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Tree RX: Don’t let pesky bugs get to you

An invasion of Ips beetles can kill a piñon in a few weeks. A prolonged drought has left most trees in the state stressed and vulnerable. (Courtesy of A. Steven Munson/USDA Forest Service/Bugwood.org)

An invasion of Ips beetles can kill a piñon in a few weeks. A prolonged drought has left most trees in the state stressed and vulnerable. (Courtesy of A. Steven Munson/USDA Forest Service/Bugwood.org)

ALBUQUERQUE, N.M. — Those rice-grain size bark beetles that decimated the piñons about 10 years ago are back, hungrier than ever. And they brought their friends.

“A lot of places are getting hammered again,” says state entomologist Carol A. Sutherland at New Mexico State University. Years of drought are taking their toll. “If we ever had a regular year, trees would be able to defend themselves. But if you’ve been out hiking, you know we have a lot of stressed trees and a lot of beetles. We have so many beetles, even with a healthy tree, the number (of insects) is so large, that they could overwhelm its defenses. Imagine lions and one cape buffalo. The buffalo never had a chance.”

Tiny Ips bark beetles have such keen detection ability, they can even smell out a tree that has just been pruned or has some other non-fatal injury, she says.

Or killing one piñon, they sniff out a nearby piñon tree and munch on it, even if it’s not as stressed as the previous host tree.

When the infestation occurs, it can happen so fast, homeowners can go on vacation and come back to a dead tree.

Sutherland has more bad news: other species of bark beetles, who like other trees such as Ponderosa pine, other conifers and even broadleaf trees, are also on the hunt.

Bernalillo County Horticulture Extension Agent Cheryl Kent says the majority of her beetle reports indicate the metro area has twig beetles on the rise. Those beetles favor end branches: “It’s not the death sentence for the tree that bark beetles are,” she says. “Thinning and pruning projects this summer encourage beetles to infest trees. The take-home lesson is if you have thinning or pruning to do, do it in the winter.”

Although each species has a favorite part of the tree and may have slightly different gender responsibilities, it all starts with a sneak attack, Sutherland says.

In a balanced environment, Ips bark beetles help recycle dead and dying trees, but when the population of beetles explodes, even healthy trees are vulnerable. (Courtesy of William M. Ciesla/USDA Forest Service/Bugwood.org)

In a balanced environment, Ips bark beetles help recycle dead and dying trees, but when the population of beetles explodes, even healthy trees are vulnerable. (Courtesy of William M. Ciesla/USDA Forest Service/Bugwood.org)

For the Ips beetle, it starts with a lone male who manages to bore through piñon bark without getting smothered and stopped by a deadly dose of piñon sap, Sutherland explains. He creates a “nuptial chamber,” and then exudes his own welcoming fragrance to attract females.

Each female beetle carves her own egg gallery parallel to the grain of the wood. When the larvae hatch, they mine their own lateral trails under the bark.

“It looks like a feather,” Sutherland says of the pattern the beetles make. It effectively blocks the transfer of nutrients from the leaves and the roots.

Many of these beetles carry fungi, blue or brown stain, that further weakens the tree, further clogging its vascular system. “If the bark starts peeling, then you’re in trouble. But if you peel the bark back, it would look like someone made the marks with their fingernails.”

Otherwise, because the bugs are so small, detection is difficult: “Maybe if they’re lucky, a homeowner sees a little sawdust in the crotch of some branches,” Sutherland says. But even then it may be too late to save the tree because of the beetles’ systematic destruction.

Sometimes the only solution is to take down a dead tree and haul it off so its scent can’t attract more beetles to other healthier nearby trees, Sutherland says.

Galleries or trails left in a piñon by bark beetles damage the tree’s ability to move nutrients. (Courtesy of William M. Ciesla/USDA Forest Service/Bugwood.org)

Galleries or trails left in a piñon by bark beetles damage the tree’s ability to move nutrients. (Courtesy of William M. Ciesla/USDA Forest Service/Bugwood.org)

Some area tree companies offer micro injections of pesticides to the tree to try and stop the bark beetle attack, but Sutherland says the infestation is often too far advanced for that remedy to work.

Prevention means proper planting in the first place and adequate moisture for the trees, Kent says. A deep monthly watering is best with a soaker hose stretched around the circumference of the tree’s drip line, the edge of the branches’ extension.

But no one knows if a boulder lies under the tree’s roots or if some other factor, including New Mexico’s dry, windy climate, stresses the tree beyond salvation.

“The 2011 freeze didn’t help anything,” Sutherland says. “It may take years for symptoms to develop. The point is, you can do everything right and still lose a tree.”

If your tree dies from bark beetles or their cousins, you need to remove the entire tree, experts recommend.

Kent adds that trees attacked by twig beetles may survive with most of the tree intact, but that pruning out the dead branches should wait for winter to avoid attracting more pests.

“There’s a lot of luck involved,” Kent says. “A lot of it is nature doing its thing.”

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