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Beetles continue advance into local forests

Posted: Thursday, Apr 4th, 2013


Mike Blakeman, public affairs specialist, illustrates a point about beetle kill, while working at his desk in the San Luis Valley Public Lands building outside Del Norte.


SAN LUIS VALLEY—According to Mike Blakeman, Forest Service public affairs specialist, the latest aerial surveys detect that 382,000 acres of a total 560,000 acres of Engelmann spruce and the sub-alpine are infested by Spruce Bark Beetles.

Blakeman noted that the aerial surveys are at least a year behind the actual spread of the beetle, so that is not the entire story because it takes more than a year for the trees to die once they are infested.

“Bottom line is that we can feel pretty comfortable saying there is more than 400,000 acres infested at the moment, which is basically 70 percent of the spruce/fir cover type,” said Blakeman. “It is hard to know for sure, but we expect all, or almost all, of this spruce/fir cover type to be infested with the next three to five years, with some isolated pockets that they might not get into.”

“What happens is that the beetles fly in and they bore in and start making these vertical tunnels and galleries, laying their eggs on the sides (of the tree) and when those hatch, the larvae eat more or less around the tree. They end up girdling the tree which stops the flow of sugars and nutrients from moving up and down the tree, which in essence, starves it to death,” said Blakeman.

It is a race to see what kills the tree first. A lot of these beetles also carry a fungus called the Blue Stain Fungus, which quickly gets into the sapwood, an area of the tree where water moves up through the tree in vessels, essentially choking it.

The beetles are hard to eradicate because they are safe underneath the bark and spraying is ineffective. There are different forest management techniques to deal with beetle outbreaks, which can be fairly successful.

Through timber management practices, the infected trees are cut down and the area is thinned out so that the trees left behind get more sunlight, which enables them to be healthier and protect themselves better. Seedlings are also planted after the dead trees are harvested in order to help start a future forest. This technique is being proposed in the Divide Ranger District, 15 miles west of Creede.

Another technique is to go in and cut trees down and “deck”, or stack them. Most of the beetles will fly in to those trees on the ground because it is easy and fresh food for them since they do not have to work as hard to get inside of the tree. The trees are left there for a while and then hauled off to the sawmill. This is called the “spruce beetle trap method.”

“Obviously we can’t do that everywhere because there are some places that we can’t get into, especially the wilderness,” said Blakeman.

The beetles are now in the Sangre De Cristos and Blakeman thinks that a big blow down there enabled the beetles to build up their populations in those areas rather than the epidemic in the San Juans moving from here to there.

The beetles are native and have co-evolved with the spruce tree and have always been there. Infestations happen when trees become weakened or old and are unable to protect themselves due to a blow down. The beetles build their populations in the blow down and then spread to other areas of the forest, overwhelming the tree's defenses with their sheer numbers.

The spruce beetle primarily attacks Engelmann spruce but it can also attack Blue spruce, which grows in slightly lower elevation. The forest service has seen evidence of Blue spruce being attacked also, but they aren’t expected to have as big of an impact.

Those trees may be safer Blakeman said because, “The Latin word for Blue spruce means pungent and that doesn’t sound tasty. Pungent? No I don’t think I want to eat that.”









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