Pests of the Acadian Forest

What bugs you?

To get started on understanding  pest damage, you need to know not only about the pests themselves but also about the trees they infect.

For this reason, this presentation provides a quick review of tree species and tree parts as well as some basic information on pests.

Positive Impacts

The most important parts of the identification process are knowing what species of trees are infected and a visual inspection.

In most cases (about 70%), the insect will have left the infected trees by the time the damage is noticed and only the effects remain.  

The insect may be travelling  to other trees; however, it may be possible to prevent or slow down further damage.

Insects play necessary and beneficial roles in the forest ecology.

One of the more obvious roles is insect pollination which creates new seeds.

The forest is also renewed when insect activity kills old and weak trees allowing new growth. The dead trees are recycled by insects into soil and can be used as habitat by certain birds, reptiles, amphibians and mammals.

 Insects are also an important food source for many species of wildlife. Some insects feed on those insects that are harmful to the woodland helping to reduce the population of harmful insects.

Negative Impacts Insect activity also can have negative impacts in the

forest, especially if the damage becomes widespread.

It can reduce growth, cause deformity, and dieback, resulting in reduced tree value for the woodland owner.

Infected Christmas trees may not be sellable due to shipping restrictions.

An infected  area may look unattractive and be less appealing  for hiking or other outdoor activities. If trees in a large area die, recreational use and wildlife habitat may be reduced.

The existing tree species could be displaced and replaced by less desirable ones.

Normal versus unacceptable Some insect damage is normal in a balanced

ecosystem. A few trees damaged or killed on your woodland is probably ok, but when a population grows bigger and feeds over a greater area, the amount of damage can become unacceptable. This is often due to having a large available food

source. It can also be triggered by favourable climate

conditions. The insects and damage may affect

neighbouring  properties as well or much bigger areas. The outbreak boundaries follow the areas of food source and cross property lines.

Other causes of damage It’s not always an insect pest that is causing a tree or

stand to look “sick”. There are tree diseases that can look like insect damage.  For example,  ash trees can get a orange spot on the leaves caused by a rust disease that is similar to damage caused by an insect.

In some trees, the insect and disease work together. With Dutch Elm disease, an insect carries the fungus that later kills the tree. In beech trees, damage caused by feeding insects allows a fungus to enter later and damage or kill the  tree.  A suitable treatment may target the insect before the disease can spread.

Overly dry or wet soil can also cause trees to look damaged. After a wet season, water can pool in low areas and make Christmas trees look yellow.

In a dry season, needles can fall off and leaves can discolour. Once the tree is weakened, it may then be more susceptible to insect pests.

Identifying Pests by Host TreeIdentifying the host tree A first step to identify the pest is to

determine the tree species “hosting” the insect on your woodland.

Some insects have a preferred host species. This can be thought of as the pest’s “ favourite food”.

The pest will sometimes feed on other tree species if they are nearby or the favourite food runs out. This means  you may need to identify several host species on your woodland.

Softwood or Hardwood

A basic division for identifying trees is softwoods and hardwoods. Softwoods, also known as coniferous trees, always have needles on them. That is why they are called “evergreens”. The needles do shed - just look at the forest floor under a pine tree - but not all at once. The exception is the tamarack tree (also known as larch or hackmatack)  which turns yellow in the fall and sheds its needles.

Hardwoods, also known as deciduous trees, lose their leaves every fall after turning from green to a show of red, yellow and orange. They are usually bare in winter (a few dead leaves sometimes  hang  on) and bud out again in the spring.

Tree Species

Many woodland owners will already know the more common  kinds of softwood and hardwood trees but may not be as familiar with the various groups or species of trees, for example  red, white and black spruce.

These can be easily identified by examining the bark, needles , leaves and/or seeds. The use of Silviculture books or sheet can be used to help identify the trees.

Naming Pests Some pests are named for their appearance

such as the Whitemarked  tussock moth.

Others are named for the damage they cause such as the seedling debarking weevil. Many pests are named after a tree species that they damage such as the spruce beetle.

