Category Archives: Disease – Conifer

Nectria Canker

What is Nectria canker? Nectria canker is a common and potentially lethal disease that affects many species of trees and shrubs. This disease can cause significant damage on newly planted, as well as on established, trees and shrubs that are under stress.

For more information on Nectria canker:  See UW-Extension Bulletins A3281, A1771, A1817, A1730 and A2308 or contact your county Extension agent.
For more information on Nectria canker: See UW-Extension Bulletins A3281, A1771, A1817, A1730 and A2308 or contact your county Extension agent.

What does Nectria canker look like? Nectria canker is characterized by the production of sore-like wounds (cankers) that form on twigs, branches, and trunks. Cankers can form at leaf scars and wherever injuries occur. Injuries can be caused by pruning (particularly improper pruning), frost, hail, cracking from heavy snow or ice, sunscald, insects, or mammals. Cankers appear first as slightly sunken areas on the bark, but can grow for years, becoming target-shaped or elongated. Small branches girdled by cankers can wilt suddenly, fail to leaf out, and die.

Where does Nectria canker come from? Nectria canker is caused by two fungi, Nectria cinnabarina and Nectria galligena. These fungi survive in the margins of cankers where they produce numerous fruiting bodies (reproductive structures). Fruiting bodies can be cream, coral, orange, or red, and eventually darken to brown or black with age. Spores are dispersed by wind, water, and pruning tools. Cankers grow slowly, usually when the host is dormant, or under stress. Infected plants may hold the fungus in check by producing wound-closing (callus) tissue around the infected area.

How do I save a tree with Nectria canker? There is no cure for Nectria canker. Remove smaller branch cankers by pruning six to eight inches below the canker. Disinfect pruning tools after each cut by dipping them for at least 30 seconds in a 10% bleach solution or alcohol (spray disinfectants that contain at least 70% alcohol can also be used). Trees with trunk cankers may live many years with the disease. Healthy trees are better able to slow the development of Nectria canker, so make sure that trees are watered and fertilized properly.

How do I avoid problems with Nectria canker in the future? Choose plants that are well-adapted to your local climate. Avoid any stresses to your trees and shrubs. Prune properly (see UW-Garden Facts XHT1014 and XHT1015), and avoid injury to root and trunks from lawnmowers. Remove grass from around the base of trees and shrubs, mulch properly, and water as needed to avoid drought stress.

For more information on Nectria canker: See UW-Extension Bulletins A3281, A1771, A1817, A1730 and A2308 or contact your county Extension agent.

Lichens

What are lichens? Lichens are organisms that arise from mutually beneficial interactions between certain fungi and algae. The fungi provide the physical structures of the lichens, as well as protection for the algae. The algae, in turn, produce food for the fungi via photosynthesis.

There are many types of lichens.  Crustose lichens (left) are crust-like and adhere tightly to the surface upon which they grow.  Foliose lichens (right) are leaf-like and composed of flat sheets of tissue that are not tightly bound.
There are many types of lichens. Crustose lichens (left) are crust-like and adhere tightly to the surface upon which they grow. Foliose lichens (right) are leaf-like and composed of flat sheets of tissue that are not tightly bound.

What do lichens look like? Lichens come in four basic growth forms. Crustose lichens are crust-like and adhere tightly to the surface upon which they grow. Foliose lichens are leaf-like and composed of flat sheets of tissue that are not tightly bound together. Squamulose lichens are composed of scale-like parts. Fruticose lichens are composed of free-standing branching tubes.

Where do lichens come from? Lichens are everywhere. There are an estimated 13,500 to 17,000 species of lichens, and lichens can be found growing in tropical, temperate and polar regions throughout the world. Lichens will grow on almost any surface that is stable and reasonably well-lit. In temperate regions, lichens can often be found growing on the bark of trees or old fence posts. Others lichens grow in less hospitable places, such as bare rock surfaces or old headstones in graveyards, where they aid in the breakdown of rocks and the formation of soil.

How do I save a tree with lichens? DO NOT PANIC! Lichens do not harm trees; they are not pathogens or parasites, and do not cause disease. Lichens are self-reliant, with the algal component of the lichen producing food for the organism via photosynthesis. Lichens absorb water and minerals from rainwater and the atmosphere, and because of this, they are extremely sensitive to air pollution. As a result, the presence or absence of certain lichen species can be used as an indicator of levels of atmospheric pollutants. Information on the abundance and species of lichens growing in an area can give a good indication of the local air quality.

