Bark Beetle Damage
Bark Beetle Description
Although New Mexico bark beetle adults are small, rarely exceeding 1/3 inch in length, they are very capable of killing even the largest host trees with a mass assault, girdling them or inoculating them with certain lethal pathogens. Some species routinely attack the trunks and major limbs of their host trees, other bark beetle species mine the twigs of their hosts, pruning and weakening trees and facilitating the attack of other tree pests. While many devastating species of bark beetles are associated with New Mexico conifers, other species favor broad leaf trees and can be equally damaging.
Adult bark beetles are strong fliers and are highly receptive to scents produced by damaged or stressed host trees as well as communication pheromones produced by other members of their species. The first beetles to attack a potential host tree may be repelled or killed by resins in the bark if that portion of the tree is still relatively healthy. If the tree is too weak to “pitch out” the beetles, infestation proceeds and even more bark mining beetles are attracted to infest the host. In extreme cases where bark beetle populations are exceedingly high, the defenses of even healthy, live host trees can be overwhelmed.
In polygamous species such as the pinon bark beetle, Ips confusus, the male bores a short nuptial chamber into the host’s bark, releases pheromones attractive to his species and mates with 2-3 females. Each female bores her own egg gallery through the live bark at angles to the nuptial chamber. Many, if not all, bark beetle species transport spores of tree fungi that further weaken the host, clogging its vascular system and sometimes killing it before the bark beetles do. Tree fungi transported by conifer-infesting bark beetles in New Mexico are called either “blue stain” or “brown stain” fungi for the colors that streak the wood after it is affected. Some bark beetle species have only one generation annually, especially at higher elevations. Others may complete two to four generations per year. Reproductive activity usually is minimal in the winter.
Recent transplants and trees stressed for whatever reason can be protected from bark beetles with topical applications of labeled insecticides. These treatments should be applied at least to the trunk and major limbs of each tree according to label specifications and prior to the first flights of bark beetles in late spring to early summer. Mallory Landscape and Design, as a licensed Pesticide Applicator, recommends the application of Carbaryl at a 2% rate by volume for bark beetle control.
New Mexico Pesticide Applicator License #55493