Trim an Elm in August

Question: Hello Master Gardener:

We have an ~ 100 year old elm tree in our yard.  We treat the tree with fungicide injections every two years.  

Recently an employee of the treatment service trimmed several dead branches and suggested that the tree now has Dutch Elm disease (he removed bark from a trimmed branch and showed us brown streaking). He suggested that the best course of action is to immediately remove one of the four main branches of the tree to stop the infection.

However, the tree trimming service we use said that removing a branch this time of year (late July or August), could invite even more rapid spread of Dutch Elm.

My question:  Should we remove the main branch now (in early August), or wait until October / November when the beetle is dormant?

Thank you.

responder: Steve Miles  Master Gardener, Hennepin County MN (I answer using human intelligence, not AI)  Replied July 22, 2024, 11:55 AM EDT
response: Thank you for writing. The instructions on this are not clear. Dead branches or dying branches with intact bark or structurally unsound branches may be taken down promptly.  https://www.alberta.ca/dutch-elm-disease-prevention-what-you-can-do https://extension.umn.edu/plant-diseases/dutch-elm-disease Elm disease infected branches should be completely removed anytime if the signs of infection are is at least 5 feet from the trunk.  All such wood from trees with Dutch Elm Disease should be disposed of as if infected with the disease.  Without seeing all of the base of this tree, it appears to have three trunks at highly acute angle.  Such trees are at increased risk of catastrophic failure if disease gets to the core.  I suggest that you urgently address this matter with your arborist.

responder: The Question Asker Replied July 22, 2024, 12:28 PM EDT
response: Hi Steve:   Thank you for your response.  It helps.   You seem to be suggesting that the risk of trimming infected branches (5 feet from the last sign of streaking) in August is LOWER (in your opinion) than the risk associated with waiting until October.  Correct?   Note:  We realize that the ultimate decision is ours.   Ed Parker HyAxiom M: 612.961.5330 E: <personal data hidden>    From: ask=<personal data hidden> <ask=<personal data hidden>> On Behalf Of Ask Extension Sent: Monday, July 22, 2024 10:56 AM To: Edward Parker <<personal data hidden>> Subject: Re: Trim an Elm in August (#0148153)     ÁÖÀÇ: ÀÌ ¸ÞÀÏÀº ¿ÜºÎ¿¡¼ ¹ß¼Û µÇ¾ú½À´Ï´Ù. ¸µÅ È¤Àº Ã·ºÎÆÄÀÏ ¿¶÷ ½Ã ÁÖÀÇÇÏ½Ã±â ¹Ù¶ø´Ï´Ù.  CAUTION: This email is sent by an external account. Please take extra caution when clicking the link or opening the attachment.

responder: Steve Miles  Master Gardener, Hennepin County MN (I answer using human intelligence, not AI)  Replied July 22, 2024, 1:03 PM EDT
response: Thank you for writing back. I am conveying the finding on proper management of a governmental and university authorities.  I am a messenger in the sense that I found those relevant authorities.  In my opinion and given an incomplete photo of the base of the tree, the primary danger here may be catastrophic splitting of the three trunks of this tree.  Arborists have specialized tools for assessing this risk.  I would appreciate hearing your arborists opinion. Note: you should rely on the view of an ISA certified arborist.  https://extension.umn.edu/planting-and-growing-guides/how-hire-tree-care-professional

responder: The Question Asker Replied July 22, 2024, 4:47 PM EDT
response: Hello Steve:   Thank you for your response.  We will find an ISA-Certified arborist for another opinion and forward you the information when we have it.   Ed Parker HyAxiom M: 612.961.5330 E: <personal data hidden>    From: ask=<personal data hidden> <ask=<personal data hidden>> On Behalf Of Ask Extension Sent: Monday, July 22, 2024 12:04 PM To: Edward Parker <<personal data hidden>> Subject: Re: Trim an Elm in August (#0148153)     ÁÖÀÇ: ÀÌ ¸ÞÀÏÀº ¿ÜºÎ¿¡¼ ¹ß¼Û µÇ¾ú½À´Ï´Ù. ¸µÅ È¤Àº Ã·ºÎÆÄÀÏ ¿¶÷ ½Ã ÁÖÀÇÇÏ½Ã±â ¹Ù¶ø´Ï´Ù.  CAUTION: This email is sent by an external account. Please take extra caution when clicking the link or opening the attachment.