There are many types of lichens.  Squamulose lichens are composed of scale-like parts.  Fruticose lichens are composed of free-standing branching tubes.
There are many types of lichens. Squamulose lichens are composed of scale-like parts. Fruticose lichens are composed of free-standing branching tubes.

For more information on lichens: Contact your county Extension agent.

Herbicide Damage

What is herbicide damage?  Herbicide damage is any adverse, undesired effect on a plant that is caused by exposure of that plant to a pesticide designed for weed control (i.e., a herbicide).  Any plant can be subject to this problem.
 

Squash leaf distorted due to exposure to a common lawn herbicide.
Squash leaf distorted due to exposure to a common lawn herbicide.

What does herbicide damage look like?  Symptoms of herbicide damage vary depending upon the plant affected and the herbicide used.  Common symptoms include stems that are flattened, or that twist or corkscrew.  Leaves may have abnormal shapes, sizes or textures.  In addition, leaves or leaf veins may yellow or redden.  In severe cases, plants may brown and die.  Some plants, such as tomatoes and grapes, are particularly susceptible to herbicide damage and can be used as indicators of unwanted herbicide exposure.
 
How does herbicide damage occur?  Herbicide damage results when an herbicide is misapplied.  Herbicides for control of broadleaf weeds are occasionally applied with fertilizers as part of a lawn care program.  If these products are applied too close to ornamentals or vegetables, or are applied when there is too much wind, then the herbicide can drift (move) from the area of application into an untreated area.  Often, drifting herbicides are difficult to detect by eye because they are extremely fine mists and can better be detected by smell.  Some herbicides readily produce vapors that can begin to drift several hours after application. 

How do I save a plant that has been damaged by herbicides?  Don’t panic!  There is nothing you can do after plants have been exposed.  However, most plants accidentally exposed to broadleaf herbicides applied with lawn fertilizers do not receive a high enough dose to kill them.  Young growth exposed to the herbicide will be distorted and discolored, but subsequent growth will be normal.

How do I avoid problems with herbicide damage in the future?  When using a lawn herbicide, follow the application directions exactly.  Don’t apply the product too close to, or in a manner that will cause exposure to, non-target ornamentals or vegetables.  To avoid drift, apply the herbicide when there is as little wind as possible (< 5 mph).  Apply the herbicide at low pressure to minimize production of fine mists.  Finally use amine forms rather than ester forms of herbicides as amine forms are less likely to produce vapors.

For more information on herbicide damage:  See UW-Extension Bulletin A3286 or contact your county Extension agent.

Dothistroma Needle Blight

What is Dothistroma needle blight?  Dothistroma needle blight is a common needle disease that can affect over thirty species of pine trees.  In Wisconsin, Austrian pines are most commonly and severely affected by this disease. 

Brown needle tips are a typical symptom of Dothistroma needle blight.
Brown needle tips are a typical symptom of Dothistroma needle blight.

What does Dothistroma needle blight look like?  Dothistroma needle blight first appears as dark green, water-soaked spots on the needles.  The spots become tan, yellow, or reddish-brown, and may encircle the needles to form bands.  The tip of the needle beyond the band eventually dies leaving the base of the needle alive and green.  Young trees are more likely to suffer damage than older trees.  Seedlings (< 1 yr. old) can be killed within a year after infection.

Where does Dothistroma needle blight come from?  Dothistroma needle blight is caused by the fungus Dothistroma pini which survives in diseased needles.  Watch for tiny, black reproductive structures of the fungus (called pycnidia) that can be found erupting from the surface of infected needles.  Spores are produced in these structures throughout the growing season, and infection by spores can occur at any time, but particularly during periods of wet weather.  Symptoms appear from five weeks to six months after infection. 

How do I save a tree with Dothistroma needle blight?  Copper-containing fungicides (e.g., Bordeaux mix) can help prevent new infections, but will not cure diseased needles.  Typically a single fungicide application in early June is sufficient to provide protection of new foliage.  However, a second application three to four weeks later will provide more complete control.  Be sure to read and follow all label instructions of the fungicide that you select to ensure that you use whatever fungicide you select in the safest and most effective manner possible.  Several years of treatments may be needed to completely rid a tree of all infected needles (through natural needle loss).  Trees with severe infections (> 40% of the crown affected) may not survive and should be removed. 

How do I avoid problems with Dothistroma needle blight in the future?  DO NOT plant Austrian pines as they are extremely susceptible to Dothistroma needle blight.  Use white or Black Hills spruce, or white fir instead.  If you decide to plant susceptible trees, make sure the trees are disease-free at the time of planting.  Also, be sure to provide adequate spacing between the trees to ensure good airflow and promote rapid needle drying.  If you have established trees that are suffering from Dothistroma needle blight, remove fallen needles from around the base of these trees as these can serve as a source of fungal spores.

