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Spruce trees turning brown? Here’s what might be going wrong

Spruce aphids have stripped needles from trees near Marian Beck’s Saltry Restaurant in Halibut Cove. Photographed Sunday, May 15, 2016. (Charles Wohlforth / Alaska Dispatch News)

Right now, I am getting questions about spruce trees. Lots of them. More specifically, yardeners are concerned about needles turning red and dropping off. Here is another reason why I wish we still had our Cooperative Extension office in Anchorage. (Did you email the Regents?) Unfortunately, I am not a pest scout, and even if I had the training, it is pretty hard to give an answer from an emailed photo.

So, since we don't have an Extension pest scout anymore, it's necessary for you to do a bit of research on your own so you can figure out what might be going on. Let me help: If you think there is something wrong with one or more of your spruce, check out this guide from the state Department of Natural Resources at on.adn.com/2fDP4qD. It's a great starting point.

The problem in asking me is that there are all manner of reasons why a spruce tree would have needles turn brown, from sawflies and budworms to fungi, viruses, mites and bad weather. I have noticed a few things in general, however.

First, most spruce trees will loose up to 10 percent of their needles annually. They turn brown first. There is nothing you can do about it.

Next, spider mites can turn a blue spruce red, so to speak, but these usually come out when it's dry or when we have a drought. That does not seem to be the case this year. However, it is easy to spot spider mites with a hand lens. The webbing they create often holds detritus and you will notice it. Just for giggles, take a white piece of paper, hold it under an affected branch and shake it — the branch, not the paper. You should be able to collect mites if they are there. And if they are, an application of dormant oil this time of year should smother them.

Note that mite attacks impact the whole tree. Many people are complaining about losing only inner needles, so these trees probably have something else going on, most likely some form of fungi. The most likely listed in the internet literature is called Rhizosphaera needle cast. The dead zone is all in the inner area of the tree, starting closest to the trunk. The needles display neat rows of black dots. The needles won't grow back and the tree will look sparse. There really isn't much you can do in these parts in terms of spraying.

Then, of course, there is spruce bark beetle damage. It is baaaaack. In fact, it never went away. Affected tree trunks have a few characteristics: distinct borings where the insect entered the tree; sap flows where the tree tried to protect itself; dust at the trunk; and, ultimately, a dead tree. The increased incidents of these infestations is a direct result of warmer springs along with earlier and more frequent freeze-thaw cycles.

Finally, spruce aphid (Elatobium abietinum) has become a real problem, especially down Homer way, but it is moving up, I am sure. Again, the infestations are a direct result of our climate getting warmer. If there is any Alaskan who is a climate denier, then they simply don't have their eyes open.

In general, there are only a few things you can do to help your spruce trees. First and foremost is to treat them well. This means being extremely careful with weed-eaters, mowers and tractors. It means giving your lawn water when we are in dry seasons. Mulching with a tree's own needles is always a must and not compacting soil around the roots is extremely useful.

Second, make sure air can circulate. This may sound silly, but many spruce trees have boughs to the ground. Several arborists suggest carefully removing bottom limbs up to as high as 6 feet or so. This allows wind currents to get under and into the canopy.

The careful way to remove limbs, incidentally, is to make a cut through the bark UNDER the limb first and then cut into this from the top. When the limb breaks, it won't peel off bark. And, do not cut flush to the trunk. Leave a "collar," a bit of the limb, so that the tree can form a scar and heal the cut.

Jeff's Alaska garden calendar for the week of Sept. 22

Bulbs: If you want spring flowering bulbs, now is the time. Get out and plant as many as you can! Take a class on Sept. 25 at 12 p.m. and Sept. 29 at 8 p.m. "Bulbs for Beginners" at the Alaska Botanical Garden. Free. (alaskabg.org/event)

Mushroom Walk: Sept. 28, 6-7:30 p.m. at the Alaska Botanical Garden. Join Chitin Anderson and learn mushrooming. Price is $12-15 depending on membership. (alaskabg.org/event)

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