Here at EcoTurf we do not treat or deal with adult Japanese Beetles, we treat them at the grub stage, and also know it is important to talk about the entire insect and some creative ways to make your landscape less appealing to these little buggers. By having an integrated pest management strategy, success will be greater than putting all your eggs in one basket.
The goal is not complete 100% removal but suppression of grubs and adults. We want a landscape that is less attractive to adults to lay their eggs in which helps reduce the damage caused by the grubs and adults!
Grubs – we apply a preventative turf application early in the season which is systemic and less harsh on native insects present than rescue treatments applied later in the year if grubs are discovered and damage already occurred. Because we all can’t be like Palisade, Colorado and get 100% homeowner buy-in for applying insecticides, we encourage the preventative application because it is lower in toxicity. There is increased spread of grubs in Northern Colorado – Greeley, Windsor, Johnstown, and Fort Collins all have neighborhoods where Japanese Beetle populations are established. Here is more info about the grubs specifically. https://myecoturf.com/lawn-problems-grubs/
If you are building a new house or planning do some re-landscaping here are some things you can do. Use rocks instead of mulch at least 3 inches deep since the Japanese beetles burrow down 3 inches to lay their eggs. Using rocks instead of cedar mulch, around your ornamentals, is one method in an Integrated Pest Management Program to reduce the number of Japanese adults and therefor grubs in your yard.
Plant trees, shrubs and flowering plants the Japanese Beetles do not prefer to feed on. Diversification is key too – planting a variety of plants helps make your landscape less attractive. If you have a rose garden, you are putting up a neon sign to the beetles to come to your landscape. Removing roses and replacing with several Japanese Beetle resistant plants would be better than planting one variety.
These plants are what the Japanese Beetles love to feast on. Avoid these.
| Crabapple, apple | Roses |
| Norway & Japanese maple | Grape Vine |
| American elm | Virginia Creeper |
| American linden | Hollyhocks |
| American mountain-ash | Dahlia |
| Horsechestnut | |
| Plum, Cherry, Peach, Apricot, | Hibiscus |
| Pin Oak | Peony |
Alternatives Japanse Beetle Resistant
| Red Maple | Columbine |
| Redbud | Coreopsis |
| Hickory Tree | California poppy |
| Magnolia | Hydrangea |
| Kentucky Coffee | Rubeckia |
| Spruce | Lilac |
| Pine | Impatiens |
| Boxwood | Sedum |
| Burning Bush | Violet, pansy |
| Northern Red Oak | Foxglove |
The above list is small – Japanese Beetles eat 350 known varieties! A local project in Douglas county CSU Extension is involving the public on observing plants and noting damage. This is a large and amazing resource for homeowners and landscapers should utilize for their customers as well.
Annual Flowering Plants List
https://douglas.extension.colostate.edu/wp-content/uploads/sites/50/2022/12/2023-Annuals.pdf
Perennial List
https://douglas.extension.colostate.edu/wp-content/uploads/sites/50/2022/12/2023-Perennials.pdf
Trees and Shrubs List
In regards to traps, studies have shown the pheromones in the traps will attract more beetles from miles away. Traps are best to use for a few hours to assess the infestation population. Traps were used in Palisade each year to assess Japanese Beetle populations but not as a method to try and reduce the number present. See below articles for more info about why traps are not recommended.
CSU article – “Repeated trials have demonstrated that use of such traps does not reduce the number of beetles damaging nearby vegetation. Furthermore, the use of Japanese beetle traps often increases damage by Japanese beetles by drawing into the vicinity larger numbers of beetles than are captured in the traps. Because of this Japanese beetle traps are not recommended for Japanese beetle control.” https://extension.colostate.edu/topic-areas/insects/japanese-beetle-5-601/
Here is an excerpt from a University of Minnesota article – “It is estimated that only 75% of beetles attracted to a trap end up in the trap, so in the end, you can be drawing large numbers of Japanese beetles to your area, while only capturing some of them. Studies have shown that traps lead to more plant damage in the areas they are placed. One study found that a trap placed alone led to nearby vegetation having more damage than in similar areas where no traps were placed.” https://extension.umn.edu/yard-and-garden-news/dont-fall-japanese-beetle-trapping-trap
We recommend rock around ornamental plantings, preventative grub application in turf for known established Japanese Beetle population areas, planting Japanese Beetle resistant trees, shrubs and flowering plants to make your landscape less appealing – all 3 of these working together will help to suppress the adults and grubs and make your landscape not as Japanese Beetle friendly.
