Starting in late June, just as the garden is at its peak, an unwelcome visitor often makes an appearance: the Japanese beetle. This voracious pest can cause significant damage by attacking over 300 species of plants. Fortunately, effective strategies and products exist to help you regain control and protect your garden.
The Two-Front Battle: Grubs and Adults
To effectively control Japanese beetles, you must understand that the fight takes place on two fronts:
- Below Ground: against its larvae (white grubs) that devour the roots of your lawn.
- On Your Plants: against the adult beetles that feed on foliage, flowers, and fruit.
By taking action on both fronts, you will break the insect's life cycle and achieve lasting results.
Step 1: Tackling the Larvae (White Grubs) in the Lawn
The problem begins long before you see the first beetle flying. The larvae, small "C"-shaped white grubs, spend the winter in the soil and actively feed on grass roots in the spring and autumn.
Signs of a Grub Infestation:
- Your lawn has yellowing patches that look dry, even after watering.
- The turf lifts easily, like a carpet, because the roots have been severed.
- Skunks, raccoons, or birds are digging up your lawn to feed on the grubs.
Biological Solutions for the Lawn
Two excellent biological options are available to eliminate grubs in the soil.
1. Grub B Gon Max Grub Killer
- How it works? When applied to the lawn, the product is ingested by the grubs. The bacteria, Bacillus thuringiensis galleriae (BtG), activate in their digestive system and stop them from feeding, leading to their elimination within a few days.
- When to apply? For maximum effectiveness, apply from late summer to early autumn when the new grubs are young and active. A spring application is also possible to control grubs that survived the winter.
- Benefits: This product is not harmful to bees, earthworms, pets, or wildlife.
2. Beneficial Nematodes
- How it works? Nematodes actively hunt for grubs in the soil, penetrate them, and release a bacterium that kills them from the inside within 24 to 48 hours. They then use the grub's body to reproduce, creating a new generation of nematodes to continue the fight.
- When to apply? Application is ideally done during the same period as Grub B Gon Max (late summer/early autumn). The soil must be moist and its temperature above 12°C. It is best to apply them in the evening or on a cloudy day to protect them from UV rays.
- Benefits: This is a 100% natural solution that is safe for the environment, humans, and animals.
Step 2: Controlling Adult Beetles on Plants
Once the larvae transform, the adult beetles emerge from the soil, usually from late June to late August, ready to devour your plants.
Recognizing the Adult:
The Japanese beetle is easy to identify. It is about 1 cm long and has a shiny, metallic green body and copper-coloured wing covers. Small tufts of white hair are visible along the sides of its abdomen.
Solutions for Protecting Your Plants:
1. Japanese Beetle Traps with Bait
These traps are a powerful tool for reducing adult populations. They use a dual-action bait: a floral lure to attract both males and females, and a sex pheromone to specifically attract males.
- Crucial Placement Tip: To avoid attracting beetles towards your precious plants, place traps at a distance of 10 to 15 metres (30-50 feet) away from the plants you want to protect. The goal is to intercept and draw them away from their targets. Empty the traps regularly.
2. Hand-Picking
Simple, free, and very effective for small infestations. Early in the morning, the beetles are sluggish from the cool air.
- Place a bucket of soapy water under the infested leaves.
- Gently shake the branches to make the insects fall into the water. They will not be able to escape.
Prevention Strategies for a Healthy Garden
The best defence is a garden that is less welcoming to Japanese beetles.
- Maintain a dense lawn: A healthy, thick lawn is more difficult for females to penetrate when looking to lay their eggs. Maintain a mowing height of 8 cm (3 inches) and water deeply but infrequently.
- Incorporate repellent plants: Think about adding plants like garlic, chives, Nepeta (catmint), tansy (Tanacetum) and scented geraniums.
- Monitor "magnet" plants: Roses, grapevines, hibiscus, and linden trees are particular favourites of Japanese beetles. Inspect them first and act at the first sign of damage.
The Key to Success: A Combined Approach
To get rid of Japanese beetles for good, persistence and an integrated approach are essential. By combining a lawn treatment for grubs using solutions like Grub B Gon Max or beneficial nematodes, with the use of traps and hand-picking for the adults, you attack the problem at its source and effectively protect your garden all season long.
For advice tailored to your situation and to get the right products, do not hesitate to consult our garden centre specialists. They will guide you toward the best solution.
