Japanese Beetles

Information taken from Ohioline fact sheet - HYG-2504-91

To view fact sheet - http://ohioline.osu.edu/hyg-fact/2000/2504.html

To view fact sheet on control of Japanese Beetles and Grubs - http://ohioline.osu.edu/hyg-fact/2000/2001.html

 Photos from:
       University of Kentucky Department of Entomology  &  USDA Animal and Plant Health Inspection Service
Managing Adult Japanese Beetle                                  Managing the Japanese Beetle

Damage Symptoms

The adults are skeletonizers, that is, they eat the leaf tissue between the leaf veins but leave the veins behind. Attacked leaves look like lace that soon withers and dies. The adults will often attack flower buds and fruit. The grubs can kill small seedling plants but most commonly damage turf. The turf first appears off-color as if under water stress. Irrigating causes a short-lasting response or no response at all. The turf feels spongy under foot and can be easily pulled back like old carpet to reveal the grubs. Large populations of grubs kill the turf in irregular patches.

Control Strategies

See: White Grubs in Turfgrass (HYG-2500). Since this pest is important in agriculture and commerce, considerable effort has been placed on developing control options.

Option 1: Cultural Control - Quarantine - Japanese beetle quarantines are currently operated by the USDA-APHIS and states involved with shipping materials out of infested areas to uninfested areas. Though this has not stopped the slow progression of Japanese beetles westward, it seems to have slowed the process. Nurserymen and sod producers shipping plant material with soil out of Japanese beetle infested areas must obtain an inspection and certification. Often, airports and rail yards are under quarantine and transporters must treat their containers before shipping.

Option 2: Cultural Control - Habitat Modification - Since the eggs and young grubs are very susceptible to dry soils, do not irrigate during the time the eggs and first instar larvae are developing. However, if natural rainfall occurs, this tactic will not work. Do not plant trees and shrubs that are highly attractive to adult Japanese beetles near turf. This is especially true along golf course fairways. Trees and shrubs most attractive to adults include: Japanese and Norway maple, birch, pin oak, horse chestnut, rose of sharon, sycamore, ornamental apple, plum, cherry, rose, mountain ash, willows, lindens, elms and Virginia creeper. Trees and shrubs rarely attacked include: red and silver maple, holly, boxwood, euonymus, flowering dogwood, cedar, juniper, arborvitae, red oak, tulip tree, magnolias, red mulberry, forsythia, ashes, privet, lilac, spruces, hydrangeas and taxus (yew).

Option 3: - Biological Controls - Insect Parasites - Several parasitic wasps, especially Tiphia popilliavora and T. vernalis, and the winsome fly, Hyperecteina aldrichi have been imported and are now known to be established in several eastern states. Unfortunately, these parasites do not seem to be reliable in reducing Japanese beetle populations below damaging levels. However, the Tiphia appear to be more efficient in southern states.

Option 4: Biological Control - Bacterial Milky Disease - The bacterial milky diseases, Bacillus popilliae Dutky and B. lentimorbus Dutky, have been quite effective at controlling grubs in certain areas of the eastern United States. The spore count must build up for 2 to 3 years to be very effective. During this time you should not use an insecticide against grubs that are needed to complete the bacterium cycle. There is some recent data that suggests that these bacterial diseases may not be performing well in certain areas. This may be due to reduced virulence, soil conditions or grub resistance. More commonly, different white grub species have displaced the Japanese beetle grubs. In Ohio and Kentucky, test trials have not produced satisfactory results. Additional experiments are needed to determine the lack of efficacy of milky disease in these soils.

Option 5: Biological Control - Entomophagous Nematodes - The insect parasitic nematode, Steinernema (=Neoaplectana) glaseri Steiner, was used before 1940 and had considerable promise but this agent was not developed further because of problems of rearing and expense. This nematode may be economically available in the future. Commercially available products containing strains of S. carpocapsae have been marginally effective. Preparations containing Heterorhabditis spp. seem to be the most effective of the currently available nematodes. Apply the nematodes when the white grubs are in the second instars. Irrigation before and after nematode application with 1/4 inch of water minimum greatly increases the efficacy of the nematodes.

Option 6: Mechanical Control - Trapping - Several traps have been developed to capture the adults. These traps generally use a mixture of the aggregation and sex pheromones. Recent data indicate that these traps do not significantly reduce grub populations and in some cases may actually contribute to increased foliar plant damage. There has been no correlation between trap captures and reductions in white grub populations in surrounding turfgrass areas.

Option 7: Chemical Controls - Insecticides - Consult, HYG-- 2500,White Grubs in Turfgrass for insecticide use recommendations. Bulletin L-187 lists the pesticides currently registered. When using trapping to monitor adult activity, keep in mind that the females lay the majority of their eggs within the first 7 to 10 days of their existence. They may live considerably longer than this and could be trapped into September and October. Usually, in Ohio the majority of Japanese beetle eggs have been laid by the end of the first week of August.