Spider Mite Arborvitae Decimation

Updated — Originally Published June 8, 2011

Last spring and summer were brutal for landscaping in New Jersey… almost zero rain and non-stop heat in the nineties. I had a line of emerald green arborvitaes that had been growing beautifully for about 8-9 years. These got hit really hard, and I frankly never saw it coming. I thought they were so well established that there was nothing to worry about, but it seems I was completely wrong. This is how I learned a very hard lesson about spider mites. I managed to get rid of them with a mite control spray, but I lost quite a lot before I did.

Signs of Spider Mite Damage

Some of my trees started showing signs of distress – losing their deep green color and tending toward a sickly golden yellow/brown. What I thought was particularly weird was that several of these were adjacent. I casually mentioned this to a landscaper I met at a friend’s party, and he said he’d seen entire rows of arborvitaes wiped out by spider mites in the previous couple of weeks. I think I responded… “Uh, what?” I never heard of anything like this before, and the thought of losing 23 eight-foot-tall arborvitaes was more than a little hard to swallow!

So, knowing little more than these bugs were some kind of “mites” that quite possibly resembled “spiders,” I got up the next morning armed to test the trees. Spider mites are almost too small to see, and they can thrive in extended periods without rain. We’ll get more to that later, but for now – I just wanted to know if these things were killing my trees, and if so — how the heck to make it stop.

Testing for Spider Mites

There’s a “white paper” test you need to perform, and it’s very simple. You go to one of your trees with a sheet of clean white paper and shake the tree above the sheet. Then you study it closely in bright light. What will be immediately obvious are small pieces of plant material on the paper, but upon closer inspection you may see some very small bugs. These aren’t spider mites – they’re just bugs.  ;-) You have to look even closer — find the tiniest black specks you can see (and what you may think is part of the paper initially)… focus on these. Find two or three, and see if they start to move relative to each other. If you can find these – here are your spider mites.

Some Research, Analysis & References

Once I found my moving black specks, I didn’t research anything at all – I knew the clock was ticking and so I ran right out to the hardware store and consulted on the best treatment. Naturally, I came home with bottles of chemicals – and started spraying the line of trees. I sprayed again after a couple of days, and then I waited. A few more died over the next 2 weeks or so, and then it stopped. In the end, I lost 9 out of 23. There are photos of my entire saga below along with a description of each step of the process, but before we get there let me summarize some of the facts so you’re better prepared.

Spider mites aren’t insects – they’re really much more closely related to spiders: eight legs.

They’re incredibly small, less than half a millimeter when fully grown. (This is less than about 1/50 of an inch.) So they’re visible to the naked eye — but you *really* have to look very carefully. (And you really have to have good vision!)  The spruce spider mite is considered one of the most destructive spider mites in the US – and it particularly likes to feed on variations of arborvitae, juniper, hemlock, pine trees, blue spruce and Douglas fur. These are, of course, some of the most popular landscape evergreens in many parts of the US – and certainly on my property.

Theses mites, in general, damage plants by piercing plant cells and sucking out the fluids. They thrive in the spring and fall, not the summer. However – it takes some time for their damage to become evident on certain evergreens… so by the time you see your arborvitaes looking sickly (like in the heat of summer) the majority of cellular damage from the mites has most likely already been done.

The key, it seems to me, is the rain… One of things these mites cannot handle very well (which is very thankfully low-tech) is being knocked off the plants. They don’t have wings and they have very soft bodies – so, a good heavy rainfall (or periodic blasts with your hose) can go a long way in being a cheap and effective preventative treatment.

The spring prior to my arborvitae decimation — almost zero rain.

The intense heat of the summer (while doing nothing to help the spider mites do further damage), caused the trees themselves further stress after they had already been [invisibly] under attack for several weeks prior.

There are a few very good sites I found to fill-in these information gaps for myself (after the fact) that I want to convey here as well. Check out any of the following for much more background. They’re all exceptionally good:

Spider Mite Control & My Saga In Pictures…

So, I go to the hardware store and convey my story. The bad news was that I was likely to lose more trees (for the reasons explained above) – but the good news was that there was a spray to kill the mites on the trees. Many of these sprays are essentially oils that smother the mites; you’ll most likely connect the bottle directly to your hose and spray an auto-mixed combination of oil/water directly onto your trees (or plants/shrubs).

