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Japanese beetles, Popillia japonica, begin as fairly typical white grubs that curl into a C-shape when disturbed. After spending 10 months in the soil as grubs, adult beetles emerge in the spring. Approximately 7/16-inch long and 1/4-inch wide, the beetles are a remarkable metallic-green color with copper-colored wings.

Pest of the Month: Japanese Beetle

 By Jodi Zirbel


 


What does it look like?


Japanese beetles, Popillia japonica, begin as fairly typical white grubs that curl into a C-shape when disturbed. After spending 10 months in the soil as grubs, adult beetles emerge in the spring. Approximately 7/16-inch long and 1/4-inch wide, the beetles are a remarkable metallic-green color with copper-colored wings. In addition, tufts of white hairs are on either side of the beetles’ abdomen.


 


Host material and range


First detected in New Jersey in 1916, Japanese beetles found a favorable climate with an abundance of food and very few natural enemies. Native to Japan, the beetle has steadily spread to encompass most of the United States east of the Mississippi River and even north of the U.S. border into parts of Ontario.


In the larval stage, Japanese beetles live several inches under the soil, feeding on turf grass roots and other plant material found in the soil. As adults, Japanese beetles feed on more than 300 species of plants eating leaves, flowers and overripe fruit.


 


Current threat


After nearly 100 years of living in the United States, the Japanese beetle remains the most widespread turf grass pest. It is estimated that efforts to control the ravenous beetle reach $460 million annually.


Although there are a host of options for which the Japanese beetle can feed, the pest relies on a technique called “skeletonizing” when feeding on plant and tree leaves. By eating only the tissue between the veins of the leaf, the beetle leaves behind a leaf with a lacey or “skeletonized” appearance. Although one solitary beetle may not inflict great damage, the beetles typically feed in large groups, ravaging plants from the top downward. As a result, trees that have succumbed to these beetles often appear scorched, as if damaged by fire.


Even in the larval stage, Japanese beetles inflict considerable damage to home lawns, parks and golf courses where grubs feed on turf grass roots under the soil, resulting in dead patches throughout the turf.


 


Prevention tips


Because adult Japanese beetles are mobile, they can fly several miles to infest new areas, so there’s no way to completely eliminate their threat. However, one way to prevent damage is to closely monitor turf areas to ensure the beetles don’t advance from the larval stage to adult beetles.


Also, the Japanese beetle is partial to several plant varieties, so plant selection is key as homeowners are replacing or adding to their landscape. Among the list of the beetles’ favorites are Norway maple, Japanese maple, roses, grapes and several varieties of flowering crabapples. By avoiding these varieties especially in areas where the beetle is most prevalent the loss can be minimized.


 


Treatment tips


Several options exist for treating areas that have been affected by adult Japanese beetles.


One of the easiest is to handpick beetles when they first enter a new area. Least active in the morning, the beetles can be shaken off a plant and into a bucket of warm, soapy water. In addition, the presence of beetles on a tree or other planting is thought to attract additional beetles, so this will help to prevent rapid infestation.


Another highly effective method to suppress adult feeding damage on trees is the use of a trunk micro-infusion application insecticide, including those that contain imidacloprid. These will start to control infestation as quickly as one to seven days upon application, and will often provide protection through the life of the adult beetle.


One method that gained attention is Japanese beetle traps. However, research from the University of Kentucky showed that the traps attract more beetles than are actually caught.


 


What can you do?


Monitor trees and other plants — especially those most prone to Japanese beetle attacks — for early diagnosis. In addition, watch turf grass areas for large dead patches or the exposure of white grubs when the sod is rolled back.


 


Jodi Zirbel is with Epic Creative, Wis. Article provided by Mauget, a leader in micro-injection and micro-infusion tree care. Contact Mauget or visit www.Mauget.com to learn more about Japanese beetles, prevention tips and proper pesticide application and use.

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