Insect to Injury?

 

With plenty of doomsday hysteria circulating about the destruction of western forests from the mountain pine beetle epidemic, the U.S. Forest Service is attempting to allay fears about another beetle on the rise – a 2mm-long twig beetle, Pityogenes plagiatus knechteli, that’s killing younger trees in mountain pine beetle-affected areas throughout Colorado and Wyoming.

First observed in high numbers several years ago, twig beetles, and the tree mortalities they're causing, have generated more inquiries from the public of late. As a result, the U.S. Forest Service Rocky Mountain Region released an interagency memo recently updating officials about the status of the twig beetle, which is boring into the upper boles and branches of mountain pine beetle-infested lodge pole pines as well as un-infested smaller lodge poles, mostly less than seven inches in diameter. Homeowners should avoid transplanting lodge poles, it recommends, and keep trees well-watered, though no further actions such as preventative spraying are currently being taken.

“This is not an unexpected event,” says Bob Cain, entomologist for the U.S. Forest Service, who predicts this twig beetle infestation is unlikely to become an epidemic.

Really, it’s a textbook story in beetle population dynamics: Big beetle invades big forest, eats it down to a small forest; small beetle attacks small forest, eats it down to a smaller forest.

The process of small beetle following big, known as a secondary infestation, has been documented as far back as the 1930’s, when researchers tracked a mountain pine beetle epidemic in Montana’s Beaverhead National Forest between 1927 and 1938. The study, published in 1940 in The Journal of Forestry, noted twig beetles in high numbers only during the tail end of that period, from 1933 to 1936, when they killed 3.4 million trees – a small bite compared to the 20.2 million trees eaten over 11 years by the mountain pine beetles. Of those 3.4 million, nearly 80 percent stood less than seven inches in diameter.

Since most salable trees are greater than nine inches in diameter, the twig beetles pose little economic threat to remaining lodge pole forests in Colorado and Wyoming. Some trees will die, of course, but Cain doesn’t foresee any additional die-off having a significant impact on lodge pole forest ecology.

“Twig beetle-caused tree mortality should decline in the next few years,” he says. “And we do not anticipate that they will cause stocking concerns in stands of younger trees.”

Trees attacked by mountain pine beetles slowly fade to gray after about a year, whereas twig beetle-infested trees often quickly turn red, sometimes within weeks. Aerial surveys – perhaps the most effective method for measuring beetle damage – can hopefully delineate gray from red by as early as the new year.

Cain admits, however, that twig beetle activity tends to be scattered and less noticeable than that of the mountain pine beetle. "There's no way to distinguish the size of the tree that's fading," he says. "So it's impact is going to be difficult to detect from the air.”

Adam Petry is a biologist and HCN intern.

High Country News Classifieds
  • GILA NATIONAL FOREST
    9+ acre inholding. Passive solar strawbale off the grid and next to the Continental Divide Trail in ponderosa pine/doug fir forest at 7400.
  • HIRING BEARS EARS EDUCATION CENTER DIRECTOR
    Conservation nonprofit Friends of Cedar Mesa in Bluff, Utah is hiring an Education Center Director to oversee the operation of the Bears Ears Education Center....
  • PROGRAM MANAGER, SUSTAINING FLOWS
    Friends of the Verde River, Cottonwood, AZ. Apply at https://verderiver.org/employment-opportunities/
  • PROGRAM ASSOCIATE - VERDE RIVER EXCHANGE
    Verde River Exchange - Friends of the Verde River, Cottonwood, AZ. Apply at https://verderiver.org/employment-opportunities/
  • CODE COMPLIANCE OFFICER
    Teton County Planning & Building is hiring! Our ideal candidate is a team-player, a problem-solver, pays attention to detail, and can clearly communicate technical material...
  • ARCHITECTURE DRAFTSPERSON/PROJECT MANAGER
    Studio Architects is seeking a full time Architectural drafts-person/project manager with1-3 years of experience to join our firm. At Studio Architects our mission is to...
  • ASSISTANT MANAGER/TRAINEE, COLORADO RANCH
    needed for 16,000+ acre conservation property in south central Colorado. Qualified candidate would have experience working on a ranch or wilderness property, general forestry/fire management...
  • FARM HAND &/OR NANNY IN ESCALANTE
    Nanny for 18-mnth-old. Yearly salary, vacation, health insurance. Spanish/other foreign-language native spkr prefrrd.
  • EXECUTIVE DIRECTOR
    Washington Association of Land Trusts seeks an ED to build on WALTs significant success & to lead the association to new levels of achievement. See...
  • BEAUTIFUL CUSTOM STRAWBALE HOME IN WESTERN COLORADO!
    Secluded, energy efficient Southwestern home on 40 wooded acres. Broker - Rand Porter - United Country Real Colorado Properties. 970-261-1248, $425K
  • FORMER RETREAT CENTER/CONSERVATION PROPERTY FOR SALE
    57 acres in Skull Valley, AZ, 17 miles from Prescott, year-round creek, swimming holes, secluded canyon, hiking/meditation trails, oaks, pines, garden, greenhouse. House, office building,...
  • ARIZONA PUBLIC LANDS ORGANIZER
    Title: Public Lands Organizer About the Arizona Wildlife Federation (AWF) The AWF is a non-profit organization dedicated to educating, inspiring, and assisting individuals and organizations...
  • HISTORIC RANCH HOME W/ 20 ACRES
    Historic 1893 Ranch Headquarters. 4 Bdrm, 3.5 Ba, 4000 ft2. Remodeled 2002. Includes 2 studio apts, stables, arena, workshop, 5 RV hookups. Chirachua & Peloncillo...
  • VICE PRESIDENT OF RETAIL OPERATIONS
    The Vice President of Retail Operations will provide overall leadership and accountability for purchasing, product development, merchandising planning, visual merchandising, retail operational excellence, oversight and...
  • ASSOCIATE DIRECTOR
    Grand Staircase Escalante Partners seeks an experienced fundraiser with excellent communication and organizational skills.
  • MS ACCESS DATABASE PROGRAMER
    Looking for an access programmer. Contract position. Send resume with references and rates to: [email protected] www.prospace.biz
  • PROGRAM MANAGER
    position in Phoenix with the Babbitt Center for Land and Water Policy.
  • ROADS END CABIN NEAR YELLOWSTONE
    Vaulted ceilings, two fireplaces, two bedrooms, loft, jetted tub, wifi. Forest, mountain views. Wildlife. [email protected]
  • ACCOUNTING CLERK
    Our director is seeking to employ the services of an Accounting Clerk to assist with various accounting and administrative tasks. This is a great opportunity...
  • EXECUTIVE DIRECTOR, COMMUNITY RADIO PROJECT
    Community Radio Project, Cortez, CO (KSJD & the Sunflower Theatre). Visit ksjd.org and click on the Executive Director search link. CRP is an EOE.