Bacterial Cankers And Anthracnose

Minnesota has had a wet spring. The Twin Cities have experienced a winter that seemed to drag on for longer than expected, and only reluctantly given way to a wet spring. Many people assume that an abundance of water is healthy for trees. In many cases, that assumption is true: but not always. 

Sometimes an excess of water can cause bacterial and fungal tree infections to spread more. To help homeowners ensure their trees are healthy this spring, Birch Tree Care discusses two diseases that are hampered by wet springs.

Bacterial Cankers 

The bacterium that causes canker, Pseudomonas syringae, penetrates trees through damaged bark or an existing wound, such as a pruning cut.  Bacterial canker is found commonly on Cherries, Crabapples, and Plums. Bacterial canker infections happen during Autumn, Winter and early Spring - during cool, wet weather. The infection spreads by rain, water, and pruning tools not disinfected. 

Cankers begin to form in mid-spring, and soon afterwards shoots may die back. Small holes appear on foliage from early summer.

This bacterial infection is relatively easy to spot -  "gummy" lesions characteristically form on branches or trucks. In spring, when trees begin active growth,  a sour-smelling sap may ooze from these troubled areas. The bacterial cankers become darker than the surrounding healthy bark, and the underlying tissue is moist and reddish-brown to black.

If the infected area circles the branch or trunk, the leaves above the diseased area turn yellow. When this happens, the growth of the branch or tree stops entirely, and the tree or branch dies.

Birch Tree Care has over 30+ years of professional experience in tree related diagnostics. This wealth of experience allows us to share some valuable insight with you in accurately identifying and treating a bacterial canker.

Symptoms of bacterial cancers are not only present in branches and trunks but also shoots and leaves. Other signs like wilting leaves, shoot dieback and more only make bacterial cancers easier to spot. 

Bacterial cankers may cause small brown spots to appear on leaves. These brown spots are usually round and fall out later,  leaving leaf holes. Overall, this produces an appearance that looks as if the leaves have been hit by shotgun pellets.


  1. Prune flowering trees during blooming (July and August) when wounds heal fastest.

  2. Remove wilted or dead limbs well below infected areas. Burn these branches, or take them to a landfill. 

  3. Paint the freshly cut area with wound paint to protect the tree against re-infection.

Birch Tree Care offers free quotes to customers. If you would like to have your ornamental trees expertly treated, reach out to our certified experts today.


Fungi in the genus Colletotrichum cause anthracnose. Colletotrichum is a  group of plant pathogens responsible for diseases on many plant species. Spores overwinter in infected twigs, branches or fallen leaves and spread through wind and rain the subsequent season.  

Infected plants develop dark, water-soaked lesions on stems, leaves or fruit. The centers of these lesions frequently become covered with pink, viscous masses of spores, especially during moist, warm weather. 

Common hosts include ash and oak. In ash trees, infection usually occurs in the foliage or twigs. In oak, however, the infection can happen in the twigs, shoots, leaves or buds. The optimal temperature for anthracnose to develop in ash is15-20°C and the fungus grows more rapidly with wet weather.  Oak anthracnose develops most quickly when temperatures around 10 °C.

Ash leaves infected during spring become misshapen. In early infection, leaves develop brown and yellow blotches while the edges of the foliage curl and eventually fall off.

In early infection, leaves develop blotches of necrosis, while later infections produce necrotic leaf spots with a chlorotic ring. Severe infections can cause significant defoliation: eventually, larger branches may be cankered and killed. Several seasons of infection can cause trees to decline or become susceptible to other pests. 

In oak, there are generally three phases of the disease; twig blight, where young branches are encircled and killed, shoot blight, where new shoots are killed during expansion, and leaf blight, where leaves become distorted and necrotic at the tips or along veins. Repeated infections of established trees rarely cause permanent damage, but younger trees may need protection.


  1. Remove cankered branches and prune trees. Pruning the tree increases air circulation and helps prevent moisture. 

  2. Rake and destroy fallen leaves where the fungus can overwinter. 

  3. Apply a fungicide containing Chlorothalonil.

Fungicides are toxic carcinogens and must be applied correctly. Reach out to Birch Tree Care to book tree care and expert service.

