Experts Stumped On Dying Pine Tree Problem

By MAGGIE MCMURRAY

Moapa Valley Progress

Many Moapa Valley homeowners have been noticing a problem with their pine trees. And the problem seems to be spreading. Usually healthy trees are developing dead branches at an alarming rate, often resulting in the loss of the entire tree. The problem is fast moving and seems to become more widespread by the day.

In an effort to figure out what is wrong, the local Northeast Clark County Extension office invited specialists to come to Moapa Valley and personally examine affected trees. Last week Nevada State Entomologist Jeff Knight and UNCE Horticulture Specialist M.L. Robinson traveled to the valley to meet with local horticulture specialists and UNCE staff.

The group visited several local properties with dying trees and discussed with homeowners what they have been observing. But hopes of an easily identified solutions didn’t bear out. The problem proved to be more complicated.

Most of the diseased trees were showing distinct signs of stress, similar to when they are not getting enough water. Even trees on drip systems were stressed and dryer than they should be. The group noted that the problem of dead branches was also found on trees that were flood irrigated and seemingly experiencing ideal growing conditions. This indicated that, although water may play a part in the problem, it does not seem to be the main cause.

Knight’s primary focus was to try to locate signs of bug infestations. He carefully examined live branches and dead, as well as branches that had been removed from the trees, but saw absolutely no sign of a bug infestation.
“Mostly I was looking for signs of the Mediterranean pine engraver, which is a relatively new beetle to Nevada,” Knight said. “We first saw signs of it in 2015 and it is spreading throughout Las Vegas. It loves stressed trees. They come in so thickly that you can see them flying into and out of branches.”
Knight said that he saw no evidence that the infestation had spread to Moapa Valley.

Many locals have postulated that the tamarisk beetle that was introduced several years ago to control the spread of tamarisk trees has spread and started attacking the pines. Knight said that this absolutely was not the case.
“Beetles are very specific to the specie of the beetle and the specie of the tree,” Knight said. “The tamarisk beetle only eats leaves (as opposed to bark or pine needles) and is very specific down to even the certain type of tamarisk it attacks. It is very well established that the tamarisk beetle doesn’t travel between species and what we’ve seen today also supports that.”

After touring many properties the group was unable to make an on-the-spot diagnosis, but pledged to continuing to study the problem. “We know that people are wanting to know what is wrong and what they should buy to fix things,” Robinson said. “The answer is they can buy anything they want but it’s not going to help their tree. Before anyone buys anything we need to ID the problem and that takes time and study. This is our first look at it. We can’t solve a problem this big in just a few hours, but it’s a place to start. We’re gathering information, which we’ll study and try to determine what we need to move forward from here.”

Property owners were grateful for the visits and the study the group put in at each stop. They spent considerable time with each homeowner, questioning them on plant history, watering practices, the age of the trees, and so forth.
They noticed in some cut branches and stumps that the tree rings from recent years are much much closer together than the rest, which is indicative of drought conditions.

Logandale homeowner Virgil Hardy pointed out to the group that the dead branches showing up in his trees were almost exclusively on the west side, hypothesizing that drought conditions combined with excessive afternoon heat and sun may be causing heatstroke in the trees, which in turn is causing them to stress and die off. The group acknowledged that this certainly could be a contributing factor, but is probably not exclusively responsible.

Homeowner Tracey Thornton hypothesized that there was maybe a change in the irrigation water since the reservoir was drained and relined last year. The group agreed that there may be something to that idea as well. But that wouldn’t account for the dying trees that are watered off of culinary water, they said.

Regardless of cause, most homeowners are just looking for answers. “I’m tickled pink that they would come out and look at my trees,” Hardy said. “I’m grateful for their time and effort. I hope we find some answers soon.”
Thornton agreed, saying, “It’s an ongoing problem, but it is not just my problem this year, it’s everybody’s. It’s not hit and miss anymore, it’s all over. I’m hoping we can stop it from spreading more.”

In the meantime, both Robinson and Knight recommend removing the dead branches from the trees by cutting them off several inches into the green and then to get those branches off the property or to burn them. They added a reminder that it is very important when trimming branches to sterilize your cutting implements such as clippers or saws between trees or you might be spreading the problem from tree to tree.

For more information, contact the local Cooperative Extension at 702-397-2604.