Category Archives: Insects & Diseases

Planning for a Beautiful Lawn (Part 4)

Pest and disease control

The healthier your lawn is, the more likely it is to resist pests and diseases. Some pests, however, can be hard to avoid—particularly white grubs. Grubs are the larvae of beetles (primarily Japanese beetles and masked chafers) that develop in the ground. When the population of grubs is significant, you will start seeing brown patches in your lawn, particularly toward late summer. To make matters worse, grubs are a delicacy for some animals, such as skunks and raccoons. Sometimes the problem goes unnoticed until you see holes dug in your turf one morning. Grubs like sunny areas with moisture, and are not often found in shade or in dry lawns.

If you see brown patches in your turf, you can lift up a piece of turf where the brown patch meets green lawn and look at the roots to check. The grubs are white and C-shaped. It only takes about 10 grubs per square foot of lawn to cause visible damage.

If you catch the problem early, or if you see a large adult population of beetles,  Almstead lawn technicians usually perform a summer lawn treatment.  Although mid-summer and fall treatments are sometimes effective, June is the best time to prevent grubs from damaging your lawn.

There is also an effective organic treatment for grubs which we use, which utilizes milky spore, a grub-killing bacterial powder. However, this only works on Japanese Beetle grubs and must build up in your soil over time to work. We can test your lawn to identify what type of grub is living there.

Other insects, such as chinchbugs, can be damaging to lawns. When you see yellowing patches, or grass blades that have been notched and nibbled, we try to identify the insect responsible and narrowly target it with the appropriate control.

Lawn diseases are usually fungal. Fortunately, they are not common. Unfortunately, they can be difficult to diagnose and can spread quickly. If you suspect your lawn is suffering from disease rather than insect damage, it’s wise to have a sample taken and analyzed in order to determine the right treatment.

The best prevention for lawn disease and pests is maintaining the health of the lawn. A well-nourished, watered, well-mown lawn becomes a self-sustaining system that is hostile to predators.

Protecting Elm Trees Against Dutch Elm Disease (DED)

Elm trees were once the pride of New York cities and towns, with their over-100 feet heights, wide trunks and overarching spreads. Since the 1950s, however, millions of Elm trees have succumbed to Dutch Elm Disease, a fungal infection that originated in Asia but was first described in Holland in 1921 (hence the name). It began appearing in elms in the United States in the 1930s.

The disease is carried from tree to tree either by bark beetles or directly through the merged roots of two or more adjacent trees. Once a tree if infected it has no chance for survival. As a tree fights the infection, because of internal scarring, it loses the ability to transport nutrients and water through its trunks and slowly dies in a few months.

Although there is not much that can be done once an elm tree is infected, there are preventative measures that can be taken to protect these magnificent trees.

Quick Removal of Diseased Trees and Branches

It is important to remove infected trees as quickly as possible to reduce the breeding sites for the elm bark beetle and contain its spread. If the wood from infected trees is being stored for firewood, the bark must be removed from the pieces and destroyed. Branches with flagging symptoms should be removed with the cut made 5-10 feet behind any visual symptoms. Speak to your Almstead arborist about removing trees and branches that have possibly been infected with DED.

Inoculating Elm trees against DED

ten six

We have found that inoculating Elm trees as the best way of preventing Dutch elm disease. Over the past few years, Almstead has employed this method to successfully treat and prevent infection in hundreds of elm trees in our area.

We select multiple injection points in the root system of a tree and circulate a fungicide mixture simultaneously to all entry points using a pump. The concentration of the mixture is calculated based on the circumference of the trunk as well as the height and spread of the tree.

The tree does the rest. It takes in the control solution to all its branches. Depending on the size of the Elm, this can take over 5 hours. The treatment is 99.5% effective and will last for 2-3 years depending on the size and condition of the tree, at which point it will have to be repeated.

one two

For more information on Dutch Elm Disease and other pathogens that commonly affect plant life in our region, we recommend visiting

Are Emerald Ash Borers Expanding Their Diet?

Are Emerald Ash Borers Expanding Their Diet?

The recent announcement that the Emerald Ash Borer has arrived in Peekskill NY brings new urgency our local fight against this invasive insect. We strongly urge anyone who is the custodian of a healthy ash tree to consult with your arborist about the options for preserving the tree BEFORE the insect arrives in your area.

Ash Tree
The stately ash tree is one of our dominant forest trees, as well as a popular specimen tree used extensively in urban planting.

Since arriving in Michigan in 2002, the Emerald Ash Borer (Agrilus planipennis)
has cut a devastating swath through the Central and Eastern United States, killing tens of millions of ash trees — destroying over 99% of the ash population in many areas. There are currently over 8 billion ash trees in the U.S. The loss of these trees represents an environmental disaster and an economic one as well: the impact is estimated to reach $10 billion in the next 5 years.

Until recently, Emerald Ash Borer (EAB) damage had been confined to the ash species (Fraxinus). Now, researchers from Wright State University in Ohio have found evidence of EAB infestation in white fringetrees (Chionanthus virginicus), a species closely related to ash trees.

The white fringetree is a native understory tree found throughout the Eastern U.S. Although fringetrees are not important to the lumber industry, the trees fill an environmental niche in forests and are also popular as ornamental trees. In addition to the specter of another species-wide devastation, the appearance of EAB in white fringetrees causes concern because it may presage the migration of EAB to other tree species. Ash trees and white fringetrees are both members of the broader olive genus which includes common shrubs such as lilacs and forsythia.

White Fringetree
The white fringetree is named for the delicate flowers that cover it in spring.

How EAB Destroy Trees

EAB can fly about ½ mile in search of an ash tree to host their eggs. Unlike most species of boring insects that prefer to lay their eggs in already damaged trees, EAB will choose healthy as well as stressed specimens. They lay their eggs on the trunk and leave them to dine on the ash. As the larvae develop, they bore into the ash tree, carving serpentine galleries as they gnaw into the tender cambium just beneath the bark. Once infested, ash trees typically die within 2 to 3 years, as the damaged cambium becomes incapable of supplying water and nutrients to the branches.

