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Insect and Disease Guide North Shore Massachusetts

Mayer Tree Service

Essex, MA


There are many insect and disease pests of trees in Massachusetts, some more damaging than others. This picture guide is designed to help you identify what pests may be infesting your trees and shrubs, and what your options are.

There are many treatment options today, ranging from traditional foliar sprays, to soil treatments, to systemic trunk injections. Consulting a Mayer Tree Service certified arborist could put your landscape on the path to being healthy and sustainable.

In addition to managing an insect or disease issue, tree health is always another consideration. Weak and stressed trees are usually more vulnerable to attacks, so maintaining your tree’s health and vigor is sometimes the most critical, and often overlooked, treatment plan.

emlock Woolly Adelgid

Often seen as white cottony masses on the undersides of the twigs of Canadian and Carolina hemlocks, this small aphid-like pest is a serious threat to our beautiful native hemlock trees.

If left untreated, the damage begins to show as stunted, yellow growth at the tips of the branches, eventually killing off the entire branch, and spreading throughout the tree.

Several different treatment options are available, and are most effective when applied before the tree starts showing signs of decline.

Wintermoth Caterpillar

This small caterpillar is responsible for a large amount of defoliation of our deciduous shade and ornamental trees. Generally green to blackish in color, these inchworms will feed from April until June. Cankerworm, another notable caterpillar in this area, is another defoliator that looks very similar to wintermoth.

One year of leaf feeding by these pests will not likely kill a tree, but if they attack every year, then the tree becomes stressed and vulnerable to secondary pests. These insects are commonly found on fruit trees, maple, ash, oak, and some shrubs. Foliar treatments are the most effective, but systemic injections are available for trees where access is limited.


Scale insects come in many shapes and sizes, some more obvious than others. These insects are immobile, and will spend their adult life in one place. They cause damage by inserting mouthparts into the stem or leaf where they are located, and feed on the sap.

Scales can multiply rapidly, but will rarely kill its host plant. They will weaken a plant, leaving it susceptible to other insects or diseases.

Some scales will produce copious amounts of honeydew, a syrup-like substance that will coat the foliage and ground below. Black sooty mold, a fungus, will usually colonize the secreted honeydew. Seeing sooty mold is a good indicator of a scale infestation.

Treatment options will vary by scale type and host plant, but several options are available. Scales are usually found on shrubs, but some will attack trees, such as the tuliptree scale.


Lacebugs are typically found on the undersides of leaves, feeding on the sap. These insects can produce a large population, especially on plants in sunny locations. Azaleas are their preferred host, where heavy populations can remove so much sap that they turn the leaves white.

This pest is active throughout the growing season, so multiple treatments may be warranted. Soil treatments are also an option.


Sawflies are not true caterpillars, but do resemble them. They are voracious feeders, and in high numbers can devour a plant in days. European pine sawfly is commonly found on Mugo pine, but can also be found on other hard pines. Azalea sawfly is another common sawfly pest.

A foliar treatment is most effective at controlling sawflies, and timing is critical as they cause great damage in their short life span.


Leafminers are larvae that feed inside of a leaf, causing noticeable damage. Peeling open an infested leaf will reveal small, wormlike insects. They are commonly found in birch, holly, and boxwood. Extensive feeding can lead to early leaf drop, and in evergreen plants could lead to plant death.

Systemic soil treatments are generally the best option, and timing is important.


Spidermites are arachnid pests that feed on a variety of landscape plants. Some are commonly found on evergreen trees such as hemlock and fir, while other species will target deciduous trees and shrubs. They cause damage similar to lacebugs in that they remove much of the sap from the foliage, and severe infestations could seriously injure the host tree. Heavy populations will sometimes leave noticeable webbing around the foliage.

Since this pest is not an insect, special materials are needed for treatment, and foliar applications are most common.


White pine weevil is a common pest in this area, but its damage is mostly cosmetic. It will feed on white pine and spruce, causing the top terminal lead to die, which can disfigure an ornamental tree. Treatments can take care of this pest, and sometimes it can simply be pruned out.

Black vine weevil is another landscape pest, which will leave evergreen leaves notched around the edges, but can also damage the roots as a larvae. Difficult to control, this pest will require several treatments.

Carpenter Ants

While not a threat to tree health, these insects can threaten a tree’s structure. Carpenter ants will tunnel through dead wood, entering through old wounds and cracks.

The ants may not be visible at all times, but the sawdust (frass) is usually the best indicator. Since they live inside the tree, they can be difficult to control, but the use of baits and gels can be very effective at reducing their colonies.

Ticks and Mosquitoes

Ticks are not a pest of the landscape, but do pose a serious health threat to people and pets in the form of Lyme disease. Primarily carried in the deer tick, this disease can very debilitating, even fatal. People that live in areas with heavy deer populations are most prone to deer ticks. The ticks will often be found in wooded and grassy areas, and treatments are available to reduce tick populations.

Mosquitoes also pose a threat to human health in the form of Eastern Equine Encephalitis and West Nile Virus. Mosquitoes inhabit areas with stagnant water, and treatments are available to reduce their populations during the summer months.

Asian Longhorn Beetle

Although not yet a pest on the North Shore, this beetle is present in Worcester County, and was also spotted in Jamaica Plain. This destructive pest favors maple, elm, horsechestnut, birch, and others. It is a large insect, with black and white segmented antennae, that leaves large exit holes in host trees.

