Ips beetles

Natural History
Adult and larval galleries of Ips avulsus
Photo credit: Ronald F. Billings, Texas Forest Service, Bugwood.org

Ips beetles are a genus of pine bark beetles represented by three species in Florida: Ips avulsus, Ips grandicollis, and Ips calligraphus. These beetles usually attack only a small number of trees at one time but under the right conditions, Ips beetle attacks can become more widespread. Ips beetles prefer to attack weakened trees and thrive in hot weather.

Adult beetles invade a new host tree and soon the females lay eggs. Several days later the eggs hatch and the larvae begin eating the inner bark of the host tree. Adults carry a fungus into the tree and use this fungus serves as part of their food source.

Trees are damaged by the insects as they excavate galleries in the phloem. These galleries cut the phloem cells that transport food throughout the tree. The blue stain fungus grows from the galleries into the wood, blocking the xylem cells that carry water through the tree. Eventually the tree dies. Healthy trees can fight off an attack by producing lots of pitch that acts as a barrier against the beetles.


Identifying Characteristics

Identifying the injury: Needles of infected trees will turn from green to yellow to red to brown. Small, reddish-orange colored masses of resin, called pitch tubes, may be found on tree stems and branches. Pitch tubes are not always present, especially on trees that are severely stressed. The beetles leave small, 1/16" to 1/8", round holes in the outer bark. Reddish-orange to brown boring dust can be found in bark cervices and in the area underneath the tree. If the outer bark is removed, you can see the narrow Y or H shaped galleries.
Identifying the insect: Adult beetles are small, ranging in size from 1/8" to 1/5" long and are dark brown to black in color. Ips beetles can be distinguished from other bark beetles by several, small, spine-like projections found along tback section of the insect. This back section is concave, not rounded like the back parts of other bark beetles.
Susceptible trees: The Ips beetles can attack any southern pine. The beetles prefer trees weakened by drought, lightning, flooding, and other types of stress such as root diseases.



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