Although EAB will relentlessly expand their territory every year, they have often had help in increasing their range. People unwittingly moving firewood have transported EAB to new locations, causing the epidemic to move even faster.

Emerald Ash Borer Larva
The serpentine galleries carved in the cambium nourish the larvae but kill the tree.

What Can We Do?

At this point, EAB has no natural predator in this country – unlike in Asia where it originated. Scientists are studying several species of wasp that prey on EAB in its native range for possible control, but no solution seems imminent.

Meanwhile, we have the ability to save individual ash trees. Keeping ash trees healthy will boost their immune systems and help them resist any opportunistic pests. Systemic injections will stop EAB larvae from damaging a valued ash tree. Depending upon the treatment chosen and the timing, a single treatment can provide control and protection for 2 to 3 years.

Investing in preserving specimen ash trees has multiple benefits. In addition to maintaining and enjoying an individual iconic American tree, every ash tree that survives the onslaught of EAB will act as a genetic reservoir for repopulating this beautiful species after the EAB is – hopefully – controlled or eradicated.


Seeing Inside a Tree

As an arborist, my preference is caring for trees rather than removing them.  However, sometimes there is no choice, particularly when a broken or diseased tree is in danger of harming people or property. Unfortunately, most of these trees do become removals.

Many trees live long lives with imperfect health. They experience damage from insects or disease, but manage to compartmentalize it and continue to grow and even thrive. Often we are able to help these trees with improved nutrition, better soil, and insect or disease control; their lifespans can improve by decades due to some extra care.

Recently, one of our clients asked us to evaluate an old walnut tree. The 150-200 year old tree is on a beautiful estate in Larchmont, accompanied by some of the original larches that gave the town its name. The property has a long history of homeowners who care deeply about the trees, and the current owner obviously continues this tradition.

It was clear that the tree had some substantial decay, but the homeowner was hoping that the damage wasn’t extensive enough to warrant removal yet. So the question was: how do we determine whether this magnificent tree had reached the point where it was too dangerous to remain? This was the time to employ one of the tools of our trade, a sophisticated piece of equipment called a Resistograph.

The Resistograph allows us to chart the density of a tree, millimeter by millimeter. A tiny drill bit goes into the wood of a tree and transmits a graph indicating the resistance the drill bit encounters. This gives us a map of the tree core. We use this data along with other information to calculate the level of risk associated with the tree’s potential failure.

chema in a tree

Trees are amazing structures that can continue to stay alive and grow with much of their heartwood rotted away. Because trees have their water and nutrition transport system close to the bark, the inner part of the tree serves little purpose – except to provide the core strength that keeps several tons of branches and leaves upright. Unfortunately, we had to tell this client that the walnut tree had lost so much of its core that it was no longer safe.

As you can see from the picture, the Resistograph told the truth: this tree was essentially EMPTY.  The 4’ diameter hole could easily accommodate our crew member. If you suspect one of your trees may be hollow or simply want to perform Risk Assessments for trees which you may be concerned about, Almstead arborists have the training and tools needed to gather that information so homeowners can  make a properly educated decision.

–  Jeff Delaune, Arborist

Unwanted Pest #1: Bronze Birch Borer

We have gotten to the end of our list of the Most Unwanted Insects. For #1 we chose the Bronze Birch Borer (Agrilus anxius).

unwanted birch borer

Why did we choose the Birch Borer for the #1 spot rather than the insects that can destroy an entire tree species? (i.e. the Emerald Ash Borer or the Asian Longhorned Beetle)  Because it’s HERE. NOW.  And because, as arborists, we’re dealing with damage – often fatal — from this insect all the time.

We all love birch trees. The bright, white, striped paper bark birch is often the first tree we recognize as children. As an understory tree, white birch can light up the forest. Seeing a birch grove in the snow is breathtaking. And other birches, such as river birch with its curling peek-a-boo bark revealing a salmon-colored trunk, are popular planting choices as well.

The problem with birch is that they are really not meant for our landscapes.  Under the best circumstances, birch trees don’t have lives as long as most of our other trees. And our yards and parks are not the best of circumstances. Birch trees grow best in slightly acidic, moist, well-drained soil.  They like sun on their faces but not on their feet. They don’t like pollution. When they don’t have the right conditions, they become stressed; this makes them more vulnerable to both insects and disease. The attacks of insects like the birch leafminer and aphids or diseases like rust and mildew further compromise the tree’s health.

This is where the Bronze Birch Borer comes in. The Birch Borer lays its eggs beneath the bark of the birch tree – and prefers to have its path cleared by another insect or other damaging agent  first. So Birch Borers rarely attack healthy trees, but can be deadly to trees already experiencing some decline.

As the Birch Borer larvae emerge they ravenously eat the underside of the bark, gouging out galleries as they munch. These channels cut through the phloem of the tree, interrupting the tree’s ability to transmit water and nutrients.

Larva and gallery of the Bronze Birch Borer Source: David G. Nielsen, The Ohio State University,
Larva and gallery of the Bronze Birch Borer
Source: David G. Nielsen, The Ohio State University,

Because the larvae grow beneath the tree bark, often the infestation goes unnoticed until the tree canopy starts to yellow, at which time it can be too late to save the tree.  It takes aggressive treatment to halt an attack of Bronze Birch Borers. In an infested tree, the trunk can be injected with a control that can help to stop the larvae from developing. The trunk can also be sprayed with a substance that helps to prevent new insects from colonizing the tree. The correct treatment depends upon the health of the tree, the degree of infestation and the time of year.

Not all birch species are equally vulnerable to Bronze Birch Borer. The River Birch, in particular, seems to resist the insect, while the Silver Birch is particularly susceptible. Ultimately, the best way to prevent the Bronze Birch Borer from killing your trees is to keep your Birches as healthy as possible.  Birches need deep watering  — weekly, at least.  Although the leaves need sun, the roots must stay cool, so a layer of ground cover or mulch will help to insulate them from the heat.

We recommend checking Birch trees frequently for signs of pests and disease. Any yellowing leaves or dieback could indicate a potentially fatal problem; early intervention can sometimes avert a fatal infestation.

