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Japanese Beetle
Overview
Japanese Beetles feeding on leaf
Japanese Beetles feeding on leaf.

Fast becoming more of a nuisance around St. Paul, the Japanese beetle is a destructive, exotic pest harming turf, shrubs and trees. Thought to be established only in isolated areas within Saint Paul, there recently have been more wide-spread instances of infestations. The City of Saint Paul does not actively manage Japanese beetles. 

About 1.5 cm long and 1 cm wide, the Japanese beetle has a metallic green head and a copper-colored sheath that protects the wings. Although they are lazy, slow fliers, adults are capable of flying long distances where one study recorded 700 meters in five ours.
See full report at: http://www.agry.purdue.edu/turf/report/2002/page155.pdf 

In a large infestation, adult Japanese beetles skeletonize foliage (see picture at right), leaving only the veins of leaves intact. One alarming fact about their feeding is that they are known to feed on over 300 host plants. Some common examples of trees are linden, birch, and crabapple. Fortunately, most trees are able to recover from this damage and will typically produce new growth once the adult beetles finish feeding. However, plants that are stressed from other factors may not be that lucky. 

Currently, there exists no “silver bullet” to control Japanese beetles. Experience from other states has shown that once Japanese beetles establish in an area they will remain though population size can often fluctuate from year to year resulting in many beetles one year and very few the next. Before starting any control program it is important to conduct a survey to measure the magnitude of the infestation. Several insecticides are available but depend on the timing of application, number of beetles in the area, and whether treatment is in grub or adult stage. Along with chemical controls there are less invasive biological controls, such as certain nematodes and parasites. It is also effective to select landscape and garden plants that Japanese beetles do not feed on to minimize an infestation and the resulting damage. Through various well-timed management techniques, Japanese beetle damage can be minimized, but not eradicated in most cases.



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