Every gardener fears that time of year that the Japanese beetle enters the garden space. In the past, control was based on synthetic pesticides that had limited success. But today the gardener has many different choices of organic control methods to choose from.
One control method used by some gardeners is to avoid planting plants that the Japanese beetle loves. This includes apple and maple trees, grapes, roses, irises, basil, Echinacea, dahlias, cosmos, hydrangeas, zinnias, rhododendrons, and wisteria.
Japanese Beetle Traps
These traps were designed a few years ago to attract the Japanese beetle to the trap using a sexually based hormone. While this does attract and trap beetles, some feel that it invites more beetles then would normally be attracted to the environment.
There are two approaches to a trap’s use. The first approach consists of hanging the trap where the beetles have been seen. The other approach is to hang the trap away from sensitive plants that the beetles are feeding on. The basic theory of this approach is that the beetles will be lured away from these plants with the smell of sex.
Japanese beetles are easily removed by hand. They can simply be removed by sucking them up with a vacuum cleaner. If this approach is used, remember to empty the vacuum cleaner before storing it away. If there are only a few beetles, simply pick off by hand and destroy. If there are several beetles, merely knock them off into a bucket of warm, soapy water. The beetles can be easily dislodged by with the hand or knock off with a long-handled tool such as a spatula, spoon or broom.
Another approach to controlling these beetles is through companion plantings. Garlic and chives planted around plants will deter beetles from the area by their smell. But for this to work correctly, the plants need to be encircled by the garlic and/or chives plantings.
Milky spore is a bacterium that is placed around plants. The beetles eat this bacterium and die. Once dead, the bacterium is re-released into the environment and the process starts all over.
Homemade sprays are easy to make with common household ingredients. There does exist two forms of homemade spray. The first type makes the plant material distasteful for the Japanese beetle. The second type of homemade spray will kill the Japanese beetle when it is consumed.
Homemade Spray-Repellant Form
The first kind of spray requires cayenne pepper, organic liquid soap, water and a spray bottle. Mix a little cayenne pepper and liquid dish soap together and thin out with water. Place the mixture in a spray bottle and apply to effected foliage.
The second type of spray uses apple cider vinegar. To make this spray, mix one part apple cider vinegar with one part water. Place liquid in a spray bottle and apply as needed.
Homemade Spray-Japanese Beetle Pesticide
This spray is made from plant material that the gardener may have growing in their yard. These plants are the larkspur and the delphinium. Both of these plants contain poisonous chemicals that when eaten kill Japanese beetles.
To make this spray, collect a handful of larkspur and/or delphinium leaves and place in an old blender. Avoid using your good blender for this project. To the pureed leaves, add a gallon of water and blend well. Place mixture into a spray bottle and apply to the foliage being eaten by the beetles.
While these approaches will help control the Japanese beetle there are also some helpful hints that need to be considered before utilizing any of these techniques. First, know your insects. Many gardeners have mistaken harmful insects for beneficial ones. Make sure you have a Japanese beetle infestation before applying anything. Second, only apply these techniques in the morning. The beetles are slower in the morning, which makes manual removal easier. Also applying the spray in the morning will reduce foliage burn. Third, when applying any of these sprays always wear gloves and goggles. Finally, when making sprays that require “soap” only use “soap” and not detergent. “Soap” will not burn the plant material compared to detergent.