Unwanted Pest #2: Asian Longhorned Beetle

We’re almost to the end of our series on the Most Unwanted Garden Pests. This is villain #2: The Asian Longhorned Beetle (ALB). 

unwanted alb

The ALB (Anoplophora glabripennis) doesn’t live in our area (Westchester, Bergen and Fairfield counties) – yet. And hopefully, it won’t. Intensive eradication efforts are ongoing in New  York City, Long Island, Massachusetts, Union and Middlesex counties in New Jersey and Ohio, the areas where ALB is currently residing. The USDA is taking an aggressive approach to this mission – any tree infested by ALB is cut down and burned.

Why is the ALB so despised? Because of the deadly outcome of an ALB infestation and the extensiveness of their diet.  In our area, we’ve had several species of trees virtually eradicated by insects or disease over the last century: the American Chestnut by chestnut blight, the American Elm from Dutch elm disease, and – currently – several species of ash trees from the Emerald Ash Borer. But the Asian Longhorned Beetle has the potential to decimate several widely growing tree genera in our area, including maple, birch and sycamore. In addition to the loss of these beautiful trees, the economic impact on our hardwood forests would be immense.

The story of the ALB’s infiltration into the U.S. sounds like a spy movie. Someone notices a suspicious looking insect. They call a government agency. The insect is identified as a stowaway assassin from China. Soon after, the Feds swoop in and destroy the insects along with any possible hiding place. They search the neighborhood looking for more insects and any possible shelters – and in a slash and burn frenzy, cut down any trees that could harbor these terrorists.

Yet this dramatic response seems to be yielding results. The ALB appears to have been eliminated in the Chicago area, and it looks like New York and New Jersey may soon follow. Massachusetts is still battling hard and finding new ALB hideouts.

The USDA’s Animal and Plant Health Inspection Service (APHIS) actually acts like Homeland Security for invasive pests. They have intercepted ALB in warehouses in California, Florida, Illinois, Indiana, Massachusetts, Michigan, North Carolina, New Jersey, New York, Ohio, Pennsylvania, South Carolina, Texas, Washington and Wisconsin.  And their Canadian counterparts have intercepted the ALB in several provinces there.

Asian Longhorned Beetle Exit Holes Source: Kenneth R. Law, USDA APHIS PPQ,
Asian Longhorned Beetle Exit Holes
Source: Kenneth R. Law, USDA APHIS PPQ,

One thing that works against the ALB is its size and striking markings. The beetles are over an inch long and colored like a Mardi Gras mask. In several cases, an ALB was identified when someone saw it and said, “What IS that thing?”  When a tree is infested with ALB, the exit holes can make it look like it’s been strafed with a machine gun.

Right now, the best chance we have of defeating the ALB is public awareness. So if you see a large, gaudy beetle, call for backup! This USDA site will give you more information: (It’s worth visiting just to see their CGI beetle!)

Unwanted Pest #3: Hemlock Wooly Adelgid

If you have hemlocks in your yard, you probably already know of the Hemlock Woody Adelgid (HWA). This tiny aphid-like insect has been attacking and killing hemlocks throughout the eastern United States.  The devastation it causes makes it #3 in our countdown of Most Unwanted Landscape Pests. unwanted adelgid Both the Carolina Hemlock and the Eastern Hemlock are victimized by the Hemlock Wooly Adelgid. This insect doesn’t restrict itself to weak or stressed trees – healthy trees can be infested as well. Although a tree can survive an attack from the HWA, continued infestation is deadly, robbing the tree of the needles necessary for survival. There are no preventive measures for HWA; hemlocks should be inspected frequently for signs of infestation. You aren’t likely to see the adelgids:  they are so tiny they are almost imperceptible. But the signs of their presence are unmistakable: little dots of cotton appear along the base of the needles where they meet the wood. These cottony blobs are protecting the HWA eggs. When the crawlers emerge, they will latch on at the base of a needle and start draining the hemlock of its vital fluids. Obviously, a single adelgid doesn’t drink much; but as the population grows, the cottony balls extend along every branch, harboring millions of thirsty adelgids. Within a few years of infestation, the hemlock is usually dead. Some of our beautiful, native hemlock forests have disappeared because of this foreign invader.

Hemlock with wooly adelgids. Source: John A. Weidhass, Virginia Polytechnic Institute  and State University,
Hemlock with wooly adelgids.
Source: John A. Weidhass, Virginia Polytechnic Institute and State University,

Fortunately, this is an insect that we can successfully battle. Both foliar sprays and systemic controls are available that can give us the upper hand against these insects. There are several factors that should be considered in order to determine the best course of treatment, such as the size of the tree, the extent of infestation, soil and weather conditions and proximity to streams or ponds. Your Almstead arborist will evaluate how these factors impact your hemlock and propose a method for combating these evil adelgids. In the future, there may be biological controls for HWA. Currently, experiments with predatory insects and fungi look promising, especially for forests where the cost of treating individual trees is impractical. For now, careful monitoring and early action are the best safeguards against Hemlock Woody Adelgid.

Unwanted Pest #4: Scale

Our reverse countdown continues. #4 in our list of the most Unwanted Landscape Pests is Scale. 

unwanted scale

Scales are tiny insects, less than ¼”, that do almost nothing – except suck the life out of plants. There are 7,000 different types of scale insects, broadly divided into armored and soft.

Scales live boring lives. A female insect attaches herself to a leaf or shoot and begins to feed. She lays eggs beneath herself (some scale insects mate while others can reproduce without outside help) and provides shelter while they develop. “Crawlers” emerge and start to seek out their own locations. After a few days their mobility is over: they hook onto a plant and begin sucking — forever.

Woolly Pine Scale Source:  Terry S. Price, Georgia Forestry Commission,
Woolly Pine Scale
Source: Terry S. Price, Georgia Forestry

Although immobile, scales have protection. Armored scales create a hard protective covering, basically a shell. In fact, some scales are referred to as oyster shell, while others look like small pearls. Soft scales are covered in a waxy coating; they often appear as fuzzy white dots of fluff on a plant. Most release fluids as they suck; this sticky “honeydew” can cause even more problems by attracting other insects or mold – and dripping on anything below.

