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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AuthorWe are a group of NC State University students committed to spreading awareness about the invasive species that inhabit or threaten North Carolina. Archives
December 2020
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