Well, it looks like it’s time for another favorite of mine, the Japanese Beetle, to appear! These guys love to decimate my roses! Both as adults and as grubs (the larval stage), Japanese beetles are destructive plant pests. Adults feed on the foliage and fruits of several hundred species of fruit trees, ornamental trees, shrubs, vines and vegetable crops. Adults leave behind skeletonized leaves and large, irregular holes in leaves. The grubs develop in the soil, feeding on the roots of various plants and grasses leaving those attractive brown spots in your lawn.
No quick fixes can rid homeowners of the Japanese beetle once it becomes established. However, scientists with the U.S. Department of Agriculture’s (USDA) Agricultural Research Service (ARS) and Animal and Plant Health Inspection Service (APHIS) have developed an integrated pest management (IPM) program for homeowners based on field experiences. Following is some information from the USDA website (http://www.aphis.usda.gov/lpa/pubs/pub_phjbeetle04.pdf):
Traps for adult beetles operate primarily with two chemical lures. A combination of a pheromone, or sex attractant, and a floral lure attract both male and female adult beetles to the trap. Then, as a result of their clumsy flying and the design of the trap, they end up caught in either the bag or funnel portion of the trap.
Japanese beetle traps can be used to assess the beetle population in a given area. For instance, if you put a trap out while the adults are flying and find that beetles fill the trap in 1 day, you probably have a Japanese beetle problem. If, during a week, the bottom of the trap is barely filled, you probably do not need to be concerned. Adult beetles can fly long distances, so those caught in your yard may have come from several hundred yards away. For this reason, it is difficult to estimate the number of grubs in your turf from adult trap catches. To survey for grubs, you need to calculate the number of Japanese beetle grubs per square foot in your lawn.
This estimate is important for deciding the severity of your white-grub problem and whether treatment is necessary.
Japanese beetle grubs can be sampled in late summer (August to October) and late spring (April to June). Timing will vary by geographic location.
If your lawn has brown or dead areas, during the normal growing season, survey near the edge of the damage. If you find that grubs are the cause of the damage, clearly this area should be treated. Otherwise, take several randomly selected samples throughout the lawn. The density of Japanese beetle grubs
often varies widely within a small area, so by taking several samples, you may be able to pinpoint the damage and therefore selectively treat specific areas
rather than the whole lawn. Using a shovel, dig a square hole 8 by 8 by 3 inches
deep in the turf. Turn the sod over on some newspaper and search the grass roots and the soil in the hole for grubs. Turn the turf back into the hole and add water to
help the grass recover. Record the number of grubs found in the sample location so you can map out or average grub densities. To convert these numbers to the number of grubs per square foot, multiply them by 2.25. Generally, you should consider treating areas in your lawn with more than 10 grubs/ ft2.
Homeowners who choose biological methods to control Japanese beetle populations can successfully use parasites, nematodes, fungi, or other biologically based approaches. Some of these agents are commercially available to homeowners; others are not. While they take a little longer to produce the same results as insecticides, biological control agents last longer in the environment. More importantly, they do not adversely affect non target or potentially beneficial organisms.
Nematodes—Insect-eating nematodes—microscopic parasitic roundworms—actively seek out grubs in the soil. These nematodes have a mutualistic symbiotic relationship with a single species of bacteria. Upon penetrating a grub, the nematode inoculates the grub with the bacteria. The bacteria reproduce quickly, feeding on the grub tissue. The nematode then feeds on this bacteria and progresses through its own life cycle, reproducing and ultimately killing the grub. The two nematodes that are most effective against Japanese beetle grubs are Steinernema glaseri and Heterorhabditis bacteriophora. The latter is commercially available. When using nematodes, remember they are alive and have a fairly high oxygen requirement. They are typically sold on a carrier, which they can survive on for a month or 2 under cool conditions. They can be applied with any standard insecticide applicator. Once mixed with water, nematodes must be applied fairly quickly. Follow accompanying directions carefully for best results. Nematodes may be purchased in lawn and garden shops or through biological mail-order catalogs.