Scales are so tiny that they are rarely noticed until the population has increased to troublesome size. But, en masse, they can harm or even kill plants – even trees. Their lack of mobility causes them to feed in ever-increasing numbers on their host plant.

Scale’s armored or waxy coating makes them difficult to kill. They are only vulnerable to insecticide sprays during their brief crawling stage. Thorough drenching in horticultural oil or insecticidal soap can also combat scale. Finally, systemic treatments are available that cause the tree to repel the feeding insects.

Magnolia Scale Source:  Brian Kunkel, University of Delaware,
Magnolia Scale
Source: Brian Kunkel, University of Delaware,

There is no single treatment for scale insects – nor do all scale insects need to be removed. Almstead arborists and technicians examine every tree to determine the most appropriate treatment, based on factors including the type of scale, the stage of development, and the size of the tree. 

Most Unwanted Pest #5: Elm Bark Beetles

Our reverse countdown of the 10 Most Unwanted Pests continues with #5: the Elm Bark Beetle.

elm bark beetle

Elm Bark Beetles are mass murderers, responsible for the devastation of the American Elm population – up to 99% of elms have succumbed in some areas. Once the go-to urban tree, the rows of stately elms that lined our streets and shaded our parks have disappeared due to the Dutch Elm Disease transmitted by these beetles.

European Elm Bark Beetles (Scolytus multistriatus) and the Native Elm Bark Beetle (Hylurgopinus  rufipes) make their home – and their meals – beneath the bark of trees. The beetles penetrate the bark and bore through to the sapwood. Once inside, they gouge out galleries for their eggs. The larvae develop beneath the bark of the tree and expand the galleries to eat the underside of the bark.

The hungry Elm Bark Beetle larvae gouge out these galleries as they feed. Image: Joseph O'Brien, USDA Forest Service,
The hungry Elm Bark Beetle larvae gouge out these galleries as they feed.
Image: Joseph O’Brien, USDA Forest Service,

Unlike most bark beetles that target soft-wood trees, the Elm Bark Beetle targets the hard-wood American Elm. The beetles typically lay their eggs in elm trees that are already weakened or beginning to decay. This means that Elm Bark Beetles would never have made our Unwanted list on their own: their larvae rarely do substantial damage to a healthy tree, and controls are available to fight these infestations. It is the adult Elm Bark Beetle that is causing so much such fatal damage. Although most of their lives are spent in weak trees, they fly to feed on healthy trees as part of their life cycle. They carry the fungus that transmits Dutch Elm Disease from the failing tree to its healthy neighbor.

Once the fungus enters the elm tree it starts to clog up the tree’s xylem – the aquaduct system inside the tree. The tree responds by trying to seal off the infected xylem tubes with its own clogging mechanism: this is why one of the first signs of Dutch Elm Disease is a yellowing patch of canopy as a branch stops providing water to it.

Elm tree branches affected by Dutch Elm Disease. Source:  USDA Forest Service - Northeastern Area Archive, USDA Forest Service,
Elm tree branches affected by Dutch Elm Disease.
Source: USDA Forest Service – Northeastern Area Archive,USDA Forest Service,

Can Dutch Elm Disease be stopped? Not currently. But individual trees can be maintained in good health for a long time – and a fortunate few never succumb. The first step in prevention is keeping elm trees healthy. Beetles are most attracted to trees that are already stressed, so a regular program of watering and fertilization is important.  Dutch Elm Disease also spreads less quickly in a well-watered tree – greater hydrostatic pressure can help slow it down.

There are also inoculations that can slow the progress of Dutch Elm Disease. The earlier the better.  So it’s extremely important to monitor elm trees for any signs of infestation or canopy yellowing. In the early stages, pruning can remove infected branches before the disease spreads to the rest of the tree.

Finally, if you have an elm tree that is beyond saving, it should be removed immediately. The wood must be disposed of appropriately and the stump removed. The roots should also be severed if other elms are near, to prevent the disease spreading through root connections.

Unwanted Pest #6: The Evil Weevil

Number 6 in our countdown of America’s Most Unwanted garden pests is the Black Vine Weevil.

unwanted black vine weevil

The Black Vine Weevil (Otiorhynchus sulcatus ) is a root feeder. Although adults will damage foliage, the most serious damage is done by larvae feeding on roots. The insects’ diet includes hundreds of shrubs and ornamentals, including yew, hemlock, some rhododendrons and other broad-leaf evergreens like azalea, mountain laurel and euonymus. Adults can also feed on deciduous and herbaceous plants.

When shrubs fail to put out new foliage in the spring or new foliage quickly yellows or dies, one of the first suspects is this evil weevil. Another indication is the characteristic crescent notches on the leaf margins made by adults feeding. The adults are active at night throughout the summer. The non-flying insects are about  ½” long, slate grey to blackish-brown with pitted wings and a short snout.

Prevention and Control

One important step to prevention is carefully examining new plants before bringing them home. Since adult insects are unlikely to be seen, the leaves should be checked for signs of damage.

If you begin to see leaf damage on your shrubs – or stunted growth – call your Almstead arborist for an inspection. Often, by the time the damage is noticed, the plant’s health has been seriously compromised.

Biological controls for Black Vine Weevil are beginning to be available. Nematodes (little organisms that make weevils look big) are ingested by the weevils; they then execute an Alien-worthy switch and kill their hosts. Although this biological control is promising, chemical controls are presently the usual choice for dealing with these pervasive pests. Treatments are most effective on adult populations before they begin to lay eggs. That puts the timing of treatments around late May, with repeat applications through the summer if necessary. (These weevils can have several generations per summer.)

If you didn’t treat for Black Vine Weevil this year and are wishing that you had, consider a fall treatment to reach overwintering larvae, which are found in the soil.

Unwanted Pest #7: Aphids

#7 in our series on America’s Most Unwanted garden pests is the all-too-common aphid. Aphids otherwise known as plant lice, are tiny soft-bodied, sucking insects. With over 4,400 types of aphid worldwide, they are the most common garden pest. Most aphids only target one kind of plant, while others have a much broader diet.

unwanted aphid

These tiny (1/32”) pear-shaped insects can be winged or wingless and almost any color. A colony of aphids can cause substantial damage to plants, trees and shrubs including yellowing or curling leaves and stunted growth. In addition to sucking the juices from plants, their saliva is actually toxic to many plants. Aphids often transmit fungi and disease to the plants they infest. 