As this all played out, I did lose 9 of my 23 trees.

I ripped the dead trees out with my truck and a 12-foot chain (which, I have to say, was the only part of this miserable ordeal that was fun) – and then in the fall, I planted replacements – which was no easy task for one person with trees this big/heavy. If you want to try this yourself, I would strongly recommend reading Tree Planting 101 – and if you want to hire a contractor to help, please check out Hiring the Best Local Contractors and/or visit the Find a Local Contractor page on this site.

Here are two shots of the dying trees after the spraying. I was hoping the remaining sickly-looking trees would recover. Did they? Of course not. They got ripped out 2 weeks later as well after they were completely dead.

Spruce Spider Mite Arborvitae Damage 1

Spider Mites - Arborvitae Damage 2

The next shot is of a partial pile of my dead trees after being ripped out – waiting for me to cart them off to the township brush recycling center. They’re now mulch at someone’s house somewhere.

Dead Arborvitaes

Below is my truck at the recycling center, and I only put this in here for one reason: If you ever do something like this, be sure to have bungee cords to strap this all down. I have the cords removed here as I was about to unload the truck. But you definitely don’t want to drive anywhere with a load like this unless it’s securely tied down.

Arborvitaes to Township Brush Recycling

Replacement trees are then delivered in mid-October: a great time of year for tree planting. Note though: each of these easily weighed 100-125 pounds or more – almost all ball-weight. The delivery crew used a hydraulic platform to lower the trees onto my driveway. It’s deceiving. Don’t underestimate how heavy this type of work can be – you can easily hurt yourself if you’re not careful.

Note the hand truck I was using in the background.

Replacement Arborvitaes

Digging the holes to the appropriate depth and diameter

Planting Replacement Arborvitaes

And the final arborvitae line re-planted. I like to keep the nursery markers on the trees in case anything dies; I’ve always felt that in addition to a receipt – having the original markers on the trees can make a return/exchange all the easier. And I’ve definitely utilized this in the past.

Replanted Arborvitae Row

A Final Tip for Dealing with Spider Mites on Plants

I won’t get hit with this surprise again. The main take-away for me was essentially this: If there’s a spring without rain, blast the trees (and plants and shrubs) with the hose once a week or so. Don’t just “water” them as usual – hit the leaves with the intent of launching a swarm of near-invisible plant parasites clear off! It’s definitely personal.

And One More Final 7/19/15 Update Tip…

It’s been about four years since I originally wrote this article, and I’m happy to say that I’ve maintained the Arborvitae line in total; we haven’t lost a single one since then. But it’s so critical to be proactive – that’s become crystal clear to me. I have absolutely used the Bayer Insect Disease and Mite Control treatment multiple times now (more than just the hose alone) since the “great decimation” and best I can tell – it simply works. But again, you have to catch the trees before the death spiral takes hold. As I just mentioned to one reader in the comments below, I applied this treatment as recently as 3 weeks ago when I realized it hadn’t rained in a long time, and I thought the trees might be starting to look a little ‘funny.’ They’re nice and green today, and it’s now mid-summer. Best of luck to anyone who is reading this article, and if anyone has additional insight to provide – I would truly encourage anything that can be added below. This was a very rough experience, and even today (as you can probably tell) – I’m still pretty skittish!

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  1. eloise serna says:

    hello I’m having a problem with my arborvitae turning brown. It looks bad – may lose the tree. Also noticed tiny pin holes down the bark of the tree. Did the white paper test for spider mites also tiny bugs fell. Do I have to pull tree? It’s over 25 feet tall. I have 3 big trees, the others have no holes and are doing good. What to do?

