Tree Pests


Native& Non-native invasive pests effect tree health, we are particularly concerned with non-native pests such as ‘Emerald Ash Borer’ (EAB), ‘Asian Longhorn Beetle’ (ALB), ‘Hemlock Wooley Adelgid’ (HWA) that currently pose a threat to Maine’s trees. HWA is active in Southern Maine and in Portland. Please read on on for information and Maine Department of Forestry web links on each tree pests that is presently active in Portland.

Browntail Moth 

This often cyclical pest is now active in many areas in Portland, currently the epicenter is in Deering Oaks Park with minor populations in Payson Park, Franklin Street, Eastern Promenade and perhaps other residential areas.  Browntail Moth have distinctive two red dots on the abdomen, the tiny hairs can cause irritating rash and respiratory response – See web link below and, don’t touch ! Control by clipping webs prior to leaf out in mid-May.  Report sightings to Portland Forestry at  

  • Browntail Webs are typically located at the end of branches vs other tent caterpillars. 
  • BTM favorite host plants – Oak species, ornamental trees crabapples, amelanchier, hawthorn.

For more information:

Other similar pests:

*Picture below of Brown Tail Moth webs in the winter.



Winter Moth 

As of 2022, this pest has been limited in this area to Peaks Island, Little Diamond Island, nearby in South Portland and Cape Elizabeth along with reports from mid-coast Maine.  See web link info.  Control partners at the Maine Forest Service using biocontrol agent Cyzenis albicans, a tachinid fly. The winter moth invaded New England in the 1990s and is moved mostly by overwintering in the soil of landscape plant material and by flight, banding is sometime used as a local homeowner control.

More information on Winter Moth

Emerald Ash Borer (EAB) 

We have been monitoring EAB for many years and watching the progression from the mid-West and Canada to New England.  This pest in time will affect all native Ash trees, Green Ash and White Ash are most prevalent in Southern Maine.  The City of Portland has been working closely with the Maine Forest Service on surveying for this pest and found it first in Payson Park.  Portland has roughly 600 Ash trees along city streets & parks and many more woodland or forest trees mostly in riparian zones along the Presumpscot River.  The Maine State record Green Ash tree is in Deering Oaks, specimen White Ash can be found in Mayor Baxter Woods and several on Little Diamond Island and other Casco Bay island neighborhoods.

More information on Emerald Ash Borer


Map of Ash Trees in Portland Maine

Hemlock Wooly Adelaide (HWA) 

Hemlock Wooly Adelaide is a serious threat to both Canadian and Carolina Hemlock trees in Southern Maine.  Control is recommended when present.  First noticed on Great Diamond Island, we have seen this pest and treated both with bio control and chemical bark treatments in Mayor Baxter Woods and Evergreen Cemetery.  Noticed in 2021 in Portland’s West End and woodland areas.

More information on Hemlock Wooly Adelaide

Tar Spot on Maples 

This seasonal ‘nuisance’ pest is found mostly mid to late summer on Norway Maple and occasionally on other native Maple to as lessor degree.  

More information on Tar Spots on Maples


This disease issue can affect a variety of trees from Sycamore in moist spring weather to maples in mid-Summer.

More information on Anthracnose

Fact Sheet on Anthracnose

Dutch Elm Disease (DED) 

This disease is spread by elm bark beetles is a serious threat to all Elm trees including new supposed ‘disease resistant’ Elms.  Look for yellow ‘flagging’ or wilting at the end of branches in late June or early July.  This can appear to be drought stress.  The City of Portland maintains over 100 American Elm trees many of them heritage tree size.  Our larger specimen Elm trees are on a preventative DED control program and are numbered in our Elm tree inventory.  

More information on Dutch Elm Disease

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    212 Canco Road, Ste A

    Portland, Maine 


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    Alex Marshall                


    Jeff Tarling


    Timothy Stephenson

    Office: 207-808-5454

    Ranger Cell: 207-232-3721



    (207) 874-8575

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