Aphids with their ant bodyguards Source: E. Bradford Walker, Vermont Dept. of Forests,  Parks and Recreation;
Aphids with their ant bodyguards
Source: E. Bradford Walker, Vermont Dept. of Forests, Parks and Recreation;

In the process of feeding, aphids secrete a sticky, sugary liquid called honeydew — which can rain down from the trees on anything below it, like your car or lawn furniture. Given the size of an aphid, when there’s enough honeydew to drip from a tree, you know that there is a huge population feeding above.

The sweet honeydew is attractive to ants. Many sugar-eating ants actually act as body guards to aphids: they protect them in order to milk the aphids for honeydew. In addition to the damage aphids cause directly, the honeydew can make plants more susceptible to fungi, like sooty mold.

Potato Aphids Source: David Cappaert, Michigan State
Potato Aphids
Source: David Cappaert, Michigan State

Inspecting plants for aphids is the first step towards controlling this pest. Many aphids are well camouflaged to blend with the plants they target. Their coloring – along with their tiny size – means aphids are often overlooked until they are so numerous that they coat the plant. Aphids are a preferred food of beneficial insects like ladybugs, predatory wasps and lacewings; a sufficient population of these species can keep aphids under control.

If aphids have populated a plant or shrub, a stream of water from a garden hose can sometimes dislodge them; although flying aphids are likely to return, crawling ones often won’t make it back to the plant.

Because of the potential damage from aphids, as well as the diseases they transmit, it is wise to begin controlling aphids at the first sign of infestation. Almstead arborists offer both organic and traditional methods for control. Often a single application in spring is sufficient to keep aphids in check.

Most Unwanted Pest #8: Tent Caterpillars

Our countdown of the Most Unwanted arbor pests continues with #8: the Eastern Tent Caterpillar (and a similarly domiciled pest, the Fall Webworm).

unwanted tent caterpiller

Although many insects can be difficult to identify – or even detect – the tent caterpillar is not. One day you look at your tree and notice that something has actually pitched a tent there. The tent looks like an industrial version of a spider web: thick, white and slightly opaque. If you look carefully, you may see the newly emerged caterpillars celebrating their good fortune.

A single tent is not an infestation – yet. But often, if you continue your examination of the tree, you’ll find that it’s turned into a caterpillar campground. An infestation of tent caterpillars can defoliate – or eventually kill  –  a tree.

These insects are native to our (NY/NJ/CT) region. The larvae emerge in spring and construct a tent for their dormitory. They emerge daily to feed on the leaves of their host tree. Their favorites are black cherry, choke cherry, scrub apple and many species of ornamentals in the family Rosaceae (including serviceberry, hawthorn and many more).

A tree with several colonies of eastern tent caterpillars can be completely defoliated by the hungry grazers. Most trees can withstand this for a single season, but a repeated assault can leave the tree without the resources to survive.

For a residential tree, the unattractive appearance of caterpillar tents and the resulting defoliation are reason enough to try to remove the pests. For a smaller tree, Almstead arborists can selectively clip off the egg masses in the fall, or remove the caterpillar tents in spring. For a large tree, it is more practical to apply a control to prevent the larvae from emerging.

Just as tents in your tree in spring usually indicate tent caterpillars, similar tents in the fall are usually a sign of Fall Webworms.  Black cherry is their preferred tree but they are also common on alder, apple, beech, birch and oak.

Fall Webworm Damage Courtesy of  Ronald F. Billings, Texas Forest Service,
Fall Webworm Damage
Courtesy of Ronald F. Billings, Texas Forest Service,

In June and July, moths lay their larvae on the underside of leaves and cover them with scales. As the larvae grow, they eat the leaf tops; the tents are expanded as they move to new branches. It’s possible for the tent to envelop an entire tree and for the webworms to defoliate it completely.

The webworms don’t typically kill trees, since trees have already stored up most of their nutrients by the time the defoliation occurs. However, the effect can be grotesque. Your Almstead arborist can discuss alternatives for shutting down the tent city in your tree.

Unwanted Pest #9: Japanese Beetle

This is the second villain in our countdown of the Top 10 landscape pests in our area:


Japanese beetle

Beautifully glowing with green and blue iridescence and coppery wings, the Japanese Beetle doesn’t look like it should be despised.  But Japanese Beetles have earned their unsavory reputations by having populations that quickly grow out of control and damage almost every part of our landscape.

And summer is Japanese Beetle time: this is when the adults emerge from the ground and start dining on our plantings. With a diet that includes over 300 different plants, our yards are their buffet. They devour the soft leaf tissue of our plantings, often leaving only the leaf ribs behind. Since July is also their time to mate, a few Japanese Beetles can turn into a mob when they release pheromones that attract other beetles from a mile away or more.

In late July through August, the females lay their eggs in our lawns. It takes less than two weeks for the larvae to develop into grubs and start gnawing their way through the grass roots. These grubs are the single most damaging lawn pest we have.

There are a few different ways to control Japanese Beetles. Certainly the simplest is to remove them by hand — and if the beetles have confined themselves to a single rosebush, it’s possible to curtail their population this way. However, if they’re munching through your Birch tree – or you have no interest in hand-picking beetles – you probably should consider a more sophisticated solution. We usually recommend applying a low-toxicity spray to the most susceptible plantings, repeated 2 or 3 times over the course of the summer.

The grubs represent a different challenge. Because Japanese Beetles are very mobile, it’s possible to have lots of grubs beneath your lawn, eating the grass roots and creating dead brown patches, without seeing many adults. We have several options for treating grubs. When we confirm grub activity (we do this by lifting the soil and looking), we can apply a grub treatment. One annual application usually controls all kinds of grubs, including Japanese Beetles.

There is also a purely organic approach that targets only Japanese Beetles.  Milky disease is caused by a bacterium that infects Japanese Beetle grubs. We can apply Milky Spore powder to a lawn to control the Japanese Beetle grub population.  The Milky Spore continues to infect the beetles for several years.