For more information on Dothistroma needle blight:  See UW-Extension Bulletin A2620 (available at http://learningstore.uwex.edu), or contact your county Extension agent.

Diplodia Shoot Blight and Canker

What is Diplodia shoot blight and canker?  Diplodia shoot blight and canker (formerly Sphaeropsis shoot blight and canker) is one of the most common fungal diseases of Austrian pine in urban settings in Wisconsin.  This disease can also affect other pines including red, jack, Scots and mugo pine, as well as other conifers including cedars, cypresses, firs, spruces and junipers.

Diplodia Shoot Blight and Canker
Diplodia Shoot Blight and Canker

What does Diplodia shoot blight and canker look like?  Initially you may notice branch tips that ooze a large amount of resin.  Eventually, these branch tips brown and die.  Often, the newest needles on these dead branches will be of different lengths.  As the disease progresses, sunken or swollen, discolored areas (called cankers) may form on infected twigs.  Heavy resin flow and an absence of tunnels help distinguish Diplodia shoot blight and canker from damage caused by insect pests.
 
Where does Diplodia shoot blight and canker come from?  Diplodia shoot blight and canker is caused by the fungus Diplodia pinea (formerly known as Sphaeropsis sapinea).  The fungus survives in infected shoots and pinecones where it produces small, black fruiting bodies and dark-colored spores. 

How do I save a tree with Diplodia shoot blight and canker?  Immediately remove and destroy diseased branch tips.  Prune branches six to eight inches below the point where they are obviously infected.  Prune only in dry weather.  Between cuts, disinfest shears by dipping them for at least 30 seconds in a 10% bleach solution or alcohol (spray disinfectants that contain at least 70% alcohol can also be used).  This will prevent accidental movement of the fungus from branch to branch during pruning.  Also, where possible, remove and destroy pinecones from infected trees.

How do I avoid problems with Diplodia shoot blight and canker in the future?  Stressed trees are more likely to be infected by Diplodia.  Therefore, minimize any stresses to established conifers.  Water your trees adequately, particularly during dry periods.  When planting new trees, be sure to allow ample space for roots to grow, avoid compacting the soil around your tree and make sure there is adequate soil drainage.  Also fertilize your conifers properly (every three to five years), but do not overfertilize, particularly with nitrogen.  Finally, you may want to apply a fungicide containing thiophanate-methyl or chlorothalonil (or a combination of both products) at 14 day intervals between bud break and full shoot elongation to help prevent infections.  Be sure to read and follow all label instructions of the fungicide that you select to insure that you use the fungicide in the safest and most effective manner possible.

For more information on Diplodia shoot blight and canker:  See UW-Extension Bulletin A3643, or contact your county Extension agent.

Cytospora Canker

What is Cytospora canker? Cytospora canker is one of the most common fungal diseases of Colorado blue spruce. This disease can also affect Norway spruce (and less frequently other spruces) as well as Douglas-fir and balsam fir. Trees that are 15 years old or older and are at least 20 feet high most typically show symptoms of this disease.

Death of lower branches of Colorado blue spruce typical of Cytospora canker.
Death of lower branches of Colorado blue spruce typical of Cytospora canker.

What does Cytospora canker look like? Cytospora canker usually first appears on lower branches and progresses up the tree. Individual upper branches may show symptoms as well. Needles on infected branches turn purple, then brown and die. Diseased needles eventually fall off and the infected branches die. Infected branches often produce a bluish-white sap that oozes somewhere along their length.

Where does Cytospora canker come from? Cytospora canker is caused by the fungus Leucocytospora kunzei (also referred to as Leucostoma kunzei), which survives in infected branches. Spores of the fungus are spread by wind, rain splash, insects, birds and mammals.

How do I save a tree or shrub with Cytospora canker? Immediately remove and destroy any diseased branches, by pruning them using the 3-point method of pruning (see University of Wisconsin Garden Facts XHT1014 for details). Prune only in dry weather. Between cuts, be sure to clean your pruning shears by dipping them for at least 30 seconds in a 10% bleach solution or 70% alcohol (spray disinfectants that contain at least 70% alcohol can be used). This will prevent movement of the fungus from branch to branch, or from tree to tree during pruning. DO NOT attempt to use fungicide treatments to control this disease.

