Buds and Shoot Insects
FIELD GUIDE TO INSECTS AND DISEASES OF ARIZONA AND NEW MEXICO FORESTS

Juniper Twig Pruner
Styloxus bicolor (Champlain and Knull)

Hosts:  Juniper and Arizona cypress

Figure 167. Figure 167. Damage to junipers caused by the juniper twig pruner.

Symptoms/Signs:  The junipertwig pruner is a small longhorned beetle (Cerambycidae). The adult is 7 to 11mm long and has a reddish-orange head and brownish to black body. Larvae are small, white roundheaded borers.

Figure 168. Figure 168. Closeup of damage to juniper shoots caused by the juniper twig pruner.

Biology:  The life cycle may take as long as 2 years to complete. Eggs are laid on branches, often near an intersection of twigs, 0.5 m from the branch tip. Grubs kill twigs by boring through the centers.

Effects:  Juniper twig pruner causes twig dieback on junipers and cypress growing throughout the Southwest.

Similar Insects and Diseases:  Cedar bark beetles and western cedar borer.

References:  9, 43

Figure 169. Figure 169. Exit hole of juniper twig pruner.