Needle Cast

Spruce (Picea spp.) is commonly planted in landscapes throughout Minnesota, and may sometimes suffer needle loss. Factors like improper planting, environmental stress, pests, and disease can all play a role in needle loss.

The two most common types of needle cast are Rhizosphaera needle cast and Stigmina needle cast.

Both the Rhizosphaera needle cast and Stigmina needle cast infect Colorado blue spruce (Picea pungens), white spruce (Picea glauca), Black Hills spruce (Picea glauca var. densata) and Norway spruce (Picea abies). While both diseases show similar symptoms, they require somewhat different management strategies.

Signs and Symptoms

A faint yellow band on needles are the first symptom to appear. The cluster gradually expands and changes from yellow to brown, or purple. Discoloured needles either fall off the tree or stay attached for a couple of years

Common signs of this disease include rows of small dark brown or black smooth round fruiting bodies (pycnidia) on infected needles. A standard magnifying glass is required to see these mature growths.  Once heavily infected needles, the pycnidia can be seen with the naked eye as continuous fine black lines up and down the length of the needle.

Rhizosphaera Needle Cast

The fungus Rhizosphaera kalkhoffii causes Rhizosphaera needle cast.

Rhizosphaera needle cast has a one-year life cycle. In Minnesota, pycnidia produce spores in late March through May, in periods of wet weather. These spores spread by rain and will infect all needles, regardless of age. The first symptoms of the disease on recently contaminated needles will appear in the spring of the following year.

Different species of spruce have different levels of resistance to Rhizosphaera needle cast.

The most susceptible spruce is the Colorado blue, the white spruce is moderately vulnerable, and the Norway spruce is resistant. For this reason, Birch Tree Care recommends planting Norway or white spruce.

Stigmina Needle Cast

The fungus stigmina lautii causes Stigmina needle cast.

Stigmina lautii has a two-year life cycle. In most cases, a year after infection the sporodochia develop just before the growth of new shoots.  In the twin cities, the stigmina lautii spores are discharged during the spring.

Susceptible varieties of spruce trees include the Colorado blue spruce and white spruce. The extent Norway and black spruce are susceptible to the fungus remains unclear. Needle loss that causes sustained growth reduction threatens the long-term health of a tree.

Preventative & Chemical Treatment

Allowing for enough spacing between trees can also help prevent the fungus spread. And, when planting new spruce trees opt for sunny locations, so needles dry quickly.

In yards, one easy way to avoid needle cast disease is to diversify the trees planted. If you want year-round green foliage, Birch Tree Care recommends planting at least two types of evergreen. Each of these different types of evergreen trees should be planted beside each other. For separate yard spruce, water them with a drip irrigation hose during a drought to reduce stress.

Fungicides can treat Rhizosphaera needle cast. For landscape trees, needles should be protected for two months after bud break. And spraying should occur every year. The timing of fungicide applications is crucial, so it’s best to hire a professional. Reach out to Birch Tree Care today.

Black Knot Fungus

The black death of trees, the black knot is as ghastly as it is apparent.

The fungus Apiosporina morbosa causes black knot. Black knot galls are most conspicuous during the fall and winter after all the leaves have fallen. So before the first buds of spring emerge, give your cherry trees a quick scan.

Even an inexperienced gardener can quickly identify black knot by its swollen, knobby black growths. These unsightly black growths emerge along the length on branches of a range of trees common in Minnesota yards. There may be many black galls on trees infected with the black knot.

The black knot fungal disease infects prunus trees, which include ornamental, edible, and native plum and cherry trees. Many Prunus trees tolerate black knot, but others are more severely affected.  In these vulnerable trees, leaves and shoots wilt and die on branches with galls.

The Lifecycle of Black Knot Fungus

During the wet periods of spring, the spores of the fungus get released. The spores are spread to other trees by the wind, where they infect young green shoots or wounded branches. The fungus grows inside the branch for many months with no visible symptoms of the disease.

