All posts by hudelson

Early Blight

July 23, 2015 hudelson

UW Plant Disease Facts

Authors: Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 02/29/2024

D-number: D0046

What is early blight?

Early blight is one of two common fungal diseases that can devastate tomatoes in both commercial settings and home gardens. Early blight can also be a serious disease on other popular vegetables including eggplants, peppers, and potatoes. The second common tomato blight, Septoria leaf spot, is detailed in UW Plant Disease Facts D100, Septoria Leaf Spot.

Early blight of tomato. Note spots with concentric rings (arrow) and yellow haloes.

What does early blight look like?

Symptoms of early blight first appear at the base of affected plants, where roughly circular, brown spots appear on leaves and stems. As these spots enlarge, concentric rings appear giving the areas a target-like appearance. Often spots have a yellow halo. Eventually multiple spots on a single leaf will merge, leading to extensive destruction of leaf tissue. Early blight can lead to total defoliation of lower leaves and even the death of an infected plant.

Where does early blight come from?

Early blight is caused by the fungus Alternaria solani, which survives on infected plants or in plant debris. Early blight symptoms typically begin as plant canopies start to close. Denser foliage leads to high humidity and longer periods of leaf wetness that favor the disease.

How do I save a plant with early blight?

Once symptoms of early blight appear, control is difficult. Thinning of whole plants or removal of selected branches from individual plants may slow the disease by increasing airflow and thus reducing humidity and the length of time that leaves remain wet. Fungicides labeled for use on vegetables and containing copper or chlorothalonil may also provide control of early blight if they are carefully applied very early in the course of the disease (before symptoms develop is best) and on a regular basis throughout the rest of the growing season. If you decide to use fungicides for disease control, be sure to read and follow all label instructions of the fungicide that you select to ensure that you use the product in the safest and most effective manner possible.

How do I avoid problems with early blight in the future?

Destroy infected plants and plant debris by burning (where allowed by local ordinance) or burying them. Move vegetables to different parts of your garden each year to avoid areas where the early blight fungus may be present. See University of Wisconsin Garden Facts XHT1210, Using Crop Rotation in the Home Vegetable Garden, for details on this technique. Use early blight-resistant vegetable varieties whenever possible. Increase spacing between plants to increase airflow, and decrease humidity and foliage drying time. Mulch your garden with approximately one inch of a high quality mulch, but DO NOT overmulch as this can lead to wet soils that can contribute to increased humidity. Finally, where the disease has been a chronic problem, use of preventative applications of a copper or chlorothalonil-containing fungicide labeled for use on vegetables may be warranted.

For more information on early blight:

Contact the University of Wisconsin Plant Disease Diagnostics Clinic (PDDC) at (608) 262-2863 or pddc@wisc.edu.

This Fact Sheet is also available in PDF format:

Full Color PDF

An EEO/Affirmative Action employer, University of Wisconsin-Madison Division of Extension provides equal opportunities in employment and programming, including Title IX and ADA requirements. This document can be provided in an alternative format by calling Brian Hudelson at (608) 262-2863 (711 for Wisconsin Relay).

References to pesticide products in this publication are for your convenience and are not an endorsement or criticism of one product over similar products. You are responsible for using pesticides according to the manufacturer’s current label directions. Follow directions exactly to protect the environment and people from pesticide exposure. Failure to do so violates the law.

Thanks to Karen Delahaut, Lisa Johnson and Ann Joy for reviewing this document.

A complete inventory of UW Plant Disease Facts is available at the University of Wisconsin-Madison Plant Disease Diagnostics Clinic website: https://pddc.qa.webhosting.cals.wisc.edu.

Submit additional lawn, landscape, and gardening questions at https://hort.extension.wisc.edu/ask-a-gardening-question/.

Disease - Broad Leafed Woody Ornamental

Dutch Elm Disease

July 23, 2015 hudelson

UW Plant Disease Facts

Authors: Jim Olis* and Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 02/29/2024

D-number: D0045

What is Dutch elm disease?

Dutch elm disease (DED) is a lethal fungal disease of native North American elms. The fungi that cause DED entered the United States early in the 1900’s on elm logs imported from Europe. DED now occurs throughout the United States and has led to the loss of the American elm as the premier street tree.

Dutch elm disease has led to the loss of the American elm as a street tree.

What is Dutch elm disease?

Where does Dutch elm disease come from?

