Twobanded Japanese Weevil – Another Invasive Pest

The twobanded Japanese weevil, Pseudocneorhinus bifasciatus is an invasive pest that has been in the U.S. for a century and is now found in Iowa.  Individuals were collected in Ames, IA in early August. 
Twobanded Japanese weevil adults have a broad host range and feed on the leaves of many common ornamental plants. Their feeding starts as notches along the margins of leaves and sometimes whole leaves are consumed.

There are over 100 host plants including:

  • barberry
  • privet
  • lilac
  • rose
  • spirea
  • forsythia
  • viburnum
  • euonymus. 

Adult weevils are about one-quarter inch and are mottle brown in coloration. See photos below.   Larva feed blow ground on plant roots.  In Iowa it is most likely there is only one generation per year with adults appearing in late June to early July.
Leaf damage by adults will be primarily cosmetic and management is not necessary for most homeowners.

Japanese weevil on a leaf
The twobanded Japanese weevil feeds from the edges of the leaves on a wide variety of plants.
Japanese weevil eating a leaf
Twobanded Japanese weevils are about one-quarter inch long and mottled brown in color.
Japanese weevil damage on a lilac leaf
Weevil feeding damage to edges of lilac leaves.

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