As the fungus grows, it releases chemicals that make the tree grow extra plant cells that are abnormally large. In this way, the black knot is similar to cancer. This abnormal cell growth results in the swollen, woody galls on trees. What makes these galls particularly interesting are made up of both plant and fungal tissue. Black knot galls on trunks are often cracked and may ooze sticky liquid. Wood decay fungi may enter the trunk through cracks caused by black knot galls and cause wood rot.

Sometimes, the branch and the gall die after spores are released in early spring. If the branch lives, the knot keeps getting bigger and produces new spores every spring. One year after infection, galls become a swollen area of the branch with a velvety olive green covering of fungal growth. Two years after infection, the gall has turned black and hard. These galls release spores in spring when wet.  

The gall can completely encircle and girdle a branch. When this happens, the leaves beyond the gall wilt and die.

Treating Black Knot

The black knot fungus remains throughout winter in the galls on tree branches and trunks. During this time the growths are easy to spot.  Black knot is one specific tree disease that can benefit from winter pruning and spring treatment.

Winter Pruning

Pruning of infected trees should be done late winter (February or March) when the temperatures are below freezing. This important because it prevents black knot spores from infecting the pruning wound. To keep your trees free of black knot it is to inspect and prune out your trees each winter.

Infected branches need to be removed from the area and burned. It is essential that the infected pruned branches be handled correctly because the cut infected branches continue to release spores that can start new infections in the tree.

Spring Treatment

To protect young shoots from the black knot fungicides must be applied in early spring. Fungicides should be used when flower buds are just starting to open. Because fungicides are toxic chemicals,  professionals should apply them.

Reach out to Birch Tree Care today to book your spring treatment for Black Knot.

The Japanese Beetle

The Origin and Impact Of The Japanese Beetle

The Japanese beetle (Popillia japonica), originally native to Japan, has become an invasive species in the United States. Minnesota is one of the many states where the Japanese beetle is considered a firmly established pest.

Both as grubs (the larval stage) and adults, Japanese beetles are damaging plant pests.

The larvae of Japanese beetles (grubs) develop in the soil, where they feed on the roots of plants and grasses. Even in its larval stage, the Japanese beetle is capable of causing damage. As grubs, these insects destroy turfgrass in lawns, parks and golf courses.

The Japanese beetle is the most widespread turf-grass pest in the United States. Efforts to control

the insect, both in its larval and adult stages, cost more than $460 million in 2015. As the pest has spread, the costs continue to rise.  Japanese beetles can disperse by flying. Additionally, adult beetles can be moved on plant material, and larvae can be transported in the soil of nursery stock.

Adult Japanese beetles are indiscriminate about what they eat - feeding on grassroots, foliage, flowers, and fruits of more than 300 different ornamental and agricultural plants. Adult beetles feed between June and August and may cause property owners and tree care experts to worry about the pests extreme foliage consumption.

The adult beetles consume plant matter between leaf veins, giving leaves a skeletonized look. In the least impactful scenario, the Japanese beetle visibly decimates foliage, from which the plant will eventually recover. The worst case is one where the Japanese beetle causes irreparable damage to the tree.

Identifying The Japanese Beetle

The adult Japanese beetle is slightly less than half an inch long, making it about half the size of an American quarter. The males usually are somewhat smaller than the females. The beetle has a shiny, metallic-green body with bronze-colored outer wings. The beetle also has six small clusters of white hair along the sides and back of its body under the edges of its wings.

The Lifecycle and Visibility of The Japanese Beetle

Although the Japanese beetles have the lifecycle of one year, adult Japanese beetles are most likely to be seen from late spring through midsummer.

During the feeding period, June to August females periodically leave the plants they consume to burrow approximately 3 inches into the turf and lays a few eggs. This cycle of feeding and egg laying repeats until the female produces 40 to 60 eggs.

By midsummer, the eggs hatch, and the young grubs begin to feed off the roots of turf, or plants. Each grub is about an inch long (a little bigger than an American quarter) when fully grown. In late fall, the larvae burrow 4 to 8 inches into the soil where it remains inactive over the winter.  The Japanese beetle spends roughly ten months of the year within the ground in the larval stage.