If you think you have seen this pest in your area, contact your arborist, tree warden, or US Forest Service immediately. Preventative treatments may be an option for uninfested trees.

Emerald Ash Borer

Not yet known to be in Massachusetts, this pest has been spotted near the border in New York. The adult insect is of little consequence, but the larvae will feed in the vascular tissue of ash trees, disrupting the trees ability to move water and nutrients.

If you see this insect, contact your arborist, tree warden, or US Forest Service as soon as possible. Preventative treatments may be available for uninfested trees.


This fungus is very common among flowering dogwoods, and several other trees. Initially it causes a dieback of new foliage, and works its way into the twig causing new twigs to die off. This can lead to a witches broom effect, a stunted appearance of the infected tree. Over time, the tree becomes weakened and vulnerable to secondary attackers such as dogwood borers.

Preventative foliar treatments, along with maintaining tree health, are the keys for managing this disease.

Similar to dogwood anthracnose, sycamore anthracnose will cause leaves to become necrotic and will often fall from the tree in midsummer. While rarely fatal for the tree, it can reduce the tree’s health and vigor, leaving it susceptible to other pests. This disease can also be found on maple, ash, and oak.

Systemic treatments are another option for this disease, and can greatly improve the appearance and longevity of the infected tree.

Apple Scab

This fungal disease is very disfiguring to the fruit and foliage of apple and crabapple trees. It can cause reduced vigor of the tree through reduced photosynthetic ability, as well as make the fruit unpalatable.
Preventative foliar treatments are an option if the conditions warrant. Apple trees require quite a commitment to keep them healthy and pest free, as well as regular pruning if fruit is desired.

Cedar-Apple Rust

This alternate host disease can distort the foliage, fruit, and twigs of apples and crabapples, but is mostly a cosmetic injury. For ornamental crabapples in areas of high visibility, it might warrant treatment.

Sometimes the more conspicuous form of this disease is the galls that form on juniper and cedar. Spores are released from here to infect the crabapple in the early spring. These galls do not need treatment, but preventative foliar treatments are available for susceptible crabapples.


Fireblight is a potentially fatal disease of ornamental trees, especially apple, crabapple, and hawthorne. This bacterial disease leaves the appearance that the foliage was scorched.

If left unchecked it will likely kill the host tree, so immediate action is suggested. Pruning out infected portions, and sometimes systemic injections, may be recommended. Tree health should also be maintained, but do not overfertilize.


Fairly common in this area, diplodia infects and kills the new growth of hard pines, including red, Austrian, and Scotch. As the disease progresses, entire branches will begin to die, leading to tree mortality.

Treatments are available, typically as systemic injections or foliar applications. Keep the tree healthy as well to improve recovery.

Cytospora Canker

This is a common fungal disease of blue spruce, as well as other evergreen tree species. Starting as a dieback of lower branches, the disease slowly progresses up the tree, causing a decrease in health and aesthetics.

Maintaining tree health is critical in trying to halt this disease, and systemic injections may also be beneficial.

Dutch Elm Disease

First seen as “flagging”, this disease quickly spreads throughout the tree, and will usually kill it within 1-2 years. American elm is the most susceptible, and few old elms exist today because of this disease.

Prevention is the key to stopping this disease, so if you have a valuable elm, a preventative treatment program would be highly recommended. It is very difficult to stop an active infection.


This root rot fungus is commonly found in evergreen shrubs, but can also infect trees such as beech and oak. A wilting of foliage is a good indicator of this pathogen.

In some situations it may be practical to apply disease treatments to the soil, and keeping the tree or shrub as healthy as possible will improve the chance of survival.

Bronze Birch Borer

White birches are highly prone to infestation of the bronze birch borer, a small woodboring insect that will kill the host tree, usually first seen as dieback from the top downward.

Visible swelling of the trunk, a “D” shape exit hole, and bronze stains are all telltale indicators. Prevention is the best recommendation, so if valuable birches are to be preserved, a systemic treatment is highly suggested.


In addition to insect and disease management, sometimes soil conditions and nutrient availability will limit a tree’s potential for growth and good health. Poor soils can be amended or even replaced to provide a better foundation for the roots to grow, and deep root feeding treatments might provide the essential nutrients the tree needs. Other applications, such as bio-stimulants and root enhancers, as well as mycorrhizae and microbes, can be added to the soil to improve root growth and soil biology.

Trees with a generally pale or yellow color, slow or stunted growth, declining branches, poor fruiting or flowering, or just a general poor appearance can sometimes be addressed by adding fertilizers and other amendments. Have a soil test taken to better address the tree’s individual needs.

Abiotic Conditions

Several other factors may lead to a tree’s decline that are not caused by an insect or disease. Poor soil, overmulching, planting too deep, improper pH, mechanical damage, grade changes, root damage, and road salts, among other things, may shorten the tree’s life or cause growing conditions that prevent the tree from thriving.

Contact Us!

Consulting a certified arborist is always a good idea when you want to protect your valuable landscape trees, and Mayer Tree Service prides itself on proper tree care and tree preservation. A consultation is always free, and might mean the difference between a healthy, structurally sound tree and a dying or hazardous tree.
We provide complete tree care programs to manage insect, disease, and nutritional needs, as well as tree pruning, tree removals, crane service, stump grinding, and more.
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