March 2005

6.20

     Beetle larvae feed in groups destroying the upper leaf surface.  Adults chew holes through leaves.
    When populations of this beetle are high, feeding damage turn patches of alder brown leading land owners/ managers to believe that the alder is dead or has been sprayed with an herbicide.  

Defoliation can be complete, but seldom lasts more than one season.  Defoliation does not cause economic loss. Lasting damage from alder flea beetle defoliation is rare. 

     Adults aggregate to hibernate during the winter in debris beneath the tree and in other sheltered places.  Adults are about 1/5 inch long, metallic greenish blue or cobalt blue in color.  Adults will emerge in early spring to resume feeding. 
     Adults mate and lay clusters of yellow/ orange eggs on leaves shortly after emerging in the spring.
     Larvae emerge from the eggs within a few days.  They are 1/5 to ¼ of an inch in length when fully grown, brown/black dorsally and yellowish ventrally with shiny black heads and short legs. 
Larvae reach maturity in August, and pupate on the ground in the duff.  New adults appear in a week to 10

days and feed voraciously on the foliage until the close of the season when they enter hibernation. 
During the late summer/ early fall look for groups of metallic greenish blue or cobalt blue adults chewing holes through leaves.

Alder leaf showing damage from alder flea beetle larvae.  Photo by: Ken Gibson