# Help! Something is Killing My Arborvitae Trees! **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [October 15, 2003, 5:04pm UTC](https://boards.straightdope.com/t/help-something-is-killing-my-arborvitae-trees/207605 "2003-10-15T17:04:37Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![ralph124c](https://avatars.discourse-cdn.com/v4/letter/r/8797f3/32.png) [@ralph124c](https://boards.straightdope.com/u/ralph124c)\ **Post date:** [October 15, 2003, 5:04pm UTC](https://boards.straightdope.com/t/help-something-is-killing-my-arborvitae-trees/207605/1 "2003-10-15T17:04:37Z")
I planted a row of arborvitae trees in my yard (5 years ago). They are now about 6’ hihg…but lately, the tips of the needles have been turning brown! I’m afraid some kind of disease is killing them! My brother had a similar situation with his spruce trees…a good does of BEYER insecticide fixed it…anybody know what I should do? ---
**Author:** ![tomndebb](https://avatars.discourse-cdn.com/v4/letter/t/b9e5f3/32.png) [@tomndebb](https://boards.straightdope.com/u/tomndebb)\ **Post date:** [October 15, 2003, 6:25pm UTC](https://boards.straightdope.com/t/help-something-is-killing-my-arborvitae-trees/207605/2 "2003-10-15T18:25:23Z")
If it is an insect, you should be able to see the damage. (Chewed needles/fronds, holes in the trunk bark leaking sap from borers.) If it is a fungus, it may be harder to spot. (Although powdery mildew will look like a thin white powder.) Have you had drought this summer? Leaf tips turning brown _can_ be a sign of too little water. Your best bet might be to contact your County Agricultural Agent (known in may locales as the County Extension Agent or Service). They should be able to identify the problem and also suggest a solution. ---
**Author:** ![tomndebb](https://avatars.discourse-cdn.com/v4/letter/t/b9e5f3/32.png) [@tomndebb](https://boards.straightdope.com/u/tomndebb)\ **Post date:** [October 15, 2003, 6:31pm UTC](https://boards.straightdope.com/t/help-something-is-killing-my-arborvitae-trees/207605/3 "2003-10-15T18:31:24Z")
If it is an insect, you should be able to see the damage. (Chewed needles/fronds, holes in the trunk bark leaking sap from borers.) If it is a fungus, it may be harder to spot. (Although powdery mildew will look like a thin white powder.) Have you had drought this summer? Leaf tips turning brown _can_ be a sign of too little water. Your best bet might be to contact your County Agricultural Agent (known in may locales as the County Extension Agent or Service). They should be able to identify the problem and also suggest a solution. ---
**Author:** ![tomndebb](https://avatars.discourse-cdn.com/v4/letter/t/b9e5f3/32.png) [@tomndebb](https://boards.straightdope.com/u/tomndebb)\ **Post date:** [October 15, 2003, 6:51pm UTC](https://boards.straightdope.com/t/help-something-is-killing-my-arborvitae-trees/207605/4 "2003-10-15T18:51:00Z")
[Arborvitae Diseases (Penn State)](http://www.cas.psu.edu/docs/CASDEPT/PLANT/ext/arborvit.html) [Arborvitae disease factsheets (Cornell)](http://plantclinic.cornell.edu/treeshrub/arborvitae.htm) [THUJA INSECT PROBLEMS (Michigan State U)](http://www.msue.msu.edu/msue/imp/modzz/00001446.html) [THUJA DISEASE PROBLEMS (MSU)](http://www.msue.msu.edu/msue/imp/modzz/00001447.html) [ARBORVITAE / WHITE CEDAR (Thuja occidentalis) DISEASES (U of Minnesota)](http://www.extension.umn.edu/projects/yardandgarden/diagnostics/arborvitae.html) [Eastern Arborvitae Thuja occidentalis (Purdue)](http://www.fnr.purdue.edu/extension/SpecTop/EasternArborvitae.html) (General description with problems at bottom of page) ---
**Author:** ![french\_frog](https://avatars.discourse-cdn.com/v4/letter/f/c77e96/32.png) [@french\_frog](https://boards.straightdope.com/u/french_frog)\ **Post date:** [October 15, 2003, 6:54pm UTC](https://boards.straightdope.com/t/help-something-is-killing-my-arborvitae-trees/207605/5 "2003-10-15T18:54:29Z")
Ask if you can try copper sulfate (in France they use it neutralised in neutral lime (20%copper). You usually dose 10 to 20 gr per liter of water and spray it on anything that had insects of fungus. Very efficient, used a lot on vinetrees and cypress. The only drawback is the blue color of your tree after the treatment… ---
**Author:** ![tomndebb](https://avatars.discourse-cdn.com/v4/letter/t/b9e5f3/32.png) [@tomndebb](https://boards.straightdope.com/u/tomndebb)\ **Post date:** [October 15, 2003, 6:56pm UTC](https://boards.straightdope.com/t/help-something-is-killing-my-arborvitae-trees/207605/6 "2003-10-15T18:56:17Z")
(The Purdue site reminded me that too wet conditions can be as bad as too dry, and that transplanted trees are susceptible to the wrong acidity.) ---
**Author:** ![handy](https://avatars.discourse-cdn.com/v4/letter/h/b5a626/32.png) [@handy](https://boards.straightdope.com/u/handy)\ **Post date:** [October 15, 2003, 9:48pm UTC](https://boards.straightdope.com/t/help-something-is-killing-my-arborvitae-trees/207605/7 "2003-10-15T21:48:19Z")
I’d take some samples to a nursery & ask them. If your city has a forester you could ask him, ours does & I do ask him. ---
**Author:** ![AskNott](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/asknott/32/5790_2.png) [@AskNott](https://boards.straightdope.com/u/AskNott)\ **Post date:** [October 16, 2003, 5:28am UTC](https://boards.straightdope.com/t/help-something-is-killing-my-arborvitae-trees/207605/8 "2003-10-16T05:28:09Z")
**Handy** is on a good track, but take the samples **in zip-bags!** You don’t want to risk infesting the nursery’s stock.