    • Hi Eloise – I would recommend you take some pictures and go immediately to a local nursery to show them and get their opinion. Truly as soon as possible. With a tree that big, and especially in consideration of additional adjacent trees – I would not wait to have a local expert run this down. Photos will surely be critical. Best of luck to you. I really hope you can save your trees.
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  2. Patti Atchison says:

    I have the same problem. I had 7 I planted that were doing great but we got 5 more that looked bad when they went in. (long story….my husband and son were “helping” and got a deal….). Within a month all 5 looked horrid and in 6 months I lost them and then my original plants which are not 8 feet and full began failing. I thought it was a fungus and sprayed for that but nope, they are on a death spiral. I will likely lose them all. But today I will go get spray and try to see if we can fix this. Darn those holes were so hard to dig and the trees were so huge that I am bummed.

    • Patti – I so, so truly feel your pain. And I really hope for the best, if it’s possible to save your trees at this stage. If you’re anywhere near me (in New Jersey), the deluge of 2 days ago may have helped somewhat… not to restore the trees, but to wash [pound] away some of the infestation at least. All the best to you, and be sure you get help planting the replacements because as you’ve said, those holes are big and those trees [especially at 8 feet] are going to be extremely heavy.
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  3. Hi Mark, I am so glad I found your article. I have 23 6ft-Arbs that had just been planted five months ago in April. The trouble sign started about three months (beginning of July) after they were planted. I contacted the nursery that I got the trees from, since this year is particular hot and dry in the Northeast, they told me I didn’t water them enough. So I have been watering the Arbs 60 mins a day according to their advice. You won’t believe our water bill the last couple months! However, the Arbs are still showing trouble signs and three are in a dead spiral. Then I found your post! I ran (literally…) to my nearest home improvement store and got Bayer Mite Control as your suggested and soaked all my Arbs with it. I will do another application in 30 days as suggested on the Bayer instruction. Hopefully, this will stop the problem and save the rest of the Arbs. Thanks again for such a helpful info! I am very grateful!!! – Lee

    • Wow – this is incredibly similar to my experience, and I definitely know the pain and crisis you’re describing here, Lee. One additional thought, and I’m sure you’ve probably already considered this – but if the trees die, you’ll very possibly be under warranty from the nursery. It’s good you’ve been in touch with them. Are they perhaps close enough to stop by and have a look themselves as well? They might be more than willing, and the more they’re involved – the better things may go overall. Best of luck to you, and I really hope your Arbs make it; this is really just so, so painful to go through.
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  4. Mark S. says:

    Mark – (I’m also Mark!) so glad to have found your article today! I’ve been living the emerald thuja nightmare for the last several years and hope this “MITE” be my problem! My garden center guy informed me that emeralds will die after a few years growing in shade – even articles I’ve read confirmed this ….. however, my neighbor’s emeralds – also growing in part shade – don’t have this problem! Other articles scream of “Arborvitae leaf miners” – but I see no evidence of them. My emeralds have been hanging on with generous mulches of compost and occasional douses of “Miracid”, but, short of that… they are still “circling the drain”. I’ll try the Bayer miticide and see how this works out. Hope I can save some of the long-suffering shrubs! Thanks again! Mark S.

    • Hi Mark –

      I am so sorry; I totally missed your comment when you posted it in May, and I just read it carefully this morning. Have you had any better luck? One additional thing I’ve noticed with numerous trees and shrubs over the years is that sometimes sun, shade and even mites-aside – it’s entirely possible certain areas are just worse than others for planting either due to soil chemistry or even objects (rock, clay, old dead tree roots) buried under the surface. Hope things have improved for you!
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  5. Chris Castagna says:

    I read your great article and feel your pain. I have lost the same arborvitae several times – which is very is just very strange. I have a row of 5 – but only one seems to be the issue. This summer – another one has bit the dust and it kills me as this tree was about 10 feet tall and gorgeous.
    Because the same spot seems to kill my trees – I am wondering if I need to treat the soil.
    When replacing your arborvitaes – do you need to treat the soil?
    Any help would be appreciated.

