Pests and Pest Control

Waging War on the Japanese Beetle

by Ted Mills

It was in 1916 that an Asian ship, laden with Japanese beetle-infested iris roots and shrubs, made its entry into a New Jersey port. The accidental introduction of these foreign insects has caused unfortunate gardeners and landscapers to suffer the beetle scourge ever since. Since this insect travels limited distances from incubation point, the journey westward has been rather slow. Most gardens west of the Mississippi River have not experienced beetle damage as yet. But beware, these pests are beginning to cry out, "Westward ho!"

Many rosarians are known to throw up their hands in complete surrender to the Japanese beetle. And really there is no easy solution to the problem. It's .a matter of superior numbers of beetles that makes the job of elimination so difficult. However, a few combative actions on the part of the rosarian will limit the degree of damage wrought by this cursed insect.

First, the rosarian must remove all beetles that are found on the plants each day during the infestation period. A good method is to shake them into detergent water. Angered by the destruction caused by the beetle prompts many rosarians to mash them with a temper tantrum of vengeance. However, if this method is used, do not leave the dead beetles lying on the ground. Eggs from the dead female beetle will hatch and reign havoc on next year's rosebushes. Also the juices from the dead beetle will attract other beetles to the spot. Beetle traps are not recommended as a method to eliminate these beetles since traps seem to attract more beetles to the rose. If traps are used, place them a substantial distance away from the roses.

Proper disposal of the dead beetles is important. It would be ideal to burn them to a crisp, but this method may not be practical because of burning ordinances. However, to ship them away in the garbage means that hordes of these worrisome pests will incubate in area landfills and annoy gardeners living nearby. Remember – for every thousand female beetles flying around, there are 50,000 grubs in the ground waiting to reach adulthood and ravage surrounding vegetation, particularly roses.

After the daily removal of beetles is accomplished, the crafty rosarian will spray the blooms and tender foliage at the top of the bush with liquid Sevin. The beetle's preference is a fragrant bloom of light color; however, tender foliage is appetizing when blooms are not available.

Spraying with liquid Sevin every two days is very effective. This frequency is necessary since the chemical's potency is only 48 hours in most cases. This spraying must be continued regularly during the beetle's adult life cycle which is about two and a half months - early to mid summer. Mixing Sevin with other insecticides is not recommended.

The female Japanese beetle lays one to four eggs daily during her brief adult life. She will fly to the nearest grassy area (preferably moist) and burrow 1 to 4 inches into the ground to deposit her eggs. Usually this production will amount to 4 to 60 eggs per season from each female. The eggs will hatch and the resultant grubs will burrow further into the soil and feed on available grass roots. Remaining in the grub stage for about 10 months (until around late spring) the beetles then enter the pre-pupa and pupa stage for a brief time. Upon reaching adulthood, these pests immediately begin to copulate and start devouring vegetation (especially roses) until leaves appear as lace, and blooms are spoiled beyond description.

The most effective method of Japanese beetle eradication is to treat the surrounding area with a product called Milky Spore. However, it is imperative that all the grassy spots in the immediate area be treated. This usually requires neighborhood participation to completely eliminate the beetle population. Unfortunately, the expense of the operation discourages nongardening neighbors' participation.

Milky Spore very effectively produces a fatal disease among the beetle population. Once a level teaspoon of the powder is applied on 4-foot checkerboard centers in the grass, rain or sprinkler systems will cause it to quickly spread as ink on a blotter until the entire area is treated. Do not mix the powder with water to use as a spray since this dilutes it too severely. Once the dry powder is applied, do not cut the grass until is has had a chance to be watered in.

According to published claims of the Milky Spore producer, the effectiveness of this powder is triggered as beetle grubs touching it are infected by a fatal disease originating from the spores. The disease spreads as beetle grubs touch one another. Claims of the manufacturer state the beetle grub actually becomes a factory that produces billions of deadly spores that completely cover the larvae-infested area. Fear not that useful earthworms or friendly insects will be destroyed. Milky Spore affects only Japanese beetle larvae. Once an area is completely covered with the spores, its effectiveness is thorough and the beetle problem is eliminated simply because these pests will not reach adulthood. The chain of beetle reproduction is terminated. The crowning feature of Milky Spore is that subsequent application of the product is unnecessary. The treated area will continue to act as a "mine field" for beetle grubs year after year.

Remember – as mentioned in the beginning – diligence is the key to a successful campaign against the Japanese beetle. It is a daily chore. Don't despair. Work at it and your rosebushes will reward you with unblemished blooms and unspoiled foliage rather than provide a meal for hungry beetles.