A Field Guide for Ground Checking Southern Pine Beetle Spots
Southern Pine Beetle Handbook
United States Department of Agriculture Combined Forest Pest Research and Development Program - Agriculture Handbook No. 558 - Issued November 1979
Stages of Beetle Attack During The Summer
Stage 1 – Pines with Fresh Attacks
SPB attack sequences and development time are more predictable from May to October, and the appearance of beetle – killed pines change with a distinct pattern. On the basis of these facts, three categories for beetle-infested pines have been established, reflecting various stages of attack. The number of trees in each stage of attack – and where the trees are located in a spot – is likely to spread in warm weather. It is essential, then, that you learn to recognize these three stages to correctly determine the need for control.
When SPB bore into a tree, they produce chemicals attracting other beetles to the trees. This sets off a chain reaction. The attractants usually bring together more than enough beetles to kill the pine, and excess beetles spread to nearby trees. They, too, give off the attractant, it is important to identify their number and location. Only then can you determine if the spot is likely to spread. The following characteristics identify trees with fresh attacks:
|Figure 6. Fresh pitch tube and
SPB adult on stage 1 tree.
|Figure 7. Boring dust in spider
webs at base of stage 1 tree.
|Figure 8. Adult checkered
beetles on stage 1 tree.
|Figure 9. Discolored wood
of stage 1 tree SPB adult gallery.
|Figure 10. Shaved bark with SPB larvae
and pupae in outer bark of stage 2 trees.
|Figure 11. Ambrosia beetle
dust at base of stage 2 tree.
Stage 2- Pines with developing SPB Broods
Soon after adult beetles have overcome a tree, they stop producing attractant. Eggs hatch, and small, white SPB larvae start feeding in inner bark mines, which are mixed among the S-shaped adult galleries (fig. 2). As larvae develop, they move into the outer bark, where they eventually change into white pupae and then into brown or black adults. It is important to realize that the beetle has these various forms. To see the later beetle stages, carefully shave away outer layer of bark with an axe or machete (fig. 10). Other features of trees with developing brood are:
|Figure 12. Brown wood associated
with bark beetle mining in stage 2 tree.
|Figure 13. Checkered beetle
larvae in inner bark stage 2 tree.
|Figure 14. Ambrosia beetle
dust at base of stage 3 tree.
|Figure 15. SPB pitch tubes and
exit holes through bark of stage 3 tree.
Stage 3 – Pines Killed and Vacated by SPB
After maturing in the bark, new adult beetles bore their way out and fly off to attack another pine. A tree is termed "inactive" when no SPB of any stage can be found in it. Other features of inactive trees include:
Figure 16. Wood discoloration caused
by insect and fungal activity in stage 3 tree.
Developed by the University of Georgia Bugwood Network in cooperation with USDA Forest Service - Forest Health Protection, USDA APHIS PPQ, Georgia Forestry Commission, Texas Forest Service
and the Pests and Diseases Image Library - Australia
Last updated August 2018
www.barkbeetles.org version 2.0