Got Nature? Blog

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Cold winter winds, alternating extreme temperatures, ice and snow can be damaging to trees and shrubs. However, this spring, we are seeing additional damage due to the harsh winter conditions that is of the furry kind: rabbits and rodents. Mice and rabbits often damage young trees in the winter by feeding on the juicy, green cambium layer just under the bark and girdling the tree. Damage from these furry creatures occurs most commonly in winters when there is prolonged, heavy snow cover and food is scarce. Sound familiar? Rabbits feed on the bark above the snow while mice tunnel under the snow and feed near the ground level. Mouse damage is usually more severe when the trees are surrounded by heavy grass, weed cover or heavy mulch.

On young trees and multi-stemmed ornamental trees, rabbits remove the bark completely around the trunks and stems, effectively girdling them. All growth above the girdled areas will eventually decline and die, and for most situations, replacing the girdled trees is the best course of action. There are no applications that will mitigate the effects of rabbit damage or save severely damaged trees. Wound dressings, pruning paints, latex paints, wrappings and other alleged protective barriers do not help.

Many deciduous shrubs have the ability to produce new shoots or suckers at their base. Because of this ability, many severely damaged deciduous shrubs can recover. However, patience is required as several years may be required for some shrubs to fully recover. In early spring as the greening begins, prune off girdled stems just below the damaged areas. This will help rejuvenate the plant in most circumstances and replace the damage growth.

The most effective deterrent to girdling by mice or rabbits is to wrap the trunk and low branches of young trees with screen wire or hardware cloth. Be certain the wire wrap is buried below the ground line and extends high enough above the possible snow line to prevent rabbits from reaching to the trunk or branches. To help control mouse damage, maintain an area free of grass or weeds for a 1- to 2-foot radius around the base of the tree. Additionally, maintain proper mulch levels, never more than 2-3”, to eliminate the habitat for mice. Various chemicals are available to repel mice and rabbits, but these do not afford the reliability of a well-made barrier.

Resources
Preventing Wildlife Damage, The Education Store, Purdue Extension
Vole Damage in Pumpkins (and other crops), Purdue Extension – Forestry and Natural Resources (FNR) Got Nature? Blog
Moles, The Education Store, Purdue Extension resource center
Adjuvants and the Power of the Spray Droplet: Improving the Performance of Pesticide Applications, The Education Store
Preventing Wildlife Damage – Do You Need a Permit?, The Education Store
Attract Hummingbirds to Your Yard, Video, Purdue Extension Youtube Channel
How to Stop Woodland Animals from Digging in Your Flower Pots, Video, Purdue Extension Youtube Channel

Purdue Extension – Forestry and Natural Resources

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Carpenter ants are very common inside trees, especially on larger, mature trees that are hollow with cavities. They nest in rotted, decayed wood, although some nests may extend into sound heartwood in the center of the tree. Carpenter ant presence is an indication of rotting wood, and infested trees should be checked to determine whether the rot has weakened the tree enough that it has become a risk of failure.

Carpenter ants in trees are not directly harmful to the tree. Control is not necessary for the tree’s health; their presence indicates decay in the tree, and they only feed on dead wood fiber. Wood decay can set in if moisture is present; it is the wood decay that gives the carpenter ants the opportunity to colonize the tree. Carpenter ants use knots, cracks, holes and old insect tunnels to gain access to these areas.

Control of carpenter ants inside trees is difficult but can be done as a way to reduce invasion of the ants into adjacent structures and places where they are unwelcome. It is also possible for ant colonies located inside trees to form satellite colonies inside a nearby home wall. Available controls are not likely to permanently rid a tree of carpenter ants, so retreatment every year or so may be necessary. Dust insecticides (such as Sevin or Abamectin) labeled for use on trees in the landscape are suggested for control. Apply the dust directly into the nest cavity.

Sealing tree cavities or treating tree wounds with wound dressings is not advised. Such treatments are unnecessary and will not eliminate nor prevent decay or carpenter ant activity. Also cutting down otherwise viable trees that happen to be infested with carpenter ants is generally not necessary unless the tree poses a risk.

Resources:
Household & Structural, Department of Entomology, Purdue University
Who Let the Bugs Out?, 4-H Purdue Extension – Entomology
The Space Invaders of Summer, Purdue Agriculture News
Report Invasive Species, Purdue Invasive Species
The GLEDN Phone App – Great Lakes Early Detection Network
EDDMaps – Early Detection and Distribution Mapping System (Report Invasives)
Subscribe – Purdue Extension-FNR YouTube Channel, find videos for wildlife, forestry, urban forestry, community development and more.

Lindsey Purcell, Chapter Administrator & Master Arborist
Indiana Arborist Association

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