Tuesday, April 24, 2018

Pine needle what? (Keeping your coniferous antenna supports alive!)

The afflicted tree:  The needles are more normal at
the top, but looking rather "thin" farther down.
Because of the number of pine cones, the tree
looks "browner" in this picture than it really
is - but it is definitely under stress!
Click on the image for a larger version.
Late last year I noticed something amiss with a fairly large (50 foot/15 meter tall) Scots Pine tree in my front yard:  The needles looked a bit "thin" and short.  In the past this tree would tend to shed needles and pine cones all over the place on a seasonal basis, so I kind of ignored it over the winter - but this spring, when I started yard work again, I became concerned.

Something was definitely wrong with this tree.  While the needles themselves seemed to be green and flexible, I noticed that at the top of the tree they looked normal-ish, but the bottom 2/3rds of the tree looked "skimpy", so I decided to investigate more closely.

If you've followed this web page you've probably figured out that while I'm probably not a yard and garden person, I do what I need to do to keep the yard in reasonable shape, asking my Dad or friends for advice when something wasn't quite right.   A couple of weeks ago I finally did what I should have done months ago:  Take a very close look at the tree.

On the lowest branches - where the problem seemed worst - I could tell that the limbs were very green and flexible - but the needles themselves, while green, were thinner than they should have been - and were covered with small spots.  Doing what many people do these days I resorted to Google and it "told" me about all sorts of possible fungal infections and other things - but I wasn't satisfied that it was describing what I was seeing, so I asked a friend of mine who'd had tree work done in the past year or so.  He referred me to the guy that did his tree work - a "semi-professional" who did this as a combination of a hobby (I gathered that he really likes trees!) and a second job.

After a couple weeks of phone tag, I was finally able to talk to him and I described what I was seeing.  Almost the first thing he asked was "Do the spots scrape off?"

"What?" I thought.  "Those are probably small bugs" he continued.  I must admit that it never once occurred to me to try scraping them off - and it then I realized that I should have looked at the needles with a magnifier.  He continued to explain that he suspected that the tree was suffering from "Pine Needle Scale" - an infestation of small insects that feed on the sugars in the needles - and this would probably kill the tree if left un-checked.  He then explained that he could probably drive out to my house and charge me a chunk of change to tell me this same thing in person - and then charge me more to treat it, or he could just save himself some time and me some money and have me treat it myself.

A close up of a bough on the affected tree.  As you can see, the needles are a bit shorter and thinner ("thin" like paper rather
than in number) and paler than they should be - and there are lots of spots!
Click on the image for a larger version.

After a few more minutes detailing the common treatments, we got off the phone and this time, armed with more definitive information, I did a bit of online research and what I saw in the pictures looked very much like what I'd seen.  It wasn't until I got home and plucked a few needles off the tree and looked through a magnifier that I saw that these spots were, in fact, small insects - looking exactly as he described and much like the pictures on the web.

A close-up of one of the needles showing the infestation
of what are probably Chionaspis pinifoia - little, hard-shelled
insects that literally suck the life out of the tree!  These will scrape off
with a fingernail revealing more-or-less normal looking needle
underneath - except that it's wet with weeping liquid from the tree.
Click on the image for a larger version.
I have two other pine trees in my yard that look healthy - so I inspected them, but the results were inconclusive:  I saw nothing obvious, but I didn't check everywhere within reach. If they were infested, it wasn't bad... yet...  A more thorough inspection has revealed that both of the trees in the back yard are infested - but it appears to be mild as I had to look a bit for them.

Why did the tree in my front yard get infested but the others not as bad?  I have a suspicion:

Two years ago, during the installation of a solar power system, it turned out to be necessary to upgrade the utility power connection to my house, so a narrow, 48" (122cm) deep trench was dug through my front yard - but the path took it very close to this same tree.  When the trench was open I could see that there were several rather large roots that had been cut - and this concerned me a bit.  What I suspect happened was that this weakened the tree a bit, making it more susceptible to an infestation - but then again, it could have just been bad luck!