How do I avoid problems with Cytospora canker in the future? Perhaps the easiest way to avoid Cytospora canker is to avoid planting Colorado blue spruce. If you do plant blue spruce, allow adequate spacing between trees in new plantings. For established trees, judiciously prune branches to open the trees’ canopies. Proper spacing and pruning promote increased airflow, which leads to a less favorable environment for infection and disease development. In addition, minimize any stress to your trees. Prevent water stress by avoiding soil compaction, and by making sure there is adequate soil drainage. During dry periods, water your trees adequately (approximately one inch of water per week) using a soaker or drip hose. Proper mulching (one to two inches on a heavier, clay soil; three to four inches on a lighter, sandy soil) can help moderate your trees’ moisture levels. Prevent nutrient stress by properly fertilizing your conifers based on a soil fertility test. The University of Wisconsin Soil Testing Laboratories (http://uwlab.soils.wisc.edu/) can assist with soil and plant tissue fertility testing.

For more information on Cytospora canker: See UW-Extension Bulletin A2639 (available at http://learningstore.uwex.edu), or contact your county Extension agent.

Conifer Disease Quick Reference

Conifer - Root and Crown Rot Root and Crown Rots Hosts: All conifers Pathogens: Pythium spp., Phytophthora spp., Rhizoctonia solani, Fusarium spp., Cylindrocarpon spp. For more information see: UW Garden Facts XHT1070
Conifer Rhizosphaera Needle Rhizosphaera Needle Cast Hosts: Colorado blue spruce, other spruces, many other conifers Pathogen: Rhizosphaera kalkhoffii For more information see: UW Garden Facts XHT1006; UW-Extension Bulletin A2640
Conifer - Cytospora Canker Cytospora Canker Host: Colorado blue spruce, other spruces Pathogen: Leucocytospora kunzei For more information see: UW Garden Facts XHT1003; UW-Extension Bulletin A2639
Conifer - Spruce Needle Drop Spruce Needle Drop Hosts: Spruces Pathogen: Unknown (thought possibly to be Setomelannoma holmii)
Conifer - Cedar Apple Rust “Cedar-Apple” Rust Hosts: Junipers, apple, crabapple, hawthorn, quince Pathogen: Gymnosporangium spp. For more information see: UW Garden Facts XHT1009a/b; UW-Extension Bulletin A2598
Phomopsis Tip Blight Phomopsis Tip Blight Host: Junipers Pathogen: Phomopsis juniperovora For more information see: UW Garden Facts XHT1099
Conifer - Diplodia Tip Blight Diplodia Tip Blight Hosts: Pines (Austrian, red, jack, Scots, mugo), many other conifers Pathogen: Diplodia pinea For more information see: UW Garden Facts XHT1010; UW-Extension Bulletin A3643
Conifer - Dothistroma Needle_ Dothistroma Needle Blight Hosts: Pines (Austrian, red, Scots, mugo, ponderosa, and others) Pathogen: Dothistroma pini For more information see: UW Garden Facts XHT1078; UW-Extension Bulletin A2620
Conifer - Drought Stress Drought Stress Hosts: All conifers Cause: Insufficient water
Conifer - Winter Injury Winter Injury Hosts: All conifers, particularly yews and junipers Cause: Dehydration over the winter
Conifer - Herbicide Damage Herbicide Damage Hosts: All conifers Cause: Exposure to a growth regulator herbicide such as 2,4-D or dicamba For more information see: UW Garden Facts XHT1004; UW-Extension Bulletin A3286

For more information on conifer diseases: See University of Wisconsin Garden Facts XHT1003, XHT1004, XHT1006, XHT1009a, XHT1009b, XHT1010, XHT1070, XHT1078, XHT1099, XHT1118 or XHT1119, UW-Extension Bulletins A2598, A2620, A2639, A2640, A3286, or A3643, or contact your county Extension agent.

Chlorosis

What is chlorosis? Chlorosis is a common nutritional disorder of many woody ornamentals in Wisconsin, particularly in the southern and eastern parts of the state. Pin oaks are most commonly affected by chlorosis, although many other trees and shrubs (e.g., white oak, red maple, white pine and Rhododendron spp.) are also very susceptible.

Yellowing of foliage characteristic of chlorosis.
Yellowing of foliage characteristic of chlorosis.

What does chlorosis look like? Symptoms of chlorosis are easy to distinguish from those of other diseases. Affected leaves turn yellow, except for the veins, which remain green. In severe cases, foliage may turn brown and die. Symptoms can occur on isolated branches, or over an entire tree.

What causes chlorosis? Chlorosis occurs when a tree or shrub is lacking certain micronutrients, in many cases iron or manganese. Lack of micronutrients in a tree may reflect a lack of these nutrients in the soil due to poor fertility. Often, however, there are sufficient micronutrients in the soil, but they cannot be absorbed by a plant’s roots. Poor absorption of micronutrients is common in Wisconsin because of the high pH (alkalinity) of many soils.