DED is caused by two fungi, Ophiostoma ulmi and Ophiostoma novo-ulmi. These fungi are thought to have originated in Asia and were spread as elm trees and wood were moved from location to location. Once these fungi are introduced into an area, they are moved to healthy trees by two species of elm bark beetles (one native, one of European origin). These beetles breed in stressed trees (which include those trees suffering from DED), then carry spores of the DED fungi to healthy trees and inoculate the trees as they feed. Once DED fungi gain entry into an elm, they can move to other nearby elms underground via root grafts. Human activities such as pruning can lead to spread of these fungi as well.

How do I save a tree with Dutch elm disease?

Elms suffering from DED should be removed. Prior to removal, disrupt root grafts between the infected elm and other nearby healthy elms using a mechanical trencher or vibratory plow. If you do not disrupt root grafts, removal of the infected tree may accelerate movement of DED fungi through root grafts to adjacent trees. Destroy wood from diseased elms by burning (where allowed by local ordinance) or burying it. If you decide to keep the wood, remove the bark, then pile the wood and cover it with a heavy tarp, burying the tarp edges with soil, until the wood is used. Covering the wood limits access by elm bark beetles that potentially could pick up DED fungi from the cut wood and move them to other trees.

Discoloration of wood just under the bark of elm branches can indicate the presence of one of the DED fungi.

If you decide not to remove an infected elm, at least remove, then bury or burn, dead or dying branches. Make cuts six feet below any area showing symptoms. Disinfect cutting tools between each cut by treating them for at least 30 seconds with a 10% bleach solution or (preferably due to its less corrosive properties) 70% alcohol (e.g., rubbing alcohol or certain spray disinfectants). If you use bleach, be sure to thoroughly rinse and oil your tools after pruning to prevent rusting.

How do I avoid problems with Dutch elm disease in the future?

Fungicide injections of either propiconazole or thiabendazole can be useful for protecting high value, healthy American elm trees. Such injections are of limited use if trees are already infected. For best results, trees should be treated every two years by a certified arborist with additional training in making injection treatments.

If you decide to plant an elm, use non-native hybrid elms, such as “Accolade”, “New Horizon”, “Regal” and “Frontier”, that are resistant to DED. DED resistant American elm varieties are also currently available. Look for varieties such as “American Liberty”, “Independence”, “Princeton”, “New Harmony” and “Valley Forge” at your local nursery or garden center. Keep in mind however that resistance is not immunity, and even DED-resistant elm varieties can become infected. Typically however, in resistant varieties, DED does not develop as rapidly, providing time and opportunity to attempt to manage the disease using other strategies (e.g., pruning, fungicide injections).

For more information on Dutch elm disease:

Contact the University of Wisconsin Plant Disease Diagnostics Clinic (PDDC) at (608) 262-2863 or pddc@wisc.edu.

This Fact Sheet is also available in PDF format:

Full Color PDF

*Completed as partial fulfillment of the requirements for a BS in Plant Pathology at the University of Wisconsin Madison

Thanks to Lis Friemoth, Ann Joy and Laura Jull for reviewing this document.

A complete inventory of UW Plant Disease Facts is available at the University of Wisconsin-Madison Plant Disease Diagnostics Clinic website: https://pddc.qa.webhosting.cals.wisc.edu.

Submit additional lawn, landscape, and gardening questions at https://hort.extension.wisc.edu/ask-a-gardening-question/.

Disease - Broad Leafed Woody Ornamental, Disease - Field and Forage, Disease - Fruit Crop, Disease - Herbaceous Ornamental, Disease - Specialty Crop, Disease - Vegetable

Downy Mildew

July 21, 2015 hudelson

UW Plant Disease Facts

Authors: Jim Olis* and Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 02/29/2024

D-number: D0044

What is downy mildew?

The downy mildews are a group of diseases that cause destruction of the leaves, stems, flowers and fruits of many plant species worldwide. In Wisconsin, downy mildews have traditionally been problems on grapes, cucumbers (see UW Bulletin A3978, Cucurbit Downy Mildew: Identification and Management, available at https://learningstore.extension.wisc.edu/), roses and Viburnum. Downy mildews on basil (see UW Plant Disease Facts D15, Basil Downy Mildew) and impatiens (see UW Plant Disease Facts D66, Impatiens Downy Mildew) have more recently become problematic.

What does downy mildew look like?

Downy mildew symptoms begin as small, green or yellow, translucent spots that can eventually spread to an entire leaf, stem, flower or fruit. Infected plant parts may eventually brown or bronze. The causal organism appears on infected stems, flowers and fruits, and on undersurfaces of infected leaves, as a downy, white, gray or purple fuzz.

Where does downy mildew come from?

