Many people in Boulder will attest to the destructive nature of the Walnut Twig Beetle. Adult beetles travel from April to September, and are so small they often go unnoticed. Damage can be extensive when the population of the beetle reaches into the hundreds and thousands. Adding insult to injury, the adult beetle also carries a virulent disease known as Thousand Canker Disease. This pathogen causes large vascular cankers to form underneath the bark. Movement of water and nutrient resources comes to a standstill and large limbs begin to dieback quickly. Over 700 Walnut trees have been removed in the Boulder area due to this beetle and pathogen combination in the past few years. We tracked the movement of this pest into northwest Arvada last year, and into Cherry Hills and Englewood this year. Walnuts throughout Denver were attacked last year, and are now quickly declining.

Current programs are available to help prevent an attack. Programs include multiple trunk applications, as well as soil injections of insecticides. If we stay vigilant with removing attacked and diseased trees there is a hope to save some trees. Some small communities are even organizing a tree inventory to identify where the Walnut trees are and to spread awareness of the problem. If you or your community would like information or help in developing a program, please let us know.