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Adult Japanese Beetles Arrive Early

The first adult Japanese beetle confirmed for 2012 was on May 24 in Indianapolis (46201). This is consistent with a weather-based model that predicted first beetle emergence on May 20, 2012. Check for Japanese beetles now.

  • Japanese Beetle - Photo Credit: Steve MayerFirst Japanese beetle adult found in central Marion County, IN (46208), on the same site in recent years:
  • 2004 - June 9 (from a nearby site)
  • 2005 - June 15
  • 2006 - June 16 (June 2 on north side of Indianapolis)
  • 2007 - June 8 (June 3 in other locations in central Indiana)
  • 2008 - June 25 (June 13 in West Lafayette & June 20 in Franklin, IN)
  • 2009 - None documented (June 22 at another site in Indianapolis)
  • 2010 - None documented (June 14 in Hamilton County) 
  • 2011 - June 29 (June 9 in northern Marion County, June 18 near Holliday Park, weather data model predicted a June 11 first emergence date)
  • 2012 - None documented yet (May 24 in 46201 zip code)

 

To control adult Japanese beetles, consider the following suggestions on this page.

For preventative treatments of grubs in the lawn, apply products containing imidacloprid or halofenozide before eggs hatch (late July-early August). Curative grub treatments are applied in August after egg hatch.

Japanese Beetles: What Works & What Doesn't

What Works

Use Resistant Plants: When planning your landscape, choose plants which show resistance to Japanese beetle. This is the easiest, most effective and most environmentally friendly way to control these pests. Two Purdue Extension publications are available which provide lists of susceptible and resistant plants: E-75 (Japanese Beetles in the Urban Landscape) and ID-217 (Crabapples Resistant to Apple Scab and Japanese Beetle in Indiana).

Monitor Preferred Plants Early to Detect Japanese Beetles: Monitor linden trees, smartweed or other preferred plants to detect Japanese beetle presence. If you pick off the beetles as they arrive and remove the initial damaged foliage, you will remove signals that can attract other beetles.

Physical Removal: You can remove adult Japanese beetles by hand if your planting is small and beetle numbers are relatively low. The beetles can be killed by causing them to drop into a container of soapy water. With the container opening under the beetle, poke at the beetle. It will readily fall into the container and die. This may be easier to do early in the morning when temperatures are lower because the insects are more sluggish.

Exclusion: Small plants such as roses (or parts of plants) can be protected by covering them with cheesecloth or other fine netting (less than one quarter inch) during peak beetle activity. Make sure no openings exist that can allow the Japanese beetles to enter.

Insecticides: See Purdue fact sheet E-75 for recommended insecticides for the control of adult Japanese beetles in Indiana. 

Soil applications of imidacloprid or acetamiprid can reduce the amount of defoliation caused by adults when applied to soil at the base of a tree. However, applications to the soil are needed before the beetles arrive (usually a late May treatment) to give time for the trees to take up the materials into the leaves. For a non-chemical alternative, try using "Neem" products containing Azadirachtin (NOT the same as Neem Oil). They may be effective as a repellant that can reduce defoliation when applied regularly during beetle flight. You must apply them before defoliation becomes intolerable. Some entomologists suggest Azadirachtin is most effective when applied just before the beetles emerge. Consult Kentucky Extension publication EF451 for additional comments on botanical alternatives.

Use of Trap Plants? Some people have had success using trap plants (unwanted preferred plants, e.g. smartweed and others) to draw the beetles away from other desired plants. However, this could also draw more beetles into the area.

What Doesn't Work

Avoid Japanese Beetle Traps: There is no doubt that Japanese beetle traps catch large numbers of beetles. However, they usually do not reduce damage to plantings. Research has shown that these traps attract many more beetles than are caught. Therefore, susceptible plants along the flight path of the beetles and in the vicinity of the traps are likely to suffer more severe damage than if no traps were used.

Grub Insecticides Do Not Solve Adult Beetle Problems: Insecticides can be applied to lawns at the proper time to effectively control the young Japanese beetle grubs and prevent damage to the lawn. However, this will not likely provide control of the adult beetles in residential areas since they can fly 1-2 miles to feed on the leaves of desirable plants.

Avoid Home Remedies: Sprays made from ground-up beetles, interplanting with supposedly repellent plants, and other home remedies have not been shown to be effective.

For More Information

Japanese Beetles in the Urban Landscape (Purdue) (Revised 2/2010)
Crabapples Resistant to Apple Scab and Japanese Beetle in Indiana (Purdue)
Japanese Beetle ID Card (USDA APHIS)
Japanese Beetles in the Urban Landscape (University of Kentucky) (Rev 1/2006)
Control of Japanese Beetle Adults and Grubs in Home Lawns (Ohio State)
Managing the Japanese Beetle: A Homeowners Handbook (USDA)
Japanese Beetle Program (USDA APHIS)
Japanese Beetle Program Manual for Airports (USDA APHIS) (130 pages)
Relative Susceptibility of Woody Landscape Plants to Japanese Beetle (ISA Journal of Arboriculture)

Updated 5/2012