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New Mexico State University

New Mexico State University

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Piņon Protection: Battling Bark Beetle No Easy Task

LAS CRUCES - A multiyear drought and an army of bark beetles have launched a brutal attack on New Mexico's revered piņon trees, setting the stage for a massive die-off, increased wildfire danger and dearth of the tasty little nuts. Huge patches of brown piņons splotch northern New Mexico hillsides, as the voracious beetles kill off drought-stressed trees.



Carol Sutherland, an entomologist with NMSU's Cooperative Extension Service, points to a bark beetle entry point on an infested piņon tree. The B-B-sized pests, which are causing a massive piņon die-off, attack the tree's water-conducting tissues beneath the bark. (03/04/2003) (NMSU Agricultural Communications Photo by J. Victor Espinoza)

"Homeowners, landscapers and pest control operators are expending considerable effort in fighting bark beetles attacking our New Mexico state tree, the piņon," said Carol Sutherland, an entomologist with New Mexico State University's Cooperative Extension Service. "The battle won't be easy and many people may work long and hard to save their trees, only to lose them suddenly."

But New Mexicans' piņon pride makes it easy to succumb to bogus cures touted for controlling bark beetles, Sutherland said. "Before using some new or so-called miracle chemical that may or may not be registered or even appropriate for use on these pests, step back and ask an Extension expert," she said.

These B-B-sized beetles are tree killers, Sutherland said. If a tree is infested with them, you're already losing the battle and have a good chance of losing the tree, to the beetles directly, to a fungus they carry - or both.

The bark beetle outbreak is part of an ongoing natural disaster rooted in persistent drought. As the state has suffered through historically dry conditions, bark beetle problems have compounded with each parched season, Sutherland said.

Piņon trees or other pine trees that have reddish-brown or yellowish-brown foliage are dead and should be removed promptly, not only to improve landscape appearance but also to reduce wildfire danger, Sutherland said. Meanwhile, homeowners who still have trees left may face hard choices later in the season because of watering restrictions.

Thinning a stand to the point where it can be sustained by available resources may be necessary, Sutherland said.

"Where bark beetles and other wood pests are concerned, the best defense of susceptible trees is a good offense," Sutherland said. "Piņons that have been well watered and well cared for over the years have the best chances of repulsing a bark beetle attack. But where bark beetle populations are very large, they can overcome the defenses of even healthy trees."

Homeowners who want to save their piņons can use any one of several insecticides appropriately labeled for exterior treatment, she said. However, systemic insecticides haven't been effective in the past, primarily because the affected tree's water-conducting tissues, which are right under the bark, have already been damaged by the beetles.

"You need to understand the limitations of these insecticide tools," Sutherland said. "Once the beetles are inside the bark, spraying the exterior doesn't affect the beetle larvae survival. Systemic insecticides haven't been able to rescue the stricken trees either."

The only thing likely to stop New Mexico's bark beetle outbreak is the insect's own natural population life cycle in which the pests build up to such a number that they saturate their environment, Sutherland said. "Then when there's no food left, populations crash," she said.

Although forestry officials know that extensive areas of piņon trees are affected, Sutherland said she has examined several piņon stands in northern New Mexico where every tree has died from beetle damage. In addition to the decimation of thousands of piņon trees, ponderosa pine and mixed conifer forests at higher elevations are also being assailed in different parts of the state, but by different species of bark beetles.

"Bark beetles can literally smell trees that are under stress," Sutherland said. Once a few successfully bore into a piņon or other host trees, they send out a chemical signal that attracts hundreds to thousands of other beetles.

"Once the trees start to die, there isn't much you can do," Sutherland said. "The only solution is to cut down the tree, and get rid of it and the beetles inside. This is your best chance to minimize the risk of beetle invasion from spreading to other landscape piņon trees."

At least some wood can still be used as firewood, if the logs are stacked in the sun and securely covered with landscape plastic for several weeks to kill the beetles, she said.

The beetles also carry pockets of yeasts, bacteria and fungus on their bodies, she said. For instance, blue stain fungus spores, which germinate inside the tree, can cause an infection that quickly blocks the tree's water-conducting tissues, killing it if the beetles already haven't.