Learn more about their life cycles and when to use pest control products.
FAQ: What are the best times to control grubs and Japanese beetles?
It's a vicious cycle... Grubs turn into Japanese beetles and these beetles produce more grubs. The life cycle of the Japanese beetle takes approximately one year from egg to adult. This combination of grub and mature beetle dishes out a double threat to homeowners and gardeners during the warmer months. While the grub larvae feed on the roots of our lawns, the adult Japanese beetles turn foliage and flowers into lace, as they nibble voraciously into June, July and August.
Life Cycle of the Japanese beetle: From egg to adult
- In summer, females leave the plants and burrow about three inches into the ground to lay a few eggs at a time. One female might lay a total of 40 to 60 eggs.
- The eggs hatch in mid-summer and the grubs begin to feed. In late autumn, the grubs burrow 4-8 inches into the soil. They spend 10 months of the year in the ground. They are about an inch long when fully mature.
- In early spring, the grubs return to the turf and feed on roots until late spring, and change into pupae. After two weeks, the pupae become beetles and emerge from the ground. —U.S. Department of Agriculture
What products can you use to control grubs?
Bayer Season Long Grub Control: Traditional formula kills grubs all season long. Apply once anytime, spring through late summer.
Milky Spore Granular Grub Control: The natural bacteria in Milky Spore powder kills Japanese beetle larvae (white grubs) that live in the soil and feed on grass roots. When you apply the powder to your lawn to kill the initial grubs, the spores actually multiply in the soil, remaining viable for many years. Milky Spore can be applied anytime that the soil is warm.
How do you control Japanese beetles?
Captain Jack’s Dead Bug Brew: The organic chemical spinosad, a natural bacterial toxin, kills Japanese Beetles as well as caterpillars, thrips, spider mites and a host of other destructive plant pests. Spray foliage. (Follow directions on product label.)
Neem Oil: The organic, natural pesticide derived from Neem trees is another organic option. Neem oil acts as a repellent that makes the plant sprayed less attractive to hungry Japanese beetles.
As a Preventative: By applying the Milky Spore powder, it helps to reduce the number of Japanese beetles for the next season. Only one application is necessary.
Japanese Beetle Traps: Beetle traps have an attractant that lures Japanese beetles. Place traps a good distance away from your garden or plants that you want to protect, or you will end up attracting more beetles than you had before. The best scenario is to use them at the perimeter of a large space (not a small space), so traps will capture these pesky bugs and draw them away from the garden.
Best Times to Control Grubs and Japanese Beetles (See chart)
Apply in April-May-June for moderate control.
- Grubs rise to soil’s surface to feed on grass roots. - Pupa forms - Adult beetle emerges. Apply in July-August-September for optimum control. - Beetles lay eggs. - Grubs hatch and feed on grass roots. - Grubs grow rapidly.
October-November-December
-Grubs return to their winter depth in the soil.
