Upper tops of conifers dying

davidwyby

Desert Beaver
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Apr 25, 2022
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El Centro, CA (East of Sandy Eggo)
Been a hot summer. Lots of trees down in the desert look singed. Up in the mountains I keep seeing scattered conifers, probably ponderosas with just a bit of the top dead. This one is a lot more. Wonder what’s doing it.

IMG_8669.jpeg
 
Beetles are the natural preditor in their environment. They are always there. Once trees get stressed from drought, or fire; they can't defend themselves as well. Too much warm weather, the beetles hatch more broods yearly overwhelming even heathy trees. Cold snaps are what set them back. Freezing cold. Then wet and snowy winters.
 
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I have had beetles in my pondo at least a couple times. Seems they were scattered in the limbs thru the tree and gradual. What I’m seeing up yonder is Bam fast whole top of tree dead, rest untouched. The one in the pic isn’t a good example. Maybe they work top down and this one is just further along. Also, how far are the killed trees usually apart? These are pretty spread out.
 
There is more than one kind of beetle and attack the tree differently.
A dead top could be two different species. Depending. For instance, the western pine bark beetle will attack the tree at about 1/2 or 1/3 up the tree. The larvae will girdle the cambium with their little burrows and kill the top. Or, the whole tree is dead and doesnot know it. It slowly depletes its stored nutrients. Top dies first. Then bam, whole tree brown quick.
There are bettles that just hit the tips, tops, roots, root flare.....
 
Often, bark beetles will attack a single weekend tree, and once it's dead, they'll evacuate to the neighbors and attack them, even if healthy. Thus beetle kills are often little clumps, and if nothing checks their progress like a hard freeze or some hillbilly with a saw, the clumps can become whole stands of treed decimated, as has happened in many places across the Arizona forests.

Once targeted, individual trees don't have much hope. The beetles produce a pheromones that draw more beetles to the tree, meanwhile, the tree itself is producing stress chemicals that also draw in the beetles. This sets up a feedback loop that dooms the tree. There's a few insecticides that work, but only during a narrow window at the start of the infestation, beyond that, the tree is too far gone, and the beetles too numerous.

That said, most trees (especially pines) have bark beetles, but the numbers are low enough for the tree to withstand the seige, but when something happens to compromise the health of the tree, it can no longer keep the beetle population down and their numbers explode.

Keep in mind that many species of bark beetle, have a symbiotic relationship with the blue stain fungus. BSF has the effect of weakening the wood, making it easier for the beetle larvae to munch through it, and the beetles continously carry the fungus to new hosts. BSF softens and en-brittles the wood, which can compromise the integrity of the tree and create a dangerous situation to the faller in extreme cases.

Our protocol when dealing with beetle kills, is one of quarantine. Affected trees come down immediately, and are immediately removed to the brush pit. If for some reason, the material cannot be removed at the time of cutting, it's piled on a tarp, covered with a second one, and fumigation begins using a few bug bombs. Alternatively, the material is burned as quickly as possible. Any tree in the near vicinity that looks at all unhealthy is recommended for removal as well, to reduce the risk of missing an early infestation, and the whole cycle repeating itself.

We always recommend that bark beetle infestation be treated with extreme aggression. Any potential victim should be removed post haste. It's also more cost effective. Rather than going back to the same location over and over, taking individual trees as they croak off costs the homeowner much more than taking everything at once. Multiple trips means everything is bid as a separate job, with all the margins that entails, bidding everything as one big job eats up a lot of those costs.
 
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