    • Hi Chris – Thanks so much for your comment, and I’m glad you found the article helpful. (Kind of like a support group, right?) First, to answer your question – I have never treated my soil, no. But I’ll offer a few things that come to mind for your consideration:

      1) I’ve proactively treated these trees for mites a few times since I wrote the article (always using the Bayer Mite Control solution I mention above) – most recently ~3 weeks ago. There have been years it wasn’t necessary – but long dry periods in spring/summer trigger me as I can’ t have this happen again, and I know there’s a recurrence risk – much like it sounds like you’ve been seeing.

      2) I would surely check with a local nursery regarding your soil conditions – it’s entirely possible they may have insights here – but it may depend specifically on where you live. In my experience, I’ve always found local nursery folks to be very, very helpful with items like this.

      3) Is it possible there’s a stump of some kind buried under your tree – do you know what was there before you planted?

      4) Do you spray weed killer of any kind near the roots of the tree? If so, that’s something to be very careful-with as I believe these trees can be weakened from this; I’ve been very careful on this front myself.

      Hopefully, some of these ideas help – and if you glean any further insights, by all means – please let us know here. Because I’m positive everyone reading this article (the support group!) will be most appreciative. Best of luck to you, Chris. I really hope you can get this resolved,
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  6. Hello Mark,

    I had been in contact with you about my arbs looking ill after reading about the dreadful experience with mites on yours in this article. It’s a difficult thing trying to discover why arbs are doing great in one place and not in another. As far as my driveway ones, I suspect soil and possibly water conditions. I have sprayed them with the Bayer spray you described above and actually replaced about 4 of them already. One important thing I read was not to have rocks close at the base since the roots need air, I put some wood chips instead. Also not enough or too much water is trouble have to check on them.

    I spoke to the Agricultural Experimental Station in my state (CT) and was told it is better to get small ones and they can acclimate better since most roots are chopped so much it shocks the plants.

    I found the site below that I wanted to share with you for the website – it has loads of helpful information and is from North Dakota State University:


    Hopefully your trees are doing well.

    Regards, Nancy

    • Hi Nancy – and thank you so much for your insights and the great link above. It’s incredible how much terrific information you can find if you get to the right resource; I always gravitate toward the University and Government sources for research myself as well.

      I’m really sorry you lost 4 trees – I truly know how terribly frustrating that can be.

      One other comment relative to your point about the rocks above: I also try to be extremely careful with weed killer need the arbs for the same reason. With their surface roots, they’re quite vulnerable. And as much as I like my mulch beds to be weed free, I’m particularly careful near the Arborvitaes.
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  7. Hi, Mark–
    Thank you for such an informative article. My arborvitae is officially arbor-muerto due to mites. Is there anything special I need to know about–

    1) Disposing of the dead tree?
    2) Preparing the site for a replacement (and should I get the same kind of tree?)

    Thank you,

    • Hi Martin – For me, I soaked all of the trees with the Bayer mite killer I mentioned above. I still used gloves to handle them, though, and I definitely didn’t put them where they could touch any other living trees. Ultimately, they were mulched up. As for replacements, I had a few folks tell me replacing them was high risk – but I did anyway. (And I used the same trees.) It’s been over a year now, and everything is still nice and healthy. BUT… I’ve been very careful, doing preventative mite treatments and hose blasting as well. So far, so good. Best of luck to you, and thanks for your comment!
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  8. Hey Mark,
    Thanks for such a useful article. I never would have thought yellowing bushes could be from anything else but some weather-related issue. First ticks and now mites. Nature. And they don’t even have opposable thumbs. I can relate to planting with heavy root balls. When I first moved into my last house, I bought four of the largest hybrid maples (Autumn Blaze) that the nursery had. They came with 200 lb. root balls. Luckily my property had about a 7 degree incline. I had the foresight to dig the holes before delivery, and had them placed on delivery UP HILL from the hole. Gravity rules! On to the next article.

  9. Hello Mark, I am cringing as I read your story. I have 2 yellowing out of 15. We planted 9 last fall and the rest this spring. The 2 yellowing aren’t next to each other and were planted at different times. I will have to do the paper test and hope not to find anything but will still be out getting the “oil”. Thanks for your information, it was detailed well. I’m sorry you lost so many.

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