Many Japanese imports - from cars and trucks to electronics and video games - have helped to make our lives easier and more enjoyable. But there's one import that gardeners and landscapers wish had stayed at home: The Japanese Beetle.
This pesky little critter is a comparatively recent arrival in the USA, having first been identified in a nursery in New Jersey about 80 years ago.
Now, 80 years might not sound like "comparatively recent" to you until you compare that to the life-cycle of some of the trees you can probably see from your home or office window.
Strangely enough, the Japanese Beetle is less of a problem in its homeland than it is over here. Why? Because in Japan, Popillia japonica Newman (to give the pest its correct entomological name) has natural enemies that keep it in check. But here in the States, without those natural predators, the Japanese Beetle is free to multiply. What's more, it found a pleasant climate and plenty of food... as gardeners and landscapers were soon to discover!
According to the USDA, the Japanese beetle is the most widespread turf-grass pest in the United States. The USDA estimates that efforts to control the larval and adult stages cost more than $460 million a year. Losses attributable to the larval stage alone have been estimated at $234 million per year-- $78 million for control costs and an additional $156 million for replacement of damaged turf.
Unfortunately, these voracious little guys view a whole lot of green stuff as their all-you-can-eat buffet and will chomp their way through more than 300 different plant varieties, eating the tissue between the veins, leaving nothing more than leaf skeletons. The larvae carry out their damage unseen and underground, feeding on plant roots (such as turf grass) resulting in whole patches of dead turf that resemble coconut matting.
How can you recognize a Japanese Beetle or its larvae? According to a web site operated by Ohio State University's Extension Service, the adults are a brilliant metallic green, generally oval in outline, 3/8 inch long and 1/4 inch wide. The wing covers are a coppery color and the abdomen has a row of five tufts of white hairs on each side that are diagnostic.
The larvae are typical white grubs that are C-shaped when disturbed. First instar larvae are about 1/16 inch long while the mature third instars are about 1-1/4 inch long.
So how can the home landscaper deal with these pests?
If you notice just a few Japanese Beetles on your plants, they are probable "scouts" searching for a suitable food source. Carefully inspect your plants and pick off each beetle by hand and drop them into a container of soapy water.
If the beetles are present in greater numbers, you should consider chemical spraying. There are several suitable sprays you can use and you can find a full list at the Ohio State University web site whose address you'll find below. You can also contact me via e-mail if you need some more personal advice.
One way to keep Japanese Beetles away from your landscape is to plant the kind of stuff they DON'T like to eat. Although they'll happily feast on 300+ varieties, they don't care for arborvitae, ash, begonia, bleeding heart,boxwood, columbine, cornflower, daisies, flowering dogwood, firs, forget-me-not, forsythia, hollies, hydrangeas, junipers, magnolias, maple (red or silver only), oaks (red and white only), pines or yews (taxus), to name a few.
The USDA site I mentioned has a comprehensive list of "best" and "worst" plants when it comes to repelling Japanese Beetles from your landscape.
You can find the USDA information here: http://www.pueblo.gsa.gov/cic_text/housing/japanese-beetle/jbeetle.html and the Ohio State web site is http://ohioline.osu.edu/hyg-fact/2000/2001.html