Three types of pine bark beetles commonly referred to as Ips bark beetles are frequent pests of stressed pines in various locations throughout the United States. These bark beetles feed just underneath the bark of infested trees, girdling them and leading to their death. In addition to feeding in the phloem, bark beetles can introduce blue stain fungi which will colonize the sapwood and cause further dieback. Although Ips beetles primarily focus on dead and dying trees, when populations reach sufficient levels they will infest neighboring healthy trees. Ips attacks are very commonly associated with drought stressed trees.
Management revolves around keeping pine trees healthy as Ips species typically attack stressed trees. Preventive trunk applications of Tengard or Bifen XTS can be applied at 30-60 day intervals. Systemic tree injection applications of emamectin benzoate can be applied for situations were sprays are not feasible.
Cambistat improves the health of trees which improves their ability to withstand stress induced attacks by insects and diseases. For best results, Cambistat should be applied as part of an overall management strategy with cultural practices aimed at improving tree health.
Removal of dead and dying pines is important to reduce beetle populations.
Applications should begin in the spring once temperatures reach 60 degrees or when neighboring trees are showing symptoms. In some cases, follow up treatments will be necessary every 30-60 days until temperatures cool below 60 degrees
Other Treatment Practices
- Cambistat improves the health of trees which improves their ability to withstand stress induced attacks by insects and diseases. For best results, Cambistat should be applied as part of an overall management strategy with cultural practices aimed at improving tree health.
- Adequate water is a key factor in maintaining healthy trees. A slow, deep watering event once every few weeks during dry conditions will help maintain soil moisture levels and minimize the stress that invites Ips beetles.
- Mulch is very beneficial for all trees because it reduces competition with turf and moderates soil temperature and moisture levels. The addition of 3 inches of wood chips or shredded bark under the drip line can have a very beneficial effect by holding in moisture and promoting healthy fibrous roots.
- Immediately destroy pines infested with Ips bark beetle or trees damaged by wind, lightning, fire, disease, insects, or other destructive agents. Leaving injured and weak pines creates breeding material for Ips bark beetle.
Preventative spray treatments work best. Injection of emamectin benzoate works well to kill the beetles but does not prevent inoculation of blue stain fungus.
Signs of Damage
- The first visible symptoms are typically needles turning yellow or red
- Dry reddish brown boring dust is visible in bark crevices
- Pitch tubes usually dime sized or smaller and white to reddish brown are often found in bark crevices
Photo: Timothy Haley
USDA Forest Service, Bugwood.org
Photo: USDA Forest Service Archive
USDA Forest Service, Bugwood.org
Trees At Risk
All three Ips species can infest any pine species within their range, and occasionally other conifers such as spruce, hemlock, and fir.
- Most attacks are initiated by male bark beetles, tunneling through the outer bark and excavating a small chamber in which to mate.
- Mating occurs and females then construct egg galleries, laying eggs in niches chewed on either side of the gallery.
- Eggs hatch and begin feeding outward from the gallery, each larvae creating its own tunnel.
- Larvae pupate at the end of their tunnel, emerging as adults who continue feeding, creating winding tunnels in the inner bark before maturing and exiting through the bark.
- One generation generally is completed in 21-40 days depending on weather.
- Development is much quicker during the hot summer months, but ceases below about 59 degrees.
Always refer to product label for rates and approved uses. Some images courtesy of forestryimages.org or Wikimedia Commons. Use of the images does not imply endorsement of treatments.