Hosts: Ponderosa pine, piñon, and
Trees attacked and colonized by twig beetles exhibit fading
needles on twigs and branches, and twig and branch dieback throughout
the crown. Tan sawdust is produced around the attack sites. On smaller
twigs and branches, most of the cambium is mined beneath the bark.
Small, star-shaped egg galleries generally occur under the bark
of the larger branches and small trunks.
Biology: Adult twig beetles are about 3
mm long and dark brown. Most species have a rounded rear end, but
a few have a pair of short spines. The larvae are fat, white, C-shaped
grubs with light brown head capsules and feed under the bark. Most
species have 2 to 4 generations per year, depending on local conditions.
Effects: Typically attacks and kills small
twigs and branches of drought stressed or otherwise weakened pines
and other conifers. Although twig beetles are generally considered
of secondary importance, under favorable conditions they may develop
in sufficiently high numbers and attack and kill small trees. Pityogenes
carinulatus killed thousands of young ponderosa pine in 1967
in New Mexico as a result of populations increasing in thinning
and logging slash. Twig beetles infested high numbers of young piñon
in 2002, 2003, and 2004 across New Mexico and Arizona.
Similar Insects and Diseases: See Ips
discussion. Most twig beetles have elytral declivity and egg galleries
that are somewhat similar to Ips; however, twig beetles
are smaller in size and are typically found in branches and very
small diameter trees.