These include many significant horticultural and agricultural crops like corn, alfalfa, peaches, raspberries and roses. The damage appears as leaf skeletonization. Large numbers will congregate on single plants and decimate the foliage.

The larvae are white, “C”-shaped, and about an inch long. These are found in the root zone of turfgrass and other plants during late-summer. In the larval stage, Japanese beetle feeds on the root systems of cool-season grasses such as fescues, perennial rye and bluegrass. They tend to favor irrigated grasses in the arid west.

“The above ground damage from Japanese beetle larvae to turfgrasses can be hard to notice, but it’s there, and is typical of damage caused by other grubs that feed on turf root systems,” said Dr. Thaddeus Gourd. He’s a Colorado State University Extension Agricultural Agent for Adams County. “It takes a fair number of grubs to elicit a response above the ground.

“The population threshold is 10 grubs per square foot. In the northeastern United States, where Japanese beetle grubs have developed into a serious turf pest, skunks and raccoons are known to tear up the turf to feed on them, and cause further damage to turf and golf courses.”

It was previously thought Japanese beetle could not survive the harsh winters in Colorado high country or desert habitats of the lower elevations, but unfortunately, this is no longer the case. The Japanese larval habitat in Colorado is confined to the micro-environment defined by irrigated turf grass.

Japanese beetle is most commonly spread through the transportation of nursery plants. The larvae are in the soil surrounding the roots. Both the larvae and adults favor lush or well irrigated plants.

Emigrating Beetle

Japanese beetle is not native to North America or Colorado. It is said to have first arrived in New Jersey, via Japan, around 1916. Since then, having few natural predators, it has steadily migrated west, and is now a major pest in many Eastern and Midwestern states. In 2003, it was discovered in turf and plants in Palisade, Colo. Palisade is known for its peach orchards and wine vineyards and is located in Mesa County in western Colorado.

Palisade implemented an extensive eradication program involving a residential spraying plan. Bayer Environmental Science donated Merit insecticide for the town’s eradication program. The town is still challenged with eliminating this pest.

Then in 2005, Japanese beetle was located on a golf course in Denver. In 2007, it was found again on several other golf courses on Colorado’s Front Range. County, state, university and municipal parks and recreation organizations organized the Colorado Front Range Japanese Beetle Task Force, and initiated a delineation trapping program to discover exactly where the Japanese Beetles were located. The trapping continued through 2008 to find the density and distribution of this pest along the Front Range.

The traps are used to establish the area of infestation. They are constructed of green and yellow plastic with four vanes above a collecting container.

A floral-based lure that is attractive to both sexes is used. Some traps also include pheromones in order to draw more males to the trap. The trapping program is strictly for monitoring, and is not significant in stopping Japanese Beetle’s progression.

“The Colorado Front Range Japanese Beetle Task Force consisted of personnel from Colorado State University Extension in Adams, Arapahoe, Boulder, Douglas and Jefferson counties, Colorado Department of Agriculture, USDA-APHIS-PPQ, Jefferson County Weed and Pest Management Department, Colorado Green House and Nursery Association, and the Rocky Mountain Area Golf Course Superintendents Association,” said Gourd. “Also, Bob Hammon, CSU Extension from Mesa county was a key resource in this group.

“The Japanese Beetle Task Force objective for 2008 was to coordinate efforts in determining the distribution and potential movement of Japanese beetle and promote agency dialogue, while preventing the duplication of efforts. An online reporting system was created to enable the monitoring of recently trapped beetles promoting a rapid response to “hot spots” of new infestations.”

Winter Survival

Volunteers reporting online allowed researchers to plot beetle numbers during the trapping season. Utilizing Colorado State University Extension Master Gardeners, Nursery growers and superintendents as volunteers in setting up and monitoring these traps allowed the task force to save over $42,110 in wages and fuel.

The bottom line results in 2008 were that densities of beetles caught were greater in Arapahoe and Denver counties—highly urbanized areas adjacent to golf courses. Diminished numbers of beetles were caught with increasing distance from those high density population centers.

“Interagency cooperation/collaboration was instrumental in the success of the Japanese beetle monitoring program in the Front Range of Colorado,” Gourd said. Due to the ability of larvae to survive winter soil temperatures and emerge in the spring to continue development, control of Japanese Beetle can be a challenge, but Dr. Gourd notes this pest has great potential for an Integrated Pest Management (IPM) program.

Colorado State University Extension will be involved in the education of homeowners, private industry and government employees on chemical, mechanical, biological and cultural management options for the Japanese Beetle. “As for biological control methods, Bacillus popilliae, or milky spore disease, only kills the larvae, and the results have been disappointing in dry climates,” Gourd said.

“Ovavesicula popilliae, a protozoan that affects insect Malpighian tubes and hindgut is very promising in Michigan and Connecticut. Several Parasitic Wasps, Tiphia popilliavora and Tiphia vernalis, affect Japanese Beetle larvae. Tachinid, or Winsome Flies, affects the adults.

“Heterorhabditus zealandica X1 strain or H. bacteriophora GPS 11, a nematode, kills only the larvae. The nematodes should be applied when the white grubs are in the first and second instar—the middle of July in Colorado. Turf managers should irrigate before and after the nematode application with a minimum of a quarter-inch of water.” Again, use of nematodes for biological control in Colorado has provided poor results due to the low precipitation and an arid climate.

Cultural Management

According to Gourd, cultural practices to manage Japanese Beetle may involve habitat manipulation, or drying down the turfgrass. This means reducing the amount of water the turf receives at the time when the Japanese Beetle is laying eggs—beginning in late June.

The grub has numerous stages. At the first instar, it is very susceptible to drying out. Because the female lays egg throughout the summer the process must continue through July and August. Turf managers should water deeply every seven to 10 days, then let the soil dry out between irrigation. Japanese Beetle is less attracted to some types of turfgrass, and grass breeders are looking at producing Japanese Beetle tolerant cultivars in the future.

For 2009, the Front Range Japanese Beetle Task Force plans to continue its interagency cooperation and collaboration needs. An eradication program may be implemented, or a “stop or slow the spread” of Japanese beetle program will be adopted, depending on available resources.

The program will prohibit nursery stock from being imported into the state without an inspection and certification that plants are free of Japanese beetle larvae. The task force will also explore the use of biological control agents such as Ovavesicula popilliae (Protozoa).

Editor’s note: Fairbourn is a freelance writer based in Aurora, Colo. He can be reached at 208-680-3148 or by e-mail at deseretfire@hotmail.com.

Sidebar:

As for protectant products, which are very important for eradication of Japanese Beetle, there are many to choose from, and Gourd advises applicators to be sure and check state and federal labels for usage and application rates. For the control of larvae and grubs, there are:

Sevin (carbaryl), Mach2 (Halofenozide), Advanced Lawn Grub Control, Merit (Imidacloprid) and GrubX (Imidacloprid), Acelepryn (Anthranilic Diamides), Arena (Chothianidin) and Dylox (Trichlorfon).

Control options for adult Japanese Beetle are:

Bayer Advanced Multi-Insect Killer Concentrate (cyfluthrin), Ortho Bug-B-Gon Max (enfenvalarate), Talstar (bifenthrin), Tempo (cyfluthrin), DeltaGard (deltamethrin), Astro (permethrin), Scimitar (Lambda-cyhalothrin); Acelepryn (Anthranilic Diamides) (pending label); Sevin (carbaryl) and Gordon’s Malathion 50 (malathion).