Banded alder borer, or California laurel borer—Rosalia funebris
This longhorned beetle, or roundheaded wood borer (Cerambycidae), feeds during its larval stage in declining or dead branches of broadleaf trees, including alder, ash, California bay, oak, and willow.
Adult banded alder borers have wing covers with several black and pale bands (gray, light bluish, or white) and a pale thorax with one large black spot. The pale larvae occur under bark. The adults and mature larvae are to 1 to 1-1/4 inches long.
Adults are sometimes mistaken for the Asian longhorned beetle, a damaging exotic pest that is not known to be established in California. Examine the thorax (segment directly behind the head) and wing covers to distinguish the similar species. The banded alder borer thorax is white with a single, large, black spot that is one-half or more of the width of the thorax. On the Asian longhorned beetle, the thorax is entirely shiny black. Submit any suspected Asian longhorned beetles to the county agricultural commissioner.
Life cycle
Longhorned beetles develop though four life stages—egg, larva, pupa, and adult. Adult banded alder borers emerge and mate from April through August. Adult females lay eggs individually on small- to medium-sized, dying or recently dead branches. The eggs hatch within 2 weeks and the larvae bore in and feed for 6 to 7 months under the bark. Mature larvae then bore in more deeply to overwinter as pupae. In the spring, pupae develop into adults, each of which chews an exit hole and emerges from the branch.
Damage
Larvae feed and develop in branches of various woody broadleaves. Since banded alder borer larvae only feed in dead branches or those dying from other causes, the feeding by this insect is easily overlooked. This native species generally is not the original cause of dieback and is not a significant pest.
Solutions
Plant trees that are well adapted to the site conditions, provide proper cultural care, and protect trees from injuries. Prune off dead limbs during the season when adult borers are not active. Promptly remove dead or dying trees. Do not store freshly cut wood near trees; debark or solarize logs beneath clear plastic in the sun to prevent beetles from emerging from the wood and attacking nearby hosts.
To avoid spreading wood-boring pests, do not move firewood or logs to other counties. Purchase firewood near where you will burn it, and leave any unused wood on site rather than moving it or bringing it home. |
Banded alder borer adult
Roundheaded wood borer larva
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