One of the worst garden pest, the Japanese beetle feeds on a wide variety of plants. In fact, they survive and thrive eating more than 275 different types of grasses, ornamental plants, vegetables and fruit trees.
Throughout their lifecycle, Japanese beetles cause devastation to plants. In the grub phase, they devour plant roots. Additionally, the fact that the grubs make very tasty fair for a wide variety of animals such as, possums, skunks, and other carnivorous and omnivorous mammals adds the secondary threat of destructive digging in your yard, garden, field or orchard.
When the larva transform and emerge from the ground as beetles, they set to work right away consuming the foliage of almost any plants they happen to come in contact with.
It’s easy to see that these extremely hardy beetles present a real threat to the garden, but what can you do? In this article, we will describe Japanese beetles and discuss some organic methods you can use to deter and/or eliminate them. Read on to learn more.
What Do Japanese Beetles Look Like?
Mature Japanese beetles measure about a half-inch long, two-tone with an iridescent green front section and coppery bronze wings. They have small white tufts on their sides and also at the tip of the abdomen.
Generally fat and white, Japanese beetle grubs lay dormant about nine inches underground throughout the winter. In the spring, when weather begins to warm these lawn grubs move closer to the surface and begin eating the roots of plants.
In late spring/early summer (May through June) they emerge from the ground as adult beetles. At this point, they take the next 4-6 weeks of their life to wreak havoc on plant life and reproduce. They’ll spend the first 30 days of this time pretty much eating everything in sight! In the late summer and early fall, the females will lay eggs continuously until the first frost which signals their demise.
Japanese Beetle Control An Ongoing Task
It’s easy to see that your approach to controlling these beetles must be multi-pronged. It’s necessary to control both the grubs and the adults to make any headway at all. Additionally, you should know, you will never be rid of them. Even if you were to kill off every single grub and beetle on your property, others would come the next year. Work on controlling them (rather than eradicating them) as the best and most realistic goal.
Your control methods will to change from season-to-season as the beetle’s form changes. Several products and tactics have shown good results.
Boost The Health of Your Soil
Just as with all living things, healthy soil helps deflect pests and disease better than impoverished soil. Amend your soil for optimum health. The regular addition of humus and organic compost will help improve the overall health and bioactivity of your soil. This works to help keep plant roots healthy and strong so they can deflect pests. Grubs do not go after strong, healthy roots.
Reduce the Number of Grubs Naturally
It makes good sense to take steps for reducing the number of immature beetles while they hide in the ground. Early in the spring when feeding begins, apply an application of Bacillus papillae known as “milky spore powder.”
This type of bacillus specifically kills Japanese beetle grubs. To use it, you simply apply it to the soil of your yard or garden early in the spring. Follow up with an even watering to help the powder soak into the soil.
The grubs eat the bacillus spores and will die within three weeks time. When the grub dies, it releases more spores affecting other grubs.
This “natural” living organism form of pest control, continues to spread and effect the grub population for years on end. In warm climates apply the “milky spores” consistently for at least three years in a row and as many as five years in a row in cool climates.
With no negative effect on ornamental or food plants, no danger to humans, pets or native flora and fauna, this makes it a safe, natural deterrent for every type of crop. Only the Japanese beetle grubs find it lethal.
You can look for this garden product at home improvement centers and nurseries, or you can order Milky Spores online from Amazon.
Water With Beneficial Nematodes
You can improve the performance of “milky spores” by including beneficial nematodes in the water you use immediately after application of the bacillus. These microscopic insect parasites attach to larva and pupa found in the soil. These organisms (actually non-segmented roundworms) naturally occur in soil all over the world.
You can safely add nematodes to your lawn and garden environment. It carries no negative effect on any form of living creature other than the insect pests in a larval stage. In addition to being effective against Japanese beetles, you’ll find these beneficial nematodes also effective against:
- Colorado Potato Beetles
- Oriental Root Weevils
- Cucumber Beetles
- Asparagus Beetles
- Oriental Beetles
- Carrot Weevils
- Citrus Weevils
- June Bugs
The nematodes actually act very fast. Once applied to the soil via watering, they get busy seeking out pests to inhabit. When they find a pest, they enter it’s body and release a form of symbiotic bacteria that kills the pest off.
For best results apply beneficial nematodes early in the spring after all danger of frost passes. Just apply Milky Spore to the soil of your lawn and garden, and then follow it up with a watering treated with beneficial nematodes. Repeat this process after six months time passes. This will help boost your nematode population and spread your backfill is even more effectively.
You can find this product at your local lawn and garden center or purchase a product called NemaSeek Hb.
Keep Adult Beetles Under Control
Applying Bacillus popillae and enlisting the assistance of beneficial nematodes should reduce your grub population significantly. A few hardy adult beetles will surely emerge from the soil in the springtime intent upon consuming your flowers, vegetables and trees. To discourage them, apply a natural neem oil product generously.
You can buy natural neem oil intended for garden use quite affordably at your local garden center. Make an effective spray easily. Remember that with all-natural spray such as this, you must spray on a regular basis – especially after a rain.
Begin with a stronger concentration of spray (2 %) to kill off as many existing beetles as you can. Follow that up with a weaker mixture for prevention. ALWAYS TEST a small area for any potential reactions to plants before applying on larger spaces.
For a strong 2% solution try this recipe:
- Four Teaspoons of Pure, Cold Pressed Neem Oil
- One Third of a Teaspoon of Insecticidal Soap
- One Quart of Warm Water
Mix the insecticidal soap with the warm water. Add the neem oil slowly and stir well. Fill your sprayer with the mixture and use right away. Shake the solution from time to time throughout the application to make certain the neem oil stays mixed with water.
You can make bigger batches than this; however, remember it’s best for the mixture to remain at a warm room temperature for even disbursal of the oil. Use the entire mixture within 8 hours of preparation.
Make A Stronger Or Weaker Solution
Simply reduce the amount of neem oil by half to create a 1% solution. Half that to create a .5% solution. If you don’t have insecticidal soap on hand, you can use another type of detergent (e.g. dish soap). Additionally, you can make the batch more concentrated by doubling the amount of soap or detergent.
Spray Thoroughly & Frequently
When you apply the neem oil mixture, make sure to completely cover all surfaces of leaves and plants, especially the undersides of the leaves where insects love to hide. Drenching the soil surrounding your plants is also a good idea (and a good way to use up leftover solution if you make a big batch). Neem oil benefits the soil and will help prevent insects climbing up on your plants from the ground.
Generally speaking, you should begin the spring growing season with a strong application and keep a close eye on your yard and garden. If you see the signs of insect predation, go ahead and make another application. You may want to make it stronger and remember to apply a fresh dose after rain.
Even with all of your treatments, a few individual Japanese beetles will show up from time to time. This is especially true in very warm weather when with still air in the early morning hours. When you see individual Japanese beetles, pick them off by hand and plunge them into a bucket of soapy water. This will kill them and eliminate the scent of their pheromones which attracts other beetles.
Choose Unappetizing Plants
Although difficult, finding plants the Japanese beetles does not like, is possible. Here’s a few good choices:
Benefit From Complementary Planting
Japanese beetles find marigolds quite attractive. Lure them away from your preferred plants by planting a cheery, attractive border of marigolds around your ornamental and veggie gardens. Marigolds come in an attractive array of shades and sizes and can add both beauty and protection to your garden setting.
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