Bark Beetle Pest Alert

Southern Pine Engraver
Ips grandicollis (Eichhoff)

Introduction/Symptoms: The lack of precipitation the past couple of years made conditions favorable for an increase in bark beetle populations in red pine plantations in southern Wisconsin. If dry conditions persist additional damage is likely to be observed. The map on the right shows locations in Wisconsin where southern pine engraver was observed causing mortality.

The southern pine engraver, Ips grandicollis, is often associated with attacks caused by the more common pine engraver, Ips pini. In stands recently observed, the southern pine engraver is initiating attacks in the upper most portions of red pine crowns, killing individual branches and eventually the entire tree, in the absence of, or prior to, attack by I. pini. Pictured on the left is the initial attack by southern pine engraver showing mortality of individual branches in the upper crown of red pine.

Close inspection of dead branches, reveal the nuptial chamber and gallery mining caused by the southern pine engraver. Shown above is the Southern pine engraver nuptial chamber with gallery tunneling in small branches.

As the branches in upper crown die, the bark beetles then move into the main trunk as shown in the picture on the right and eventually girdle and kill the entire tree. As the population builds adjacent trees are attacked and eventually a "pocket" of dead trees is created.

Biology: The adult southern pine engraver shown on the left over winters in the duff layer. Note the five projections on back wing cover. In the spring it emerges and seeks out fresh slash, logs, or stressed trees to breed in. The males initiate a reproductive attack and create a nuptial chamber to mate with multiple females. The females create egg niches to lay their eggs. The eggs hatch and small cream colored larvae chew galleries just under the bark layer in the phloem tissue which eventually girdles and kills the tree as shown in the picture above and to the right. The beetles may go through 2-3 generations per season. Windstorms or summer tree harvesting operations can allow for excessive breeding material and rapid population build up. Dead trees, with loose bark, are no longer suitable breeding material and pose no risk in beetle population buildup.

Management Recommendations:

1. Maintain stand vigor by avoiding over-stocking and by avoiding over-mature stands.
2. If low vigor due to drought or defoliation, consider pre-salvage harvest.
3. Storm-damaged material should be harvested or monitored for build up of the bark beetle population.
4. Thinning is best done between September and March.
5. If summer thinning is necessary:
• Tops should be utilized down to 2-inch top.
• Leave branches attached to stem wood to speed drying.
• Remove cut products from stand within 3 weeks of cutting.
• Beetle population in slash should be monitored: if dangerous level occurs, mangle bark by driving over it with a tracked vehicle or chip slash.
6. If a group of trees are attacked, a well-timed harvest of attacked and adjacent low-vigor trees during the growing season may eliminate or help to reduce local populations.

Additional Observations: The fungal shoot blight disease, Sphaeropsis sapenia, has also been observed attacking these trees and is likely an additional factor in the ability of the southern pine beetle to successfully attack the crown branches as shown on the right. Armillaria root rot and turpentine beetle attacks may also be present in these affected stands.

Armillaria mycelial fan under bark of recent dead red pine tree.

Forest Health Protection