Sustainable Pest Control for Japanese Beetles
Japanese Beetle munching on a flower.
Japanese beetles (Popillia japonica) are a notorious pest for flower farmers, causing extensive damage to a wide variety of plants. Recognizable by their metallic green and bronze bodies, these beetles can wreak havoc during their adult phase, typically in June in our area (USDA Hardiness Zone 7b). Because they emerge in our area in June, some people mistake Japanese Beetles for June Bugs. June Bugs are beetles, but they are much larger and native. June bugs aren’t really anything to worry about. I find them quite beautiful actually. Unlike June bugs, Japanese Beetles are quite destructive. They skeletonize leaves and damage flowers, making it crucial for farmers and gardeners to find effective pest control methods or not since they have such a short season. You have to determine your tolerance level for these pests and whether or not you’d like to deploy control measures or not. I saw my first Japanese Beetles this week (right on time!) so I thought I’d share some pest control methods that won’t harm any beneficial insects or the environment and most importantly tips for effective steps you can take against these pesky pests.
History of Japanese Beetles
Japanese beetles (Popillia japonica) are native to Japan, where they are relatively minor pests due to natural predators and environmental conditions that keep their population in check. However, they were inadvertently introduced to the United States in 1916, likely as larvae in the soil of imported ornamental plants. The first documented infestation was in a nursery in Riverton, New Jersey. Since their introduction, Japanese beetles have spread across much of the eastern and central United States, becoming significant agricultural and horticultural pests due to the lack of natural predators and favorable environmental conditions for their growth and reproduction.
Identifying Japanese Beetle Damage
The most telltale sign of Japanese beetle infestation is skeletonized leaves, where only the veins remain. They are particularly fond of roses, fruit, and corn, among other plants. Japanese Bettle larvae like feasting on grass and other plant roots. Spotting these signs early can help in managing the infestation before it gets out of control.
Consider using one or more of the following sustainable pest control methods:
Cultural Control
Implementing crop rotation can disrupt the lifecycle of Japanese beetles, making it harder for them to establish. Additionally, using trap crops—plants that attract beetles away from your main crops—can help protect your valuable flowers. Some examples of trap crops include geraniums, certain soybeans, zinnias, and marigolds. If you’re growing produce, planting roses nearby can also be a viable trap crop solution. Annual geraniums have a paralyzing effect on Japanese Beetles making them particularly useful as a trap crop.
Mechanical Control
Hand-picking beetles early in the morning when they are less active is a simple yet effective method. This is the method that I use the most. I take a cup of soapy water outside with me and gently knock them into the cup. The soap prevents them from crawling or flying out. While pheromone traps can attract beetles, they should be used strategically to avoid drawing more beetles into your garden than necessary. Pheromone traps are very effective but put them as far away from your garden as you can so you don’t create a bigger problem. Your neighbor’s yard is best if they don’t grow their own crops of course. You can purchase pheromone bags here.
Biological Control
Introducing beneficial nematodes to your soil can target beetle larvae before they mature. Encouraging natural predators, such as birds, can also help keep the beetle population in check. Milky spore disease is another biological method, infecting and killing beetle larvae. Nematodes can be purchased here, but they need to be applied while the beetles are in their larval stage. Milky Spore can be purchased here.
Botanical Insecticides
Neem oil acts as a deterrent and is safe for most beneficial insects. Insecticidal soaps can reduce beetle populations on contact without leaving harmful residues. To protect pollinators, apply in the evening when pollinators are not active. Additionally, follow the product instructions. Any oil-based product can burn your plant if applied when the weather is too hot. Personally, I use products as a last resort. You can purchase Neem Oil here. You can purchase insecticidal soap here.
Organic Pesticides
Pyrethrin-based products are effective but should be used sparingly to minimize harm to non-target insects. This should be a last resort. Again, I don’t control Japanese Beetles other than hand-picking them because their season is so short. I tolerate them. If you cannot tolerate them, here is a product that you can use to fight those beasts.
Companion Planting
Certain plants, like garlic, chives, and tansy, can repel Japanese beetles, making them excellent companions for susceptible plants.
Long-term Strategies
Maintaining healthy soil through organic matter and proper fertilization makes plants more resistant to pests. Increasing plant diversity in your garden can also reduce the likelihood of pest outbreaks, creating a more balanced ecosystem.
Sustainable pest control is not only effective but also beneficial for the environment and your garden’s health. By implementing these strategies, you can manage Japanese beetles while maintaining a thriving, eco-friendly garden. Until next time, Flower Friends!
Keep Blooming,
Nicole Dillon
Breemar Flower Farm | Ashland, VA
Sources:
USDA APHIS. (2015). Japanese Beetle: Biological Control. Retrieved from USDA APHIS.
Held, D. W., & Potter, D. A. (2004). Floral affinity and paralyzing effect of geraniums (Pelargonium spp.) on Japanese beetles (Popillia japonica). Environmental Entomology, 33(4), 870-878. DOI: 10.1603/0046-225X-33.4.870
Hammond, R. B., & Pedigo, L. P. (1982). Response of the Japanese beetle (Coleoptera: Scarabaeidae) to soybean trap crops and phenological resistance. Journal of Economic Entomology, 75(4), 780-783. DOI: 10.1093/jee/75.4.780
Potter, D. A., & Held, D. W. (2002). Biology and management of the Japanese beetle. Annual Review of Entomology, 47(1), 175-205. DOI: 10.1146/annurev.ento.47.091201.145153
Held, D. W. (2004). Relative susceptibility of woody landscape plants to Japanese beetle (Coleoptera: Scarabaeidae). Journal of Arboriculture, 30(6), 328-335. Retrieved from Journal of Arboriculture
Potter, D. A., & Held, D. W. (2002). Biology and management of the Japanese beetle. Annual Review of Entomology, 47(1), 175-205. DOI: 10.1146/annurev.ento.47.091201.145153
Vittum, P. J., Villani, M. G., & Sadof, C. S. (2019). Japanese Beetles: Popillia japonica. Virginia Cooperative Extension. Retrieved from https://www.pubs.ext.vt.edu/2902/2902-1101/2902-1101.html
