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Various varieties of evergreens browning #871524

Asked June 04, 2024, 12:44 PM EDT

We have various pines that were fine last fall and early this spring but now have the following issues. #1 - Dwarf Mugo all the needles, except candles, disappeared. Maybe eaten (plenty of deer, but never been a problem in 7 years). Candles are growing well. 60% shade #2 - large Arbor Vitae (?) started browning about 4 weeks ago, 2 trees affected, planted in 2021, morning sun #3 - small AVitae have very severe browning and dropping. planted last year 90% shade . All trees get fertilizer tree spike in early summer and late fall. Spikes are divided into the two treatments (not being over fertilized). Not fertilized this year. All trees are drip irrigated. What could be causing this? What action should be taken?

Ramsey County Minnesota

Expert Response

Hi,
 I haven’t had a response nor can I see the progress (link),  Please update.
Thank you,
V. Kesler



On Tuesday, June 4, 2024, 11:44 AM, Ask Extension <<personal data hidden>> wrote:


Dear Vance,

Thank you for using Ask Extension. A request for support has been created and a representative will follow-up with you as soon as possible. Questions are usually answered within two business days. You can view this question's progress online.

YOUR QUESTION #0141443:

Various varieties of evergreens browning

We have various pines that were fine last fall and early this spring but now have the following issues. #1 - Dwarf Mugo all the needles, except candles, disappeared. Maybe eaten (plenty of deer, but never been a problem in 7 years). Candles are growing well. 60% shade #2 - large Arbor Vitae (?) started browning about 4 weeks ago, 2 trees affected, planted in 2021, morning sun #3 - small AVitae have very severe browning and dropping. planted last year 90% shade . All trees get fertilizer tree spike in early summer and late fall. Spikes are divided into the two treatments (not being over fertilized). Not fertilized this year. All trees are drip irrigated. What could be causing this? What action should be taken?

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The Question Asker Replied June 07, 2024, 9:21 PM EDT
We cant' determine what's causing the arborvitae to decline by viewing the photos.  There are many possibilities.  

Transplant shock might account for brown foliage on the ones most recently planted.  The shock might be exacerbated by winter burn and too much or too little water.  Other possibilities are mentioned here:

https://www.extension.purdue.edu/extmedia/id/id-477-w.pdf

https://apps.extension.umn.edu/garden/diagnose/plant/evergreen/arborvitae/foliageturnsbrown.html

The needles missing on the mugo pine were probably consumed by sawfly larvae.  This is often an annual occurrence in  mid- to late May in the Twin Cities area. Proactive checks for the presence of this pest will reduce or eliminate sawfly damage next year.  Go here to learn about pine sawflies and how to deal with them.

https://extension.umn.edu/yard-and-garden-insects/sawflies#european-pine-sawfly--1025760

An Ask Extension Expert Replied June 11, 2024, 4:32 PM EDT
Thank you for the reply.
We do have very heavy clay soil, with exception where mugos are planted.  We came back from a week long vacation and saw the needles gone and a single worm that looked very similar to the sawfly larvae.  The candles have grown very well since.

 I will double check that the larger trees are not getting too much water. As far as the smaller evergreens , they are planted in very heavy clay which we tried to amend with compost and sand but probably not even close to enough.

 We will see how the small ones do this season , but most likely be replaced with a deciduous shrub.

 For the evergreens with browning, I am assuming we should prune all that off, correct?

 We will see how the small one do, but most likely be replaced with a deciduous shrub

Thank you!
Vance Kesler


iPhone originated

On Jun 11, 2024, at 3:32 PM, Ask Extension <<personal data hidden>> wrote:


The Question Asker Replied June 13, 2024, 7:11 AM EDT
Yes, trim out any dead foliage on the arborvitaes to improve their appearance.  That works until the browning gets too extensive.

Replacement with another kind of tree/shrub is sometimes best.

Beware of the sawfly larvae.  They often seem to appear overnight and do a lot of damage in a short time. Loss of the old needles affects the mugo's appearance and can threaten its health if it occurs for several consecutive years.
An Ask Extension Expert Replied June 13, 2024, 12:34 PM EDT

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