Bark Beetles
FIELD GUIDE TO INSECTS AND DISEASES OF ARIZONA AND NEW MEXICO FORESTS
Southern Pine Beetle and Mexican Pine Beetle
Dendroctonus frontalis (Zimmerman)
and Dendroctonus mexicanus (Hopkins)

Hosts:  Chihuahua, Apache, ponderosa pines

Figure 112. Figure 112. Egg and larval galleries of southern pine beetle. Note that egg galleries are S-shaped that crisscross one another in the inner bark and on the wood surface.

Symptoms/Signs:  Presence of reddish brown boring dust caught in bark flakes and crevices around tree; numerous pitch tubes on the bark at the entry point of the tunnels. In heavily attacked decadent trees, pitch tubes are often missing or so small they can only be seen up close. Later, the foliage begins to fade, turning from green to yellow or bright red, and eventually a dull brown. Woodpecker activity on the trunk is also a good indication that bark beetles have attacked the tree.

Adults are dark reddish brown, cylindrically shaped beetles approximately 3 mm in length. Larvae are white, legless grubs. The morphology of southern pine beetle and Mexican pine beetle are very similar and, therefore, are difficult to tell apart. Taxonomists use the seminal rod of male beetles as the distinguishing characteristic.

Biology: Although southern pine beetle has many generations in the southeastern U.S., it likely has only one to two generations per year in the Southwest depending on elevation and climate. Adults construct winding galleries in the inner bark, where eggs are deposited in individual niches on each side of the galleries. The larvae mine for a short distance before boring into the outer bark where they pupate. Mexican pine beetle is thought to have a similar biology.

Figure 113. Figure 113. Chihuahua pine mortality caused by southern pine beetle in Chiricahua Mountains, Arizona.

Effects:  Southern pine beetle and Mexican pine beetle killed large numbers of Apache and Chihuahua pines throughout 1999-2001 in the Chiricahua Mountains of southeastern Arizona. Pine mortality ranged from single trees to large groups of more than 100. Southern pine beetle has been collected from traps in northern Arizona.

Similar Insects and Diseases: Southern pine beetle and Mexican pine beetle can be distinguished from other pine bark beetles by the shape of egg galleries and beetle morphology. Western pine beetle egg galerries are similar in appearance; however, larval feeding galleries on the inner bark are absent.

Reference:  104