In early spring, the grubs return to the turf, where they continue to feed on roots until late spring. In late spring the larvae change into pupae. Within about two weeks, the pupae become adult beetles. At this point, the mature Japanese Beetle surfaces from the ground, and the cycle repeats.

How Property Owners Can Make Informed Decisions About Treating The Japanese Beetle

While the Japanese Beetle is here to stay, there are options for managing the pest.

The first task is to survey your property for both grubs, the second is to seek professional pest treatment.

Step 1: Survey For Japanese Beetle Larve

The objective of surveying for Japanese beetle larvae is to calculate the number of beetle grubs per square foot in your lawn. This estimate is important for assessing the severity of your pest infestation, and determining whether treatment is necessary.

Japanese beetle grubs can be sampled in late summer (August to October) and late spring (April to June).

Timing will vary based on the temperature in the Twin Cities, and across the local geographic regions.

Expert Tip:  If your lawn has brown or dead areas during the normal growing season, survey near the edge of the damage. If you find that grubs are the cause of the damage, unquestionably you should book treatment.

Take several random turf samples from your lawn. Taking multiple samples is important: the distribution and density of Japanese beetle larvae grubs differ widely within a small area.  By taking several samples, you may also be able to selectively treat specific areas rather than the whole lawn. This saves you money and prevents unnecessary chemical application.

Step 2: Survey For Japanese Beetle Larve

The objective of surveying for Japanese beetle larvae is to calculate the number of beetle grubs per square foot in your lawn. This estimate is important for assessing the severity of your pest infestation, and determining whether treatment is necessary.

Japanese beetle grubs can be sampled in late summer (August to October) and late spring (April to June).

Timing will vary based on the temperature in the Twin Cities, and across the local geographic regions.

Expert Tip:  If your lawn has brown or dead areas during the normal growing season, survey near the edge of the damage. If you find that grubs are the cause of the damage, unquestionably you should book treatment.

Take several random turf samples from your lawn. Taking multiple samples is important: the distribution and density of Japanese beetle larvae grubs differ widely within a small area.  By taking several samples, you may also be able to selectively treat specific areas rather than the whole lawn. This saves you money and prevents unnecessary chemical application.

Instructions To Spot Check Larve

  1. Using a shovel, dig a square hole 8 by 8 by 3 inches deep in your lawns turf. Turn the sod over on some newspaper and search the grassroots and the soil in the hole for grubs.

  2. Record the number of grubs found in the sample location

  3. Turn the turf back into the hole and add water to help the grass recover.

  4. Collect the appropriate number of samples based on the size of your lawn (above). During each sample, collection repeat steps 1, 2 and 3.

  5. Calculate the average density of Japanese beetle larvae per square foot of your yard.
    Average pest density = (Total the number of large recorded at each sample site) / The number of samples collected.

  6. Convert these numbers to the number of grubs per square foot, multiply them by 2.25.

  7. Generally, you should consider treating areas in your lawn with more than 10 grubs per square foot.

Step 2: Hire A Professional To Treat Pest Infestation

Timing and precise application of pesticides are the two most critical factors in the chemical treatment of pests, like the Japanese beetle.

Pesticides are toxic materials: users must read and follow label directions precisely. When used improperly, insecticides can pose serious hazards to both people and wildlife. For this reason, it is best to hire a professional plant health care expert to treat pests.

Reach out to the Birch Tree Care team today for a free quote.

Apple Scab

Minnesotans who grow apples at home have to battle many insect pests and diseases to produce a good crop, even if it's just for residential consumption.

Apple scab is the most common disease of ornamental crabapples in Minnesota. The fungus (venturia inaequalis) infects not just crabapples, but also other varieties of ornamentals as well.

If the apple scab infection occurs during the early stage of fruit development, the mature fruit may become deformed and cracked as the fruit grows.

Trees infected by apple scab may have leaves with olive green or brown spots. Highly infected leaves yellow and fall off early, sometimes near mid-summer.