Bacillus thuringiensis (Bt)—Bt is a naturally occurring soil bacterium typically used as a microbial insecticide. The Bt strain registered for the Japanese beetle is for use on the grub stage only. Bt is a stomach poison and must be ingested to be effective. Apply it to the soil as you would insecticides. Effectiveness is similar to that of insecticides. Check with your extension agent regarding the availability of Bt.
Milky Spore—Milky spore is the common name for spores of the bacterium Bacillus popillae. This bacterium was first registered for use on turf in suppression
of the Japanese beetle grub in the United States in 1948. Upon ingestion, these spores germinate in the grub’s gut, infect the gut cells, and enter the blood, where
they multiply. The buildup of the spores in the blood causes the grub to take on a characteristic milky appearance. Milky spore disease builds up in turf slowly (over 2 to 4 years) as grubs ingest the spores, become infected, and die, each releasing 1–2 billion spores back into the soil. Milky spore disease can suppress the development
of large beetle populations. But it works best when applied in community wide treatment programs. Check with your extension agent regarding the availability of milky spore material.
Parasites—Releasing natural enemies or parasites of an exotic insect is a successfully proven method to reduce pest populations. Introduced parasites must be shown to be host specific (that is, to parasitize only the target pest) before USDA approves releasing them. Two such parasites of the Japanese beetle have been brought to the United States from Asia. Researchers have successfully established these insects in areas inhabited by the Japanese beetle, and the parasites are now functioning as important biological control agents of the beetle. Tiphia vernalis, a parasite of the Japanese beetle grub, and Istocheta aldrichi, a parasite of the adult, have been shown to be important in regulating the population dynamics of the beetle in many areas of the Northeastern United States. These parasites are not yet commercially available; however, you can contact your local extension agent
to see if they are established in your area. If they are, planting the appropriate food plants will attract these parasites and increase the rates of parasitization, and thus help control the Japanese beetle on your property. Tiphia vernalis—This small, parasitic wasp of Japanese beetle grubs resembles a large, black, winged ant. Its current distribution is believed to be throughout the Northeastern United States and south to North Carolina. After a brief period of feeding and mating during the spring, the female wasp digs into the soil, paralyzes a beetle grub by stinging, and then deposits an egg on the grub. When the egg hatches, the emerging wasp larva consumes the grub. Food sources: Adult wasps of this species feed almost exclusively on the honeydew of aphids associated with the leaves of maple, cherry, and elm trees and peonies. The nectar of tulip poplars has been found to be an important food source for the adult wasps. Istocheta aldrichi—This solitary fly is an internal parasite of the adult Japanese beetle. The female flies are capable of depositing up to 100 eggs during a period of about 2 weeks. The eggs are usually laid on the thorax of the female beetles. Upon hatching, the maggot bores directly into the beetle’s body cavity, killing the beetle. Because it does not take this fly long to kill the beetle, I. aldrichi can suppress Japanese beetle populations before beetles can reproduce.
Millions of beetles are captured annually in mechanical traps. This method is an easy and inexpensive way to reduce beetle populations and curtail egg laying. Under favorable conditions, a trap will capture only about 75 percent of the beetles that approach it. Because the traps actually attract more beetles than they capture, be sure not to put traps near your garden or your favorite plants. Put traps at the borders of your property, away from plants the beetles may damage. Traps are most effective when many of them are spread over an entire community. Homeowners who choose to give the mechanical traps and lures a try as part of their IPM program can typically find them at yard and garden centers. Traps should not stay in place year ’round because the lures inside get stale. Trap placement should be timed to coincide with the emergence of adult Japanese beetles in your area. Adults generally emerge between early June and late August. Check with your extension agent for information of the Japanese beetle flight period in your area. If Desperate: The following chemicals are effective for use in the control of the Japanese beetle adult and its grubs:
If Desperate: The following chemicals are effective for
use in the control of the Japanese beetle adult and its
Regulated Chemicals for Adults:
Regulated Chemicals for Larvae:
Imidacloprid (Merit® Insecticide for
turf; Marathon® for nursery use)