One warning: many sources sell pheromone traps for Japanese Beetles. These traps work well – at attracting Japanese Beetles to your yard from all around the neighborhood. So don’t buy these traps – unless they’re a gift for your neighbor!


Unwanted Landscape Pest #10: Birch Leafminer

Today we’re starting a series on America’s Most Unwanted — or really the NY/NJ/CT region’s Most Unwanted — Landscape Pests. So we’ve selected Almstead’s top 10 unloved insects that plague our landscapes. Some of them are killers (of trees or shrubs), while others just turn a beautiful planting into a shredded mess.



The countdown begins with the Birch Leafminer. This is an insect with narrow dietary preferences: Birch trees, particularly Paper Birch, Grey Birch and European White Birch. The Birch Leafminer is a European import; unfortunately its natural predators didn’t come across the sea with it. In some areas of the U.S., the European wasps are being released to help keep the Birch Leafminer population under control.

In its adult form, the Birch Leafminer is a sawfly — but it is the larvae that really wreak havoc on the Birch leaves. These hungry little Leafminers actually insinuate themselves between the top and bottom of leaves where they munch their way along a serpentine path. As these paths intersect, large portions of the leaves start to turn brown.

Birch Leafminer Damage Source: Whitney Cranshaw, Colorado State University,
Birch Leafminer Damage
Source: Whitney Cranshaw, Colorado State University,

You’ll typically notice Leafminer activity in the tops of Birch trees — since the Leafminer mothers choose the tenderest new leaves as the best place for their larvae to survive. Whole sections can turn brown due to Leafminer activity. Though the brown leaves are unsightly, and won’t regrow during the same season, Birch Leafminers are not generally tree killers. However, if an infestation repeats itself over several years, the cumulative damage can be too much for the tree to survive.

By the time you are aware of Leafminer activity, it is usually too late to alleviate the damage for the season. As part of an Integrated Pest Management approach, our Almstead arborists  recommend early application of controls to prevent the larvae from emerging in the next season.

Integrated Pest Management Explained

We sometimes take it for granted that everyone understands what Integrated Pest Management means. It is one of the cornerstones of our tree, plant and lawn health care programs. But, since many of our clients have questions about the practice, let me give you a little more information.

Decades ago, when synthetic pesticides were developed, they were used liberally. And they were effective at killing pests – but they killed many beneficial insects as well. This means that the natural balance in the area where they were used was severely disrupted. The whole food chain was interrupted, and often the birds disappeared along with the bugs.

The concept of Integrated Pest Management (IPM) arose from a desire to work within the natural order. So, rather than saying “We’re just going to eliminate all aphids”,  we ask the question, “Are these aphids being controlled by their natural predators, like lady bugs and praying mantises?”  Or “Are there certain plants that need to be protected, because they are particularly vulnerable to aphids?” If the aphids are growing out of harmony with their natural predators – perhaps on an especially alluring rosebush — we step in with a very targeted treatment to manage their population, either by killing the adults, or more likely, preventing the larvae from emerging. So rather than indiscriminately spraying insecticide all around a garden, we will apply horticultural oil (to prevent the emergence of larvae) to the aphid-loving rosebush.

Integrated Pest Management isn’t always organic – but increasingly, we find that natural or bio-rational products are best for these narrow-focused targets.  And we’re always exploring organic options wherever possible.

So how do we know what to use and when? One of the fundamentals of Integrated Pest Management is inspection.  Our technicians go out and inspect our clients’ properties several times a year, and then use products that specifically respond to any observed insect or fungal threats.

An Almstead arborist shows a client how we inspect plants
An Almstead arborist shows a client how we inspect plants

And managing insects through applications is just one tool for keeping plantings healthy and beautiful. We can also limit the spread of insects or diseases through selective pruning of infested branches as well as by improving the overall health of plants (and their resistance to pests) by improving the soil.

Ken Almstead – CEO, Arborist

Tree Neural Networks — Think Avatar ….

If you saw the movie Avatar (and apparently, most of us did), you saw how the planet Pandora was composed of a gigantic neural network. Life, health, knowledge, strength — everything could flow through these connections from one tree to another, and to the other living creatures that could tie into the network.

This shows root graft between two Oaks. Oak Wilt is easily transmitted this way.
This shows root graft between two Oaks. Oak Wilt is
easily transmitted this way.

So often, science fiction is based in reality. Trees unquestionably maintain a network beneath the ground. As an arborist, you ignore that network at your peril — because diseases can be transmitted from one tree to another through root grafts. Trees of the same species are often able to connect their roots and establish a back and forth flow of nutrients and fluid — and some potentially deadly stuff as well. Which is why, when we consider how likely a diseased tree is to infect others, we need to think of the connections below the soil as well as well as more obvious methods of transmission (like insects). Dutch Elm Disease is a prime example. If there are nearby trees of  the same species, we try to sever those root connections by removing the diseased tree, roots and all. Then we inoculate the remaining trees and hope we got there in time.

There is more and more evidence that these neural networks allow trees to work cooperatively. If a tree is stronger and better situated — perhaps where water is more available — it can actually send fluids over to its thirstier cousin. And the same seems true for nutrients and beneficial fungi. “A little more phosphorus over here, please.”

Here’s a link to an interesting video made by Professor Suzanne Simard of the University of British Columbia. She suggests that these underground connections are sophisticated enough to be actually called communication.

– Michael Almstead, VP and arborist

Don’t Squash That Worm – He Works for Me

Every gardener knows the benefits of earthworms: they are little humus-creating machines that recycle organic material as they travel, aerating and enriching the soil as they go. Worm castings (excrement) –  and eventually the worms themselves  – decay and release nutrients back into the soil. Grass, plants and trees all benefit from the activity of worms.

It’s tempting to try and improve your soil by adding more worms — and there are plenty of places willing to sell them to you for this purpose. But soil that is inhospitable to your own worms is not going to be any more attractive to imported worms – and you wind up with some really expensive dead worm fertilizer.


