Japanese beetles are among the most common grass pests. They are harmful to all gardens, as adult specimens can eat the leaves and flowers of many types of plants. The larvae, known as white grubs, feed on the roots of plants and can create clods of dead grass. Adult beetles are metallic green in colour, and when they emerge from the ground in late spring or early summer, they immediately begin feeding on your plants. Knowing how to eliminate them effectively and efficiently can help prevent your beloved garden from becoming food for these insects.
Remove Japanese Beetles with Biological or Chemical Means
- Use nematodes to kill the larvae. These roundworms eat insects and feed on the larvae in the earth, becoming a natural control system against parasites. The most common nematode species include Steinernema feltiae and Heterorhabditis bacteriophora. Place them in the ground in late August or early September to start fighting next year’s maggots. However, you can apply this remedy as soon as you notice signs of Japanese beetle activity in your garden.
- Make sure you buy fresh roundworms, as they are living organisms. Water the soil before spreading them and keep it moist after applying the treatment. You can add these worms to mulch as well. For mixes of 50 or 100 million nematodes, use half a teaspoon for every 5 litres of water.
- Beneficial nematodes only attack soil-occupying pests, such as Japanese beetles, fleas, German cockroaches, termites, and ants. They are not harmful to people, animals, plants or earthworms.
- You can buy nematodes online, at garden centres, or major home improvement stores.
- This method is effective in eliminating parasites in the larval stage.
2. Chemically eliminate the larvae with an insecticide. You can spray the plants with a specific product against Japanese beetles, which you can find in many shops and on the internet. Carbaryl powder can work too, but it can kill beneficial insects as well as Japanese beetles.
- Some ingredients to look out for when buying an insecticide are carbaryl, acephate, and permethrin. Pyrethrin products are a safe way to control pests on plants and get rid of other beetles at the same time.
- Some insecticides are thought for high Japanese beetle activity in the garden. Others are designed to be used in early fall when the eggs have hatched and the larvae are present. Be sure to read the treatment label before purchasing, so you can find out which specific problem it is best suited for.
3. Use organic neem-based insecticides. Neem oil is a natural pesticide that comes from the seeds of the tree of the same name and is an excellent deterrent, capable of keeping Japanese beetles away from plants. Spray it on the latter to keep the pest population in check.
- Azadirachtin, one of the substances that make up neem oil, also acts as a repellent for nematodes and pushes them not to eat plants. Be careful with this treatment if you have added nematodes to the soil to fight the larvae.
- You can purchase neem oil-based insecticides on the internet and at gardening stores.
4. Spray insecticidal soap on Japanese beetles. Sprays of this type are contact pesticides, with no residual effect. They are similar to household cleaners but are specifically designed not to be harmful to plants.
- When you apply insecticidal soap, you need to wet the pests completely. You will need to reapply for the treatment every 4-7 days.
- These sprays must contain potassium bicarbonate.
- Even soaps designed specifically against insects can harm some plants. Check the label on the package or test a plant before applying the treatment to the entire garden.
Eliminate Japanese Beetles with Other Methods
1. Detach adult Japanese beetles from your plants. You can easily remove these insects with your hands. Once they are taken, throw them in a bucket of soapy water.
- Avoid crushing the beetles to kill them. These insects attract their kind with pheromones so powerful that they can draw specimens from hundreds of meters away. By squeezing one, you risk releasing the female beetles’ sex pheromone.
- You should take care of the pest control early in the morning. Spread a towel on the ground and shake the plants, then toss the beetles into the soapy water.
2. Choose your plants carefully. Japanese beetles are attracted to some species, so when designing your garden, avoid the plants that attract them. Carefully consult the list of the most vulnerable varieties; you can find them easily on the internet.
3. Repair plants with movable covers. These sheets let in sunlight, air and water, but not the beetles. Make sure the edges are snug against the ground so insects can’t crawl underneath. If you already have a maggot problem, avoid this solution which could trap the beetles inside the cover along with the plants.
- You can buy covers of this type on the internet or in garden stores.
4. Keep plants healthy. Japanese beetles are attracted to very ripe and rotten fruit. To avoid attracting them, do regular crops and try to keep the plants healthy.
5. Avoid traps for Japanese beetles. These systems use pheromones and scented baits to attract insects. Many studies have found that they attract more beetles than they trap. This means that the insect population in your garden would increase, exacerbating the problem. Use this method only if you have a large plot of land and can place the trap a good distance from the garden.
- Place a glass jar in the garden that contains a few inches of apple cider vinegar. If you wish, you can add some sugar. Make sure the opening is large enough for the beetles to enter, which will fly into the liquid and drown.
- The best way to keep these pests under control is to design a system that includes the prevention of larval growth, the capture of adult specimens and avoiding the presence of plants vulnerable to infestations.
- Some Japanese beetle resistant plants include red maples, dogwood, lilac, holly, pine, hickory, and juniper. The species vulnerable to infestations include apple, cherry, oak, birch, willow and black walnut.