolly Adelgid of Two Exotic Hemlock Species in a New England Forest, Journal of Sustainable Forestry, 26:3, 223-240, DOI: 10.1080/10549810701879735 Don't Move Firewood. (n.d.). Retrieved September 16, 2020, from https://www.dontmovefirewood.org/ Forest Disturbance Processes. (2020, March 11). Retrieved September 16, 2020, from https://www.nrs.fs.fed.us/disturbance/invasive_species/hwa/ Forest Restoration Alliance. (n.d.). Retrieved September 16, 2020, from https://threatenedforests.com/ Havill, N. P., Vieira, L. C., & Salom, S. M. (2014). Biology and control of hemlock woolly adelgid. Morgantown, West Virginia?: United States Department of Agriculture, Forest Health Technology Enterprise Team. Thammina, C., Conrad, K.P. & Pooler, M.R. Genetic diversity of the U.S. collection of Chinese hemlock Tsuga chinensis (Franch.) E. Pritz. based on simple sequence repeat markers. Genet Resour Crop Evol 66, 847–855 (2019). https://doi-org.prox.lib.ncsu.edu/10.1007/s10722-019-00752-2 Zoom Interview with Austin Thomas [Online interview]. (2020, September 5). Zoom Interview with Dr. Ben Smith [Online interview]. (2020, September 15). Photos: Bruce Watt, University of Maine, Bugwood.org While surfing the Internet in 2020, you’ve likely seen all kinds of articles about COVID-19, toilet paper shortages, and, most recently, “murder hornets.” The Asian giant hornet, Vespa mandarinia, was discovered in Washington state in December 2019, and two new workers were found in August 2020. Many in North Carolina are worried about the invasive hornet, which is the largest hornet ever discovered. However, the North Carolina Department of Agriculture and Consumer Services is monitoring for these “murder hornets,” and they have not been discovered in our state. We have several large wasps and hornets (and even some flies) in North Carolina that may fool North Carolinians, but don’t be alarmed! You can easily tell these look-alikes apart with a few defining characteristics. The Asian giant hornet is the world’s largest hornet, measuring up to two inches in length. These hornets are bright orange or yellow in color with a dark brown thorax (the portion where the wings and legs connect). They have notched eyes that are far from the back of the head, and their abdomen is covered in continuous brown and orange stripes. There are a few native wasp species in North Carolina that are comparably large. One example is the cicada killer wasp (Sphecius speciosus), which can reach up to almost two inches in length. But size does not indicate danger - unless you are a cicada (a large, noisy insect in North Carolina), the cicada killer wasp will not harm you! Likewise, there are several other insects, such as the introduced European hornet (Vespa crabro), that are commonly mistaken for “murder hornets.” Even a fly species, the red-footed cannibal fly (Promachus rufipes), deceives people! Still, with a careful eye and a few resources, it is possible to tell the difference. So, why does the Asian giant hornet elicit so much alarm? Besides its large size, many are worried about the hornet because it threatens other insect populations, such as the European honey bee. The European honey bee is not native to the United States, but it is an important pollinator for our agriculture. Asian giant hornets are predators of honey bees, and they are capable of destroying entire hives in just a few hours. These predators send out pheromones, or chemical messages, to other Asian giant hornets, signaling them to attack and rapidly kill honey bees. Japanese honey bees have evolved to fend off Asian giant hornets and respond to these pheromones, but European honey bees haven’t. Without any strong defenses, European honey bees can’t withstand the wrath of Asian giant hornets. It is unknown exactly how the Asian giant hornet would affect other insect populations in the U.S., but it is likely that it would prey upon our native bees, and its impact on European honey bees is enough to worry beekeepers! No one knows for sure how the Asian giant hornet got to Washington state, but some suggest it could have ended up in packing material or been brought illegally for food or medicinal purposes (the nutritious larvae and pupae of the hornet are often eaten in Asia). Researchers in Washington created a model to predict whether the Asian giant hornet could establish itself in the United States. They suggest that the hornet is most likely to occur in areas with low to warm annual temperatures and high precipitation, which exist in most of the eastern part of the country. Since Asian giant hornets are so concerning to beekeepers, professionals across the country are monitoring for these insects. It is understandable that many North Carolinians are worried about the “murder hornet,” but, as of now, these hornets are not in North Carolina. If you see a large wasp, keep in mind that we have several large species in North Carolina, and try to keep your eyes peeled for defining characteristics like colors and patterns. Above all, don’t just kill any large insect you see...most of them are beneficial! Written by Courtney Smith Edited by Dr. Matt Bertone, Director, Plant Disease and Insect Clinic, NCSU References
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March 2023
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