Hosts:  Alder

Figure 53. Adult alder flea beetle.

Symptoms/Signs:  Larvae are skeletonizers, meaning that they feed on the tissue between the veins, but leave the veins intact. Adults chew holes in the leaves. Adult beetles are dark shiny blue, and about 5 mm long. The mature larvae are a little longer and narrower than the adults, brown to black above and yellowish below.

Biology:  One generation is reported per year. Adults hibernate during the winter in duff at the base of trees and in other sheltered places. They emerge in early spring to resume feeding. Eggs are laid in clusters on foliage. Larvae hatch and begin feeding within a few days. One source reports that larvae mature in August; but in the Southwest they mature earlier in the season.

Effects:  No long-term effects are documented. Outbreaks are generally short lived and sporadic with heavy defoliation. Trees tend to recover quickly.

Similar Insects and Diseases:  Although other defoliators feed on alder, outbreaks of these other insects have not been reported.

References:  24, 46

Figure 54. Early instar larvae of alder flea beetle on underneath side of alder leaf.

Figure 55. Late instar larvae of alder flea beetle on defoliated alder leaves.

Figure 56. Defoliation of alder caused by alder flea beetle in Arizona.