With an appetite for over 300 species of plants, and doing hundreds of millions of dollars in damage every year in the United States, Japanese beetles are a serious pest. They are often described as having no limit to what they’ll eat. These beetles love to munch on leaves, flowers, fruits, turfgrass, roots, and more! They’re classified as an invasive species. How do you keep Japanese beetles away from your beans and other plants? Keep reading to learn more!
11 Natural Methods to Keep Japanese Beetles Away
1. Manage Grubs
Adult female beetles can lay as many as 60 eggs during the mating season. Japanese beetles start as small, white grubs. Once they are an inch long, they’re full-sized and can be quite destructive. By that time it’s often too late. If you see dying grass in August, this is an early sign of grub damage. You’ll need to check under the grass to identify the cause and if you see white grubs, you have a Japanese beetle infestation.
White grubs should be treated in summer. You can use roundworms, or parasitic nematodes, to naturally fight the infestation. Apply these once the white grubs are present. As nematodes are susceptible to warm weather, you’ll want to use them in the area during cooler and overcast days. You can also use a bacterial strain like bacillus thuringiensis galleriae to naturally fight the grubs. This bacteria secretes a toxin that can kill both white grubs and adult beetles.
2. Managing Adults – Identify and Understand Their Preferences
Japenese beetles were transported over to the United States from Japan in the early 1900s. They are mostly found on the Eastern side and have multiplied within New Jersey, North Carolina, Tennessee, Ohio, Georgia, Mississippi, Texas, Oklahoma, Kansas, Nebraska, and South Dakota. They’ve also been sighted on the West Coast. They are drawn to climates like that of Japan’s, with wet, rainy summers.
In adult form, Japanese beetles are an inch long with a metallic sheen. They have green bodies with coppery wings. They live mostly in moist soil and are sensitive to dryer, warmer environments. They don’t have many natural predators, which is why they’ve been able to spread so quickly. These beetles are most prominent during the warmest summer months. Once you have a good handle on what they like, you’ll have a better understanding of your chances of an infestation.
3. Watch Over Your Plants
Now that you know how to identify adult beetles, it’s important to watch for them. Japanese beetles are attracted to the odor of ripened and diseased fruits. Therefore, one of the best ways to prevent them is simply to keep your garden healthy by removing ripe and diseased fruits, and also by keeping a watch over your plants for the beetles.
Once a single Japanese beetle makes its way to your crops, more will follow and they will multiply quickly. If you find adults targeting your crops, remove and kill them.
4. Pick the Beetles Off By Hand
One of the easiest solutions to Japanese beetle removal is to pick them off of the plants yourself. This is a top recommendation for removal. These beetles are not quick movers, nor do they bite or pinch. Therefore, you can use your hands and pluck them off. You must avoid squeezing or crushing them, as the agitation might attract more beetles. Collect them in a container and use humane methods to safely kill them.
5. Spray a Solution of Soap and Water
A simple mixture of soap and water is a good way to kill Japanese beetles. This solution is safe and effective and works by suffocating them. The best way to create this is to mix 2 tablespoons of a standard dish soap with a gallon of water. Then use a spray bottle to directly target the beetles on your crops. The beetles will fall and become safe food for birds and other predators.
6. Spray Neem Oil
Neem oil is a popular organic solution for many gardening issues. Neem oil is non-toxic for humans but toxic for many pests. You can spray neem oil directly onto the impacted crops before the beetles grow into the adult stage. The male beetles will ingest the oil and pass it on to the eggs. This will kill the larvae before they have a chance to traverse into adulthood. Therefore, you’ll want them to ingest the oil before they mate.
7. Keep Birds in the Area
Guinea fowl, ducks, and other types of birds are some of the few natural predators of Japanese beetles. Birds can also be used as a preventative measure against other types of pests.
The best way to ensure the birds eat the Japanese beetles is to spray your infected ground with the mixture of soap and water mentioned above. This will attract the adult beetles to the surface. Then the birds will snap them up. You’ll want to start this cycle in late spring and repeat in fall until you no longer see the larvae in the soil.
8. Set Traps
You can use traps to lure male beetles away from your crops before they mate. The way most traps work is that an attractive scent is placed into a device that makes it impossible for the insect to exit. Then they’re starved. A pheromone works best as the attractant.
9. Use Row Covers
Row covers are a popular device used to prevent multiple types of pest infestations. This is one of the best recommendations for prevention. Row covers work by covering plants. They’re made in such a way that they prevent invasive pest species, while still allowing air, sun, and precipitation in. This way the plants can continue to grow, while also keeping out pests. You’ll want to utilize row covers in the summer, which is the peak time for Japanese beetle infestation.
Row covers come in different sizes and lengths and can cover entire plants. You’ll want to make sure to keep the cover edges flush with the ground, to ensure there are no gaps for beetles and grubs to escape through. Row covers will only work as a preventative measure – if the beetles have already infested your garden, it’s too late and you’ll need to try one of the other methods listed.
10. Use Drop Cloths
Another cover method is to use drop cloths. Plants can be covered with large drop cloths at night. Remove the cloths in the morning when the beetles are active and attached to the cloths. You can safely kill the beetles using the solution of soap and water.
11. Strategize Your Garden
Having a strong strategy around the crops you grow is also a natural and easy way to prevent a Japanese beetle infestation. Japanese beetles especially love apples, stonefruits, asparagus, corn, beans, shade trees, geraniums, grapevines, hibiscus, raspberries, and roses. Limit these attractive feasts in your garden or strategize where and how to plant them to limit their exposure to the beetles, while also maximizing a strategy for removal.
Now that you’re well-versed in how to prevent an infestation of Japanese beetles, you can use your newfound knowledge to keep them away! Keeping them away is always better than trying to remove them later.