There are ways to make the soil more worm-friendly, and that can start a cycle of soil improvement. Aerating compacted soil can help to make a better environment for both your worms and your plants. In addition to core aerating lawns, our Almstead arborists also use compressed air (with a tool called an Air Spade) to loosen soil around tree roots or heavily compacted places. Tree and plant roots are able to receive more water through the aerated soil – and moist soil is also worm heaven. The other thing that worms (and plants) need is nutrition. That is one reason that we enrich soil with compost and leave a thick layer of mulch on top: the worms will eat the organic material and then recycle it through the soil.

Healthy soil is not just filled with earthworms – it also contains beneficial bacteria and fungi. All these organisms, along with the roots of trees and plantings, interact to perpetuate a cycle of healthy soil creation. Here at Almstead, we like to help this process with applications of Compost Tea — a carefully-balanced, liquid compost. We brew our Compost Tea from top quality leaf and twig compost and add organic nutrients like worm castings. We nourish the beneficial microorganisms with humates and fish oil to create a nutrient-rich liquid that helps to jump-start tree, lawn, plant (and earthworm) health.

Ken Almstead, Almstead arborist and CEO

Invasive Pest Alert: Emerald Ash Borer

The Emerald Ash Borer was recently identified in West Point, NY, making the threat to our Ashes in the NY metro area even more immanent. The insect was first found in Detroit in 2002 and has killed tens of millions of Ashes as it has moved east.

This is the damage that Emerald Ash Borer larvae cause just beneath the bark.
This is the damage that Emerald Ash Borer larvae cause just beneath the bark.

The Threat to Trees

Although they’re easiest to identify as adults, Emerald Ash Borers cause the most damage as larvae. They live beneath the bark, eating away at the living cambium layer of the trunk and leaving “galleries” of removed tissue behind (see photo). It only takes 3 years for a healthy tree to die completely from an Emerald Ash Borer infestation. Signs of decline include splits in the bark, capital “D”-shaped exit holes from where the borers exit the trunk, higher than usual woodpecker activity, dropping leaves throughout the growing season, and sparseness in the canopy.

The Emerald Ash Borer is iridescent green and  smaller than a penny.
The Emerald Ash Borer is iridescent green and smaller than a penny.

What You Can Do

The key to successfully saving a tree from Emerald Ash Borer is through preventative treatment. The best treatment currently available is an insecticide injection made directly into the trunk that provides protection from EAB for 2 years. If you have feature Ash trees on your property, this is definitely a course of action to consider.

Images: Galleries – Daniel Herms, Ohio State University, Borer – Howard Russell, Michigan State University,

Water Molds Impacting Trees, Shrubs & Lawns

We’ve already mentioned in a previous post that this year has been particularly rainy (twice as wet as last year, in fact). In addition to producing a spike in insect activity, the weather has also been ideal for a set of diseases known as water molds (a type of fungi) that impact both woody plants and grasses.

Water molds spread via “swimming” spores that move easily through water. That means frequent rain and the resulting saturated soils both improve conditions for the pathogens. The movement of water above ground helps to spread the molds to new plants, and perpetually wet or damp soils allow them to thrive.


Phytopthora spp. is a set of water molds responsible for several very serious tree diseases, including Sudden Oak Death and Beech Bleeding Canker. It also affects Maples and other hardwood trees and shrubs, primarily in their root systems. Due to the especially wet weather this year, we’ve seen a lot of Phytopthora root rot in the landscape. In most cases, symptoms of decline above ground (small leaves, stunted growth, dead twigs) are traced back to the root system (where there is often discoloration, noticeable rotting, and sometimes lesions on thicker roots and even at the base of the stem).

To preserve an infected plant, treatment for Phytopthora is critical. In addition to applying controls for the disease, making environmental changes that improve drainage and keep the root system of a plant from being saturated with water is incredibly important. (In fact, sprinkler systems can be just as damaging as heavy rains in this respect — just one example of why it’s important to take all of the factors in a plant’s environment into consideration.)


Another water mold, Pythium spp. causes a number of diseases in turf-grass, including Pythium blight and Pythium root rot. Both of these diseases spread quickly and create irregular patches of brown grass on a lawn. With the blight, grass will often be wet or greasy first, turning later to a more dried out brown. You may also see fungal threads growing above ground on turn infected with Pythium blight. The root rot, on the other hand, is less obvious above ground, presenting as dead brown patches. The roots, however, are obviously rotten and discolored.

Ryegrass is especially prone to Pythium problems, as are bluegrasses and fescues. As with the Phytopthora, controls are available, but fixing drainage and irrigation problems is just as, if not more, important. Certain practices, like refraining from mowing grass when it’s wet, will also help prevent the spread of these diseases.

– Ken Almstead, Arborist in Riverdale & Lower Westchester NY

Rainy Weather Means More Insects

Have you been caught in a downpour or two this year? It might not surprise you to hear that we’ve had twice as much rain this growing season than we did in 2010. Here’s a snippet from Cornell Cooperative Extension’s July 2011 Newsletter for Professional Horticulturalists in the Hudson Valley:

According to the NOAA, March – May was the wettest 3 month period on record for New York State since weather recording commenced, 117 years ago! Here in Westchester County, we officially started taking 2011 seasonal records on March 15, and since that time, we have accumulated 20.90” of precipitation – with 5.95” of this precipitation having fallen in the month of June alone. When we compare these numbers with 2010, we note that we have accumulated over 2x the amount of precipitation (both for the month of June and the season) than we had received this time last year.

So, what does that mean for conditions in the landscape? A number of things, but let’s stick with a major one for the purposes of this post.

Scale insect infestation on a Maple
Scale insect infestation on a Maple

More Insects

Mosquitoes may come to your mind first, but the wet, warm weather has also been ideal for a range of insects that impact all sorts of plants, including trees and shrubs. Scale insects have been especially prevelant this year, with heavy infestations showing up on Maples, Dogwoods, Rhododendrons, Azaleas, Taxus (Yews), Cherries and Plums. Another prevalent pest this year is the Lace Bug, which gnaws on the leaves of both Azaleas and Andromedas. The Hemlock Wooly Adelgid has been especially active this year as well.

