Beetlemania

By Chuck Martin, Dow Gardens Horticulturist

Remember the sixties and the British invasion of music into the US?  This invasion caught us off guard. Parents thought it was the end of our civilization and teenage girls were crying and tearing their hair out at the sight of a musical group from the British Isles called the Beatles. The Beatles changed our music forever.

I see the same hysterical reaction that occurred in the sixties, taking place now by gardeners.  People are afraid that gardening will come to an end.  I’ve seen grown men crying over their lawn.  The cause of this entire hysteria is over a beetle from the isle of Japan.  The Japanese beetle is changing gardening forever. 

Let me quote a national garden supply company to add to your gardening fears.  “Japanese beetles are just about the worst pests your garden can have.  As adults, they ravage your flowers and vegetables.  As young grubs, they devour your lawn’s root system and attract skunks and moles.”   After reading this quote, I contemplated getting out of gardening.  I am here to tell you, just like we were able to get through the British invasion of the sixties, we will survive the Japanese beetle invasion of the 90’s.

The first thing we need to know in order to conquer this enemy is their life cycle.  By knowing the Japanese beetle’s life cycle we will know were they are hiding out and attack them at that location. 

The adults will usually emerge during the later part of June and continue throughout July.  The problem with these pesky beetles is that they will be attracted to about 300 different plant types.  Even though they have a preference in which plants they enjoy eating, we have to keep watch over many of our ornamentals.  The first beetles to emerge will seek out a suitable food source and release an aggregation pheromone or a party announcement that attract additional adults.

Adults are about 3/8 of an inch long and have a beautiful metallic green color.  The beetle can be confused with another beetle called False Japanese beetle but the distinguishing  characteristic of the Japanese Beetle is the 5 white dotes created by hair tufts along each side of their abdomen.

The adult females believe in free love similar to those hippies of the 1960’s, and release a sex pheromone to attract males.  After munching and mating for a couple of days the females will burrow in to the soil 2 to 4 inches and lay 1-5 eggs.  After laying the eggs they go back to party for a couple of days until they need to lay more eggs.  This cycle continues until the female lays between 40 and 60 eggs.

The eggs will hatch in 17 to 25 days and begin munching on grass roots.  The larva or grub stage of the Japanese beetle is “C” shaped.  These grubs are a delicacy to skunks and crows and will tear up your yard in order to find the grubs.

In September and October the grubs will dig deep into the soil to over winter and then return to the soil surface in mid-April.  They will continue to eat up the roots of your lawn until Mid-May when they pupate. 

The young July grubs are the easiest to control.  If you had a problem last year with grub damage you might want a systemic insecticide in July to control the grubs.  Systemic insecticide need to be applied in July.  This early application allows the plant to take up the insecticide in time to make their roots poisonous to the grubs.  Imidacloprid (common name) or Merit (trade name) is the insecticide most entomologists are recommending for early grub control. 

If you aren’t sure if you will have grub damage, you can survey your property by removing a square foot of sod 3 inches deep.  Consider treatment if the population is between 10 and 15 grubs.  Irrigated turf will tolerate a higher population.

Plants that are susceptible to the adult’s eating and mating rituals can be sprayed with an insecticide.  The spraying will have to be on a regular basis since the adults keep emerging during the summer months.

Many people try trapping the adult beetles by using a floral lure and sex attractant as enticement.  In most urban areas the traps will only attract more beetles into the area.  It is best to give the traps to a neighbor you dislike for Christmas.  This will encourage a higher population in their yards.

As natural parasites and predators of the Japanese beetle build up in our area, the beetle will level off and be less of a concern.  We saw this with the Gypsy Moth and I believe we will eventually see it occur with the Japanese beetle.

Of all the articles that I have written, this article is the most accurate because Elly Maxwell the entomologist at Dow Gardens, and my wife Beth have both edited it.