However in the complex world of insects, naming is far from standard. The pest and the tree species it is named after may not have a one-on-one relationship.

Some Examples:

1. Many pests will attack other species in addition to the tree species in their name. That species may be the preferred host but not the only host. An example is the balsam fir sawfly that prefers Balsam fir but also feeds on spruce.

2. For other pests, the preferred host may not be reflected in the name. The spruce budworm, for example, prefers Balsam  fir but will also feed on spruce.

3. The pest host may not apply to the Acadian Forest. The hemlock looper prefers hemlock in western Canada but likes Balsam fir in eastern Canada.

Parts of the Tree – Softwood and Hardwood

Each insect species tends to attack a specific part of a tree like the needles or the bark. Since this information is part of the identification  process, tree parts are reviewed below for both softwood and hardwood trees.

The insect world is full of exceptions and a few pests will feed on more than one part of the tree.

Note: While many pests feed only on softwood or hardwood, some feed on both.

For studying insect damage  , the tree is divided into FIVE parts:

Insect Types

The insect world is complex with over one million species of insects that change appearance as they go through their life cycle.

Fortunately, the most common insects found causing damage to your woodland can be grouped into five general types that most people can recognize in the adult stage. In general, insects do the most damage during the larval stage.

1 beetles Larval damage by beetles may include

boring under bark and into stems, and foliage feeding. Adults may cause damage to stems during egg laying (ovipositing) or while feeding on foliage, bark or stems.

2 moths Moths do all of their damage in the

larval stage by feeding directly on the foliage, mining the foliage or boring into stems. Adults for the most part do not damage vegetation.

3 flies Adult flies do very little damage  and are

responsible only for egg laying and reproduction. Fly larvae can cause a variety of damage including  gall production on stems and foliage.

4 Wasps Wasp pests include  larval defoliators,

gall makers, foliage miners and wood borers. Adult pest species may cause damage to stems and foliage during egg laying as well as some minor feeding damage.

5 True bugs, aphids or hoppers Both immature  and adult stages of these

insects cause damage. Immature stages are called nymphs – miniature  versions of the adults – and have no true larval stage. Nymphs feed in a way similar to the adult, causing damage by sucking plant juices from either foliage or stems.

6 Non insect forest Pests Insects are defined as having six legs,

three body parts, an exoskeleton (a hard shell outside the body) and most have wings.

The classification does not include spiders, ticks, mites or certain other animals similar  to insects.

Mites Mites are not insects and are more

closely related to spiders. They can however cause significant  damage  to foliage during feeding with their sucking mouthparts.

Insect descriptions include the habits and appearance  of the insect during all stages of its life cycle.

Knowing what a species looks like during each stage will help you identify the insect if it is still present.

Recognizing the insect stage is necessary for timing a treatment to prevent or limit further damage.

Four Stages in the Life Cycle

Invasive Alien Species Insects may appear on your woodland that are

not native to the area and have traveled outside their usual range. These are known as invasive alien species.

They may originate from outside Canada or from other parts of Canada.

 An insect can be alien even if it is native to Canada when it extends beyond its usual geographic range. The term alien refers to shifts across ecosystems, not simply across borders.

Insects and Climate Change

As science is showing, our climate is changing and this in turn changes  our forests.

Wetter winters, drier summers and more wind storms can stress the forest and affect which tree species grow well here. More exotic diseases and pests may be an additional stress.

As the climate changes, so do the insects living in the forest. Some may thrive and others may decline.

For example,  a DNR employee has noticed that the balsam woolly adelgid is now active in the Cape Breton Highlands where it was not found 25 years earlier. He says, “The  winters were  too cold  before and  the insects did not survive. Now in 2013, the insect  is active in all of the highlands where  balsam fir is found. It takes a sustained temperature of about -25C or lower to kill the insect  and  we rarely see those temperatures anymore.”

As new tree species begin to flourish, new insect species will grow along with them. What does this mean? We have to be aware that these shifts are occurring and learn new ways to adjust our management techniques to address them.