Lace Bug damage to Azalea leaves
Lace Bug damage to Azalea leaves

Fortunately, while some are quite serious, all of the insect populations mentioned here can be managed with proper programs. However, it is definitely important to take action, and the sooner the problem is dealt with, the better. Why? The smaller the population, the easier the problem is to control. Plus, prolonged exposure to insect damage tends to negatively impact the strength of a plant in future growing seasons even if the problem has been corrected.

Untreated Hemlock Wooly Adelgid infestations can be fatal to trees in just a few years
Untreated Hemlock Wooly Adelgid infestations can be fatal to trees in just a few years

– Jeff Delaune, Almstead Arborist in Larchmont, Mamaroneck & Rye

Image Credits: Lace Bug by Whitney Cranshaw, Colorado State University,; Hemlock Wooly Adelgid by Robert L. Anderson, USDA Forest Service,; Scale by Ronald S. Kelley, Vermont Department of Forests, Parks and Recreation,

Is My Japanese Maple Tree Dead?

“Is my Japanese Maple dead?” has been the question of the week from my clients. I’ve gotten at least 4 calls about Japanese Maples that either didn’t produce leaves at all this season or only have partially developed canopies. And I got a few calls about this last week as well

Unfortunately, the trees I’ve seen are definitely dead. Those with at least partial canopies can be helped in some cases, but those without any leaves are not going to come back.

Buds formed during the Fall, but never broke this Spring. This is a common problem with Japanese Maples this year.
Buds formed during the Fall, but never broke this Spring. This is a common problem with Japanese Maples this year.

What happened?These Japanese Maples all have buds that formed last fall, but they failed to break in the spring. All of the ones I’ve seen that failed were already withstanding less than`ideal environmental conditions. For instance, soil is raised higher than it should be around the base of trees; girdling roots are strangling the root collar; limbs are suffering from improper pruning wounds; or the trees are facing new exposure to sun due to the removal of larger trees that were providing shade to these thin barked trees.

In Pelham, a client has two Japanese Maples of similar age and size situated on her front lawn.  The one to the far right (no more than 25ft away)  is still alive and this one is stone dead.
In Pelham, a client has two Japanese Maples ofsimilar age and size situated on her front lawn. The one to the far right (no more than 25ft away) is still alive and this one is stone dead.

That explains which trees were most susceptible to failure, but the real cause of their immediate or partial death was due to extreme fluctuations in temperature. This species in particular is prone to desiccation and leaf loss when this happens with the weather. Last year was a record hot summer followed by one of the coldest winters we have seen in some time. When tree failure occurs suddenly without signs of decline in previous seasons, it is typically due to environmental stresses (as opposed to insect or disease problems, which tend to take longer to cause this serious of a decline).

–Ken Almstead, Arborist in Riverdale and Westchester NY

London Plane and Sycamore Anthracnose

With the cool, wet weather we’ve been having this Spring, tree diseases have been showing up more than usual this year. Pathogens like Anthracnose fungus thrive in this type of weather and tend to peter out when it gets warmer and drier, so their window to cause damage is a lot longer than usual.


For instance, Anthracnose might usually harm only a small portion of this London Plane tree, but this year it is almost entirely leafless, with small, stunted growth where there are leaves. You can also see witch’s brooming, where the tree is pushing out new twigs around spots that were killed by the fungus.


Trees can come back from these diseases, although they may need extra care and/or fungicide treatments. Everything should really be in full leaf by now, so if it looks like your tree is getting a slow start, it may be because of a disease like this.

– Ken Almstead, Arborist in Westchester and Riverdale

Dutch Elm Disease

Elms are beautiful and majestic trees that are certainly worth the disease prevention measures available against the devastation of Dutch Elm Disease (DED). Quick to wipe out Elms, DED is caused by a fungus that leaks toxins into the xylem (water-carrying vessels) of trees. Ultimately, water flow is so impeded that the trees wilt and die.

This Elm in Pelham, NY is exhibiting beginning signs of Dutch Elm Disease.

DED is spread not only by the elm bark beetle, but also from tree to tree through grafted root systems. So if you have elms next to each other and the disease has infected one, it may make sense to sever any grafted roots. Unfortunately, once the disease travels to the root system of a tree, its chances of survival are almost nil. If, however, the initial infection takes place in the crown, then treatment with a control and sanitation pruning to remove infested areas can be a viable treatment option.

Leaves become chlorotic/exhibit yellowing as the disease begins to plug up vessels.
Leaves become chlorotic/exhibit yellowing as the disease begins to plug up vessels.
Here’s the base of the infected 60 inch elm, the fence to the right is 6-ft. high for scale.

Although we have disease resistant elms available to us now (Princeton, Liberty, Valley Forge, Olmstead are the most common available in the nursery trade), it will take a lifetime for these trees to reach the size and form of some mature elms. Dutch Elm Disease is very heavy this year and we have been injecting larger groves of elms through Central Park. We will also be beginning to treat elms throughout Riverside Park this week and for many residential and commercial clients.

Dutch Elm
Once the elms die they quickly become brittle and hazardous and begin dropping branches.

Injection treatments are made by drilling at the base of the tree and pumping a control through the vascular system. Depending upon size and weather, one treatment can take up to 6 or 8 hours. Treatments are repeated once every 3 years, and the drilling site is small and heals relatively easily. I cannot stress enough that investment in this type of preventative treatment program is well worth avoiding the deterioration and removal of a beautiful tree.

Dutch Elm Disease injection process.
Small size of the drilling performed and left after injection process; tree easily heals this over and it is typically not noticeable 3 years later when a repeat treatment is performed.

— Ken Almstead

Hen of the Woods

I was at a client’s property the other day and ran across the unique looking Grifola frondosa fungus – commonly called Hen of the Woods (check out the similarity).

Farmyard chickens free to roam about. Scotland.

Hen of the Woods often attaches to the roots of Oaks, which was exactly the case with the specimens I saw. Unfortunately, this cool looking fungus is a parasite that extracts nutrients from a tree’s root system and tends to cause root and butt rot (decaying the tree from the bottom and rising as time progresses). In the urban forest, this can quickly lead to a hazardous tree situation. Fungi are often indicators of poor tree health, so if you see one, it’s wise not to ignore it.


-Ken Almstead