Adult beetles live 30 to 45 days and feed voraciously.4 They tend to gather to feed and lay eggs. During a two- to three-week period, female beetles repeatedly tunnel a few inches into the ground and lay up to 60 eggs each.3 Areas of healthy, sunny, well-irrigated and well-maintained lawn grasses are prime targets.
Japanese beetle eggs hatch during midsummer. The immature larvae, or grubs, stay close to the soil's surface and feed on grass roots. The grubs pass through several stages during growth, each one more damaging than the first. By the final stage, the plump, semi-transparent larvae measure about 1 inch long. Damage shows up in mid-to-late summer, as random lawn patches turn brown and die. The rootless turf rolls back easily, like a loose household rug, exposing grubs curled into a classic "C" shape.
As cool fall temps arrive, grubs move deeper into the soil, where they're protected from winter extremes — and efficient treatment. When spring returns, grubs move back toward the soil surface and feed until late spring. Then they change into a non-feeding stage called pupae. Mature beetles emerge in about two weeks, and the destructive cycle starts over again.3
Controlling Japanese beetles involves treating the separate life stages. Proper products and timing strike the beetles and their larvae at their most vulnerable. Pesticides with proven beetle-fighting ingredients, such as those in Sevin® garden insecticides, provide effective control of Japanese beetles in the adult stage and as grubs.
- For mature beetles — Take a proactive approach with Sevin® Insect Killer, available in ready-to-use, concentrate and ready-to-spray forms, or Sevin®-5 Ready-To-Use 5% Dust. Early, diligent treatment prevents plant damage and grub-producing eggs. Follow label instructions for your chosen product, including time allowed between application and edible harvests. When using liquid Sevin® Insect Killer products, for example, leave a pre-harvest interval (PHI) of one day between treatment and harvest of raspberries or blackberries – two Japanese beetle favorites. If treating these caneberries with Sevin®-5 Ready-To-Use Dust, allow a seven-day PHI.
- For grubs — Get maximum impact by treating in mid-to-late summer, when grubs are newly hatched, small and actively feeding near the surface.3 Apply Sevin® Insect Killer Granules according to label instructions, and water well to release treatment into the soil where grubs dwell. Treat again in early spring, when overwintering grubs move back near the surface, before they pupate and emerge in beetle form. Check the label for PHIs on any edibles in your landscape. Give raspberries three days between application and harvest when treating with Sevin® Insect Killer granules. Like liquid Sevin® Insect Killer insecticides, these granules kill Japanese beetles and their grubs by contact. Then they continue protecting your landscape for up to three months.
Proper treatment and timing helps stem the tide of Japanese beetles in your garden and across the United States. With effective Japanese beetle control from GardenTech® brands and Sevin® insecticides, you can take on these troublesome invasive pests and win.
Always read product labels thoroughly and follow instructions, including guidelines for pre-harvest intervals (PHI) and application frequency.
GardenTech is a registered trademark of Gulfstream Home & Garden, Inc.
Sevin is a registered trademark of Tessenderlo Kerley, Inc.
1. U.S. Department of Agriculture Animal and Plant Health Inspection Service, “Managing the Japanese Beetle: A Homeowner's Handbook,", U.S. Department of Agriculture, August 2015.
2. U.S. Department of Agriculture Animal and Plant Health Inspection Service, “Japanese Beetle Predicted Development Stages," U.S. Department of Agriculture, July 2015.
3. New York State Integrated Pest Management Program, "Grubs in Your Lawn? A Guide for Lawn Care Professionals and Homeowners, Cornell University.
4. M.F. Potter, D.A. Potter and L.H. Townsend, “Japanese Beetles in the Urban Landscape,"University of Kentucky College of Agriculture, January 2006.