Between talking to the tree guy and going online, I read about three common ways to control these critters - typically Chionaspis pinifoia (read about this insect at the "Tree Geek" web site).  These methods include:
  1. Spraying with an insecticide.  This is the "kill them right now!" approach - but it may not get the entire tree (particularly if it is a tall tree that is difficult to spray in its entirety) and this is most detrimental to beneficial insects like bees, ladybugs and other things if they happen to be on the tree, downwind, or very nearby.
  2. Ground soak.  A solution of insecticide and water is poured (usually in a small "moat" to confine it) around the base of the tree so that it is quickly absorbed into the root system.  This systemic treatment is slower to take effect, but is longer lasting and will protect the entire tree - and it is somewhat less harmful to beneficial insects since it is more or less confined to the tree.
  3. By injection.  If the tree is in really bad shape, insecticide is injected directly into the tree where it can more-quickly be taken up.  The "tree guy" with whom I was speaking seemed to think that since I didn't (yet!) have large sections of die-off that this wouldn't be necessary.
There are more ways to deal with these things that are less harmful to beneficial insects - but the general opinion seemed to be that these were best for preventing infestations, controlling those infestations that were minor, or in those situations where there was a need to minimize the effect on the "good" bugs (e.g. to protect pollinators, etc.)  For trees that were under significant stress, arborists seem to recommend the "strong" approach where it can be safely done.

Based on what I read, my tree wasn't in "really bad shape" since the needles - while getting a bit pale - weren't dying off in large quantities... yet - but it is under a fair amount of stress.  Apparently, it is about this time of year (April, May) around here that these bugs start to reproduce and become more active - so this is the time to do the treatment.  I decided on a combined approach:  Spraying where I could reach and doing a ground soak around the base.

To this end, I sprayed the tree on a wind-less day as far as I could reach with a solution of "Sevin" (a carbaryl inseciticide):  I was able to get the bottom 1/4-1/3 of the tree, which encompasses about 1/3-1/2 of the pine needles.  Because of the height of the tree, I couldn't really go much higher than I could reach via the spray while working from a free-standing ladder - but this would, at least, have an immediate effect on a significant part of the tree.

The second treatment is a ground soak (an imidacloprid-based insecticide) as described by the "tree guy", the guy at the local farm supplies distributor from whom I bought the stuff, and the online descriptions:  This latter application will take a couple of weeks to work its way through the entire tree - but it is, by all accounts, considered to be very effective.  While I'm at it, I'll also proactively treat the other two pine trees in my yard with the ground soak - just in case those critters managed to get around - however they do that.  Based on what I have been told and what I have read, this treatment will become an annual, spring ritual.  Since pine trees are less attractive to bees than other plants, I'm hoping that the effect on them will be minimal - although they may collect some components of propolis from them.

So, the next few months will be telling.  I really do like my pine trees:  I think that they look nice, they offer a bit of cooling shade to the house - and they provide nice anchor points for my ham radio antenna!

* * *

Update - 6 June, 2018:

It's been about six weeks since treating the tree - and it is no worse off, but the bugs are still hanging on, so I went a step further as recommended by an expert:  Treating the tree with "Safari 20SG" - a Dinotefuran-based insecticide.  According to available information, this insecticide is taken up by the tree more quickly and is more effective at eradicating parasitic insects.  Hopefully, once these bugs are knocked down, the tree will recover and will be able to better-resist them in the future.

The instructions indicated that 1.0-2.2 oz were recommended for every 10 feet of tree height, so for a tree of this size (about 55 feet tall) the entire 12 oz container (which cost about US$110) was dissolved into several gallons of water and poured around the base using "soil drench" techniques.

Update - 27 June, 2018 - Success, I hope:

 About a week ago, I examined the tree again and saw that the bugs were rapidly dying off:  In fact, it was difficult to find a live one.  This die-off must have started happening a week or so before this as the needles are already looking "plumper" and slightly more green - a sign that fewer of these things are still trying to suck the life out of the tree!

There are still a lot of these things covering the needles even though they are dead, but at least some of them should weather off - and all of their carcasses will eventually fall with the needles as the tree replaces them in its normal cycle.

Update - August, 2019:

The bugs have remained dead and the tree is looking much more healthy, once again in the process of producing pine cones.  From what I have read, it takes about 3 years for this type of tree to completely replace its pine needles, but new needles are easy to spot - partly because they don't have the carcasses of bugs on them!

It looks as though a simple ground soak of an imidacloprid-based insecticide has halted the (mild) infestation of the trees in the back yard - but from what I have read and what I have been told it will be a constant vigilance going forward as one can never really get rid of them completely, mostly likely due to the fact that there is always the potential for re-infestation from wherever these things came from in the first place!

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This page stolen from ka7oei.blogspot.com