How do I save a tree or shrub with chlorosis? Chlorosis is rarely fatal and can be treated. For treatments to be effective, you must determine the exact cause of the chlorosis. Have the soil around an affected plant tested for micronutrients and for pH prior to applying any treatment. If the soil test indicates a lack of specific micronutrients, fertilize with these micronutrients. For example, chelated iron compounds can be used to increase the amount of iron in soil. If the soil test indicates a high soil pH, lower the pH by applying sulfur or ammonium sulfate (see University of Wisconsin Garden Facts XHT1151). Contact your county Extension agent for information on soil testing, and for details on a treatment once you have determined the specific cause of your chlorosis problem.

How do I avoid problems with chlorosis in the future? Plant trees and shrubs that are less susceptible to chlorosis, and make sure your trees and shrubs receive sufficient water (approximately one inch per week). This will help plants with micronutrient uptake. If rainfall is insufficient, use a drip hose or soaker hose to apply supplemental water. Remove turf from around the base of a tree and shrub out to at least the drip line, and apply shredded hardwood, pine or cedar mulch in this area to help keep the plant’s root system moist. On heavy clay soils, use three inches of mulch. On other soils, use three to four inches of mulch. Be sure to keep mulch two inches from the main trunk of a tree. If you decide to plant susceptible trees or shrubs, watch them closely for yellowing characteristic of cholorosis and apply corrective treatments as soon as symptoms appear. Treatments should always be based on the results of soil micronutrient and pH tests.

For more information on chlorosis: See UW-Extension Bulletin A2638 (available at http://learningstore.uwex.edu) or contact your county Extension agent.

Armillaria Root Disease

What is Armillaria root disease? Armillaria root disease, also known as shoestring root rot, is an often lethal disease of tree and shrub roots and lower stems. It can affect almost any conifer or hardwood species, from seedling to maturity. Trees and shrubs stressed due to drought or defoliation can be particularly susceptible to Armillaria root disease.

Armillaria Root Disease
White mats of fungal tissue called mycelial fans (arrow) may be present within and beneath the bark of stems and roots affected by Armillaria root disease.

Where does Armillaria root disease come from? Armillaria root disease results from colonization of trees and shrubs by fungi in the genus Armillaria. These fungi produce tough, cord-like strands called “rhizomorphs” that grow from decaying stumps and roots through the soil. Infection of other trees or shrubs can result from penetration of intact roots by rhizomorphs. In late summer or early fall, honey-colored mushrooms of Armillaria fungi develop near the bases of colonized plants and produce spores that are distributed by wind. Infection also can occur after these spores germinate in wounds on stems or roots.

What does Armillaria root disease look like? Above-ground symptoms of Armillaria root disease may include slow growth, yellowing and dwarfing of foliage, and thin crowns. Dieback of twigs and branches also may occur as root disease progresses. These symptoms may develop slowly and intensify over many years. However, trees and shrubs also may be rapidly killed, with leaves or needles suddenly wilting or browning on a plant that appeared healthy just days or weeks earlier. Bark on lower stems or roots may be killed and crack, with flow of resin common on conifers. Thin white mats of fungus tissue called “mycelial fans” may be present within and beneath killed bark. Stem and root wood decayed by Armillaria fungi is often water-soaked, creamy to yellow in color, and spongy or stringy in texture. Rhizomorphs are commonly seen on or beneath the bark and growing from decayed stumps and roots.

Can I save a tree affected by Armillaria root disease? There is no practical way to eliminate Armillaria from trees that are already colonized by the fungus. The useful life of an affected tree might be prolonged, however, by supplemental watering during dry periods and appropriate fertilization to improve overall host condition. In very vigorous trees, the pathogen may be “walled off” and confined to just a portion of the root system or root collar. There are no chemical treatments that can effectively target the Armillaria fungi within diseased trees.

How do I avoid Armillaria root disease in the future? Practices that maintain trees in vigorous condition are the best means of preventing Armillaria root disease. Watering and fertilization to avoid stress will help trees resist infection. Because Armillaria root disease often develops in response to defoliation, suppression of both insect and leaf pathogen defoliators will indirectly reduce the occurrence and severity of Armillaria root disease. Because stumps and root systems of previously colonized trees can serve as “food bases” supporting rhizomorph growth for many years, thorough removal will reduce the risk of infection of other trees.

For more information on Armillaria root disease: Contact your county Extension agent.