Numerous years of early leaf loss can result in decreased tree growth, diminished bloom and heightened susceptibility to winter tree damage.

In the long term, planting disease-resistant fruit varieties is the most effective way to manage apple scab.

For those who have existing plants that are not resistant to this type of fungus, fungicides are the best option. Proper timing and correct application are required to ensure safety and effective treatment.

To successfully manage apple scab, fungicides need to be applied before leaf spots appear.  Apple scab spores are released very early in the growing season, which means fungicide sprays must begin when the first green leaf tips emerge in spring.

Fungicides only prevent healthy trees from infection. Once apple scab spots appear on the leaves of the tree, fungicides will not control the disease. Spraying an infected tree may minimize the spread of fungus but will need to be re-treated the following year at the correct time.

Like pesticides, fungicides are toxic. Reach out to the experts at Birch Tree Care to get a free quote.

Common Tree Pests & Diseases In Minnesota

For property owners, trees and plants add beauty and value. However, when care is not taken, diseases can take root; causing decay and other health problems leading to death and destruction. Property owners should hire an I.S.A certified arborist to conduct a thorough examination of all trees and plants on their property on an annual basis.

Tree diseases can affect the health of your trees and shrubs in a variety of ways, and therefore necessitate different types of treatment. Each genus and tree species are susceptible, to varying degrees, to different insects or tree diseases. As a property owner, you want to keep your eyes open for a few common symptoms, such as leaf spots, powdery mildew appearing on the leaf surfaces and leaves turning yellow out of season.

If any of the above symptoms present themselves, it can be a sign that an insect or disease could be affecting your trees.  Property owners should take action and call a local tree and plant health care specialist, such as Birch Tree Care. Birch Tree Care knows all the pests and diseases affecting Minnesota and operates in St Paul's, Minneapolis and the surrounding metro area.

The most common insect in Minnesota is the EAB, and the most common tree disease is the Dutch Elm disease.  The fungus causing Dutch Elm Disease prevails as the most widely spread, with the spread of infection being caused by beetles and root grafting.

Dutch Elm Disease (DED)

Some tree diseases are serious and damaging in their effects. Dutch elm disease falls into this category. As professionals and experts in the field, the severity of this threat cannot be understated.

In the early 20th century, a strain of the fungus arose and the destruction of elm trees started. Data shows that almost all of the United States, and all of Minnesota, falls within the area of infection.  In the past few decades, the vast majority of mature European elms or American elms have succumbed to the Dutch Elm disease. This fungal disease has resulted in the death of millions of elm trees across the United States.

Dutch elm disease is a pervasive tree disease is caused by the fungi ophiostoma ulmi and novo ulmi. The destructive fungi infect tree roots but cause tree death by affecting the trees vascular system.

In a tree, it is the xylem and phloem tissue that deliver water and nutrients to the rest of the plant.  In simple terms, xylem and phloem make up the "transport system" for water and nutrients in a tree.

In an attempt to block the fungus from spreading farther, the tree reacts by plugging its xylem tissue with gum and tyloses. What this means is that the tree has "cut itself off" from a critical part of the transport system for nutrients and water.

By creating "plugs" to prevent the spread of the virus, the tree buys itself more time but ultimately dies.  Eventually, starvation kills the tree. Symptoms of Dutch Elm disease usually starts with the wilting, yellowing and shrivelling of the elm leaves.

Dutch Elm disease poses an invasive threat to properties because the disease spreads easily by the bark beetle, scolytus multistriatus. This particular beetle is known more commonly as the European Elm Bark beetle, Elm Bark beetle. The beetle is difficult to detect and lives within an infected host tree. Through feeding, the Elm Bark beetle transfers the fungal disease to healthy trees, compromising them as well.

The solution to Dutch Elm disease requires more than a simple pruning: it necessitates certified arborists. Certified arborists should be consulted to provide a management plan for properties with salvageable elm trees.

The most effective solution is for the entire tree to be cut down or removed. The elm wood should then be burned, chipped or buried.  The stump of the dead infected tree must be handled in one of two ways: it must be debarked or removed.

