Pinyon Pine Mortality In Southern Colorado

by Kent Grant

CSFS

February 28, 2003

Continued from Last Weeks Press

A more practical means of treatment is to cut a band of healthy, green pinyons immediately surrounding a disease pocket. This eliminates the live roots needed to spread the disease to pinyons out beyond those that were cut. Sacrificing a few pinyons in this way can potentially save many more. Fortunately, black stain root disease does not infect juniper.

THINNING: Thinning pinyon-juniper woodlands can have substantial benefits. Thinning reduces competition for sunlight, nutrients, and moisture, hence enhancing the vigor of the remaining trees and making them more resistant to bark beetle attack. Because thinning reduces the amount of live root contacts beneath the ground, it can be beneficial in slowing the spread of black stain root disease. Reducing tree density will also significantly lower wildfire hazard, especially if the resulting slash (branches and tops) is lopped and scattered, burned, chipped, or hauled away. When possible, thin or prune pinyons during the late fall, winter, and early spring, since cutting during the warmer months when Ips are active can actually attract beetles. If thinning or pruning must be done during the warmer part of the year, the remaining pinyons should be preventively sprayed as soon as possible following cutting.

ADDITIONAL INFORMATION: An informative fact sheet complete with color pictures illustrating symptoms of Ips beetle, black-stain root disease, and other problems affecting pinyons can be downloaded from the Colorado State University Extension Service website at www .colostate.edu/Depts/coopExt. Select : information online ", then " insects ", then "fact sheets", then "trees and shrubs", and finally "Pinyon Pine Diseases and Insects, no. 2.948". For further information and assistance, please contact the Colorado State Forest Service.

Products: Carbaryl, commonly sold under the trade names Sevin, Sevimol, Savit, and carbaryl. (Use a variety labeled for bark-beetle prevention), and Permethrin (Use a variety labeled for bark beetle or wood borer prevention), commonly sold under the trade names Ambush, Astro, Dragnet, Perm-X, and Pounce. Follow label instructions.

Technique: Apply to living, high-value pinyon trees (aesthetically important trees near homes, businesses, recreation areas, etc.). From the ground, spray trunks and larger branches near the trunk to near top of tree where trunk tapers to less than an inch in diameter. If trees are tall, a motorized spraying unit may be necessary to reach the upper part of the tree.

Timing of Application: Can apply anytime during the warmer months, but it is best to spray in early to mid-April to insure that trees are protected when the first generation of the year emerges to attack new trees, At least one re-application in midsummer is strongly recommended to insure effectiveness later in the season. Three applications (on approximately April Fools' Day, July 4th, Labor Day) should provide maximum protection. Be aware that some formulations require monthly re-application - read the instructions for the product purchased).

Comments: Preventive spraying will not save pinyons already infested by Ips beetles, or pinyons infected with black-stain root disease. Although preventive insecticides can be purchased and applied by landowners, there are well-qualified and equipped arborists and tree-care companies that can be hired to do the job.

Chemical Control: There are no longer any pesticides labeled for treating beetle-infested trees. Lindane is no longer available, and according to the EPA, remaining supplies should not be used for this purpose.

Non-chemical Methods of Treating Infested Wood: Includes burning (in fireplace, woodstove, or outdoors), chipping, peeling soaking, burying, transporting to a safe-haul site at least a mile from pinyon trees. Solar treatment, with or without the use of clear plastic sheeting has been used for treating wood infested by other varieties of bark beetles (i.e., mountain pine beetle in ponderosa and lodgepole pine). Solar treatment is not recommended for pinyon Ips because of the short period of time between Ips generations.

Older Ips-Killed Trees: Only currently infested trees need to be treated. Beetle-killed trees with few remaining red needles, trunks riddled with a multitude of "exit" holes that look like small drill-bit holes or with no living Ips between the bark and wood. It is likely that dead wood insects such as woodborers, will be found beneath the bark, but these are not a threat to healthy, living trees.

A Note About Black-Stain Root Disease: There is no known chemical control for black-stain root disease. Other control methods are aimed at preventing the disease from spreading via root contacts beneath the ground. These include 18-inch-deep trenching if possible around disease pockets to separate the roots of infected trees from those of healthy trees. The trench is usually filled with some substance to keep it from refilling with dirt or cutting a band of live pinyons surrounding a pocket of infected trees, which kills the roots needed to spread the disease.

Juniper and Ips Beetles/Black stain Root Disease: Rocky Mountain and One-seed junipers are commonly called "cedars". They occur intermixed with pinyon pines in the woodlands of southern Colorado. Although junipers are not attacked and killed by the pinyon Ips beetle or black-stain root disease, they have their own set of biological enemies. Fortunately, these are not a significant problem in our area at this time. Thinning and Pruning of Pinyons: It is a good practice not to cut or prune pinyons during he warmer time of the year when beetles are active. Such activity can attract Ips into the area. Instead, thin or prune in late fall, winter, or early spring. If cutting must be done during the warmer months, preventively spray residual pinyons as soon as possible following cutting. Thinning of pinyon -juniper woodlands will reduce competition for sunlight, water, and nutrients, making the residual trees healthier and more resistant to beetle attack.

(Submitted with permission from Kent Grant, by Donna Davis, Colorado State Forest Service, La Junta Office.)