If a property owner chooses to have the infected stump debarked, it must be done to the existing grade. Debarking is necessary because it minimizes the environment suitable for bark beetle feeding and mating.

If a property owner chooses to have the infected stump removed, it should be done through professional digging and grinding. If the stump is nether debarked or removed, this can cause the disease to spread.

Other trees on the property need to be treated or removed. This is required to prevent a second wave of the disease outbreak, caused by beetle feeding or root graft infection.  Birch Tree Care can confidently advise you as to the best and most affordable way to mitigate infection.

For high-value elm trees, like large legacy trees, you should act quickly to try and preserve these trees.  It is best to treat trees preventatively before signs and symptoms present themselves. However, for those who do not treat preventatively, getting treatment at the earliest sign of symptoms is vital. Fungicides must be injected into trees infected by Dutch Elm disease, and those at risk of infection.

Fungicide injections prevent the movement of the fungi into parts of the tree (or trees) that are not yet colonized. Using fungicides to treat Dutch elm disease is important in symptomatic and non-symptomatic trees. Within the industry, several different fungicides have been used but all are relatively expensive and none are completely effective.

Birch Tree Care specialists have extensive experience with best in class certifications for fungicide application. Our professional experience means that you can be sure that your trees receive the best treatment and protection.

Emerald Ash Borer (EAB)

The Emerald Ash Borer (EAB)  is a sophisticated killer: it leaves no hint of death until later when it has moved onto its next victim. This invasive insect has infected much of North America and was confirmed in Minnesota in 2009.  This invasive species has killed tens of millions of ash trees across the United States.

The Emerald Ash borer, agrilus planipennis, is an invasive insect that destroys ash trees. Adult beetles lay eggs on the bark of ash trees, and once hatched into larvae, they move under the bark and feed on the tissues of the tree. The tissue the larvae feed on transports water and nutrients from the roots to the rest of the tree. It is the destruction of this critical tree tissue that causes the ash tree to die over time.

Examining trees for the presence of the Emerald Ash Borer is used as the most common method to detect the pest.  For homeowners and gardeners looking to identify the beetles' presence on their property, look out for the beetle's metallic green hue.

In the early stages of EAB infestation, symptoms are not readily apparent. This makes the infestation difficult to notice until dying ash trees become visible. The EAB takes between one to four years to destroy a single host tree, and each year the insect is present, it has an opportunity to repeat its lifecycle, increasing the number of pests. The EAB emerges as adult beetles in spring, leaving D-shaped exit holes in the bark of the ash tree.

While not relevant for all homeowners, the presence of woodpeckers may be a sign of Emerald Ash Borer infestation. Frequently, trees bearing a lot of woodpecker markings are infected with the EAB.

The best course of action is to remove the infected tree before the maturation and spread of the pest in spring.  Even if property owners do not detect the presence of the EAB until trees are terminal, tree removal is still required. Calling in a tree expert, such as those at Birch Tree Care, is recommended. Homeowners will need to remove the dead tree but also get help in detecting signs of infection in other trees.

When it comes to managing the spread of the EAB, homeowners, governments, and tree and plant experts all play a role.  The emerald ash borer is most commonly spread by the transportation of firewood. However, the insect can also be spread through the movement of other infested ash wood items, such as some packing material. The US Department of Agriculture strongly recommends that individuals living in infected areas not move firewood.

If you think your trees may be infected by the Emerald Ash Borer, call Birch Tree Care for a free quote.

Crabby About Crabgrass On Your Property? Let Us Help!

Crabby About Crabgrass On Your Property? Let Us Help!

It’s that time of year when the fresh green grass begins to emerge in homeowners’ yards, signifying the spring is here to stay. But grass doesn’t always make its debut alone—sometimes crabgrass threatens to steal the spotlight. After hiding in the soil all winter long, this course, yellow weed can begin to sprout and damper the look and feel of your lawn. Learn how to prevent and control this unappealing grass so your yard is looking pristine for the summer.