Downy mildew is caused by several closely related fungus-like water molds (e.g., Peronospora spp., Plasmopara spp. and Pseudoperonospora spp.) that survive in plant debris or on infected plants. Downy mildew organisms are fairly host specific. The downy mildew organism that infects one type of plant (e.g., rose) is not the same downy mildew organism that infects another (e.g., grape). However, if you see downy mildew on one plant, then environmental conditions (i.e., cool, wet weather) are favorable for development of downy mildews on a wide range of plants.

How do I save a plant with downy mildew?

Downy mildews can be controlled using fungicides, if treatments are applied early enough in disease development. Fungicides containing chlorothalonil and copper (particularly Bordeaux mix, a combination of copper sulfate and lime) are labeled for downy mildew control in home gardens. Timing and number of applications will vary depending on exactly the type of downy mildew you are attempting to control. Be sure to read and follow all label instructions of the fungicide that you select to ensure that you use the product in the safest and most effective manner possible.

How do I avoid problems with downy mildew in the future?

Consider buying downy mildew resistant varieties, when available. In new plantings, space plants far apart. In established plantings, prune or thin plants to increase airflow. Proper spacing and thinning will reduce humidity and promote rapid drying of foliage, which is less favorable for downy mildew development. Avoid overhead watering and apply water directly to the soil at the base of your plants. At the end of the growing season, remove and destroy infected plant debris as this can serve as a source of spores for the next growing season.

For more information on downy mildew:

Contact the University of Wisconsin Plant Disease Diagnostics Clinic (PDDC) at (608) 262-2863 or pddc@wisc.edu.

This Fact Sheet is also available in PDF format:

Full Color PDF

*Completed as partial fulfillment of the requirements for a BS in Plant Pathology at the University of Wisconsin Madison.

Thanks to Lisa Johnson, Ann Joy and Kristin Kleeberger for reviewing this document.

A complete inventory of UW Plant Disease Facts is available at the University of Wisconsin-Madison Plant Disease Diagnostics Clinic website: https://pddc.qa.webhosting.cals.wisc.edu.

Submit additional lawn, landscape, and gardening questions at https://hort.extension.wisc.edu/ask-a-gardening-question/.

Disease - Needled Woody Ornamental

Dothistroma Needle Blight

July 21, 2015 hudelson

UW Plant Disease Facts

Authors: Jim Olis* and Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 02/29/2024

D-number: D0043

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.

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 the product 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).

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. Consider using other conifers 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:

Contact the University of Wisconsin Plant Disease Diagnostics Clinic (PDDC) at (608) 262-2863 or pddc@wisc.edu.

This Fact Sheet is also available in PDF format:

Full Color PDF

*Completed as partial fulfillment of the requirements for a BS in Plant Pathology at the University of Wisconsin Madison.

Thanks to Ann Joy, Laura Jull and Patti Nagai for r eviewing this document.

A complete inventory of UW Plant Disease Facts is available at the University of Wisconsin-Madison Plant Disease Diagnostics Clinic website: https://pddc.qa.webhosting.cals.wisc.edu.

Submit additional lawn, landscape, and gardening questions at https://hort.extension.wisc.edu/ask-a-gardening-question/.

Disease - Broad Leafed Woody Ornamental, Disease - Field and Forage, Disease - Fruit Crop, Disease - Herbaceous Ornamental, Disease - Needled Woody Ornamental, Disease - Vegetable, Misc, Turf

Dodder

July 21, 2015 hudelson

UW Plant Disease Facts

Authors: Jennifer Clifford, Amilcar Sanchez, Trenton Stanger, and Brian Hudelson UW-Madison Plant Pathology

Last Revised: 02/29/2024

D-number: D0129

Spaghetti-like dodder plants parasitizing carrots.

What is dodder?

Dodder is the name of several species of parasitic plants that are widely distributed in North America and Europe. Plants parasitized by dodder include alfalfa, carrots, onions, potatoes, cranberries, a variety of herbaceous and woody ornamentals, and many weed species. Parasitized plants become weakened, have reduced yields (in the case of agronomic crops), and can potentially die.

What does dodder look like?

Dodders lack roots and leaves, and also lack chlorophyll, the green pigment found in most plants. Dodders have slender, yellow-orange stems that cover infected plants in a spreading, tangled, spaghetti-like mass. From May through July, dodders produce white, pink, or yellowish flowers.

Where does dodder come from?

Dodders produce large numbers of seeds that germinate in the spring to produce shoots that attach to suitable host plants. Dodders penetrate host tissue, and absorb nutrients via specialized structures called haustoria. Once established on a host, the bottom of a dodder plant dies (thereby severing its connection with the soil), and the dodder plant becomes dependent on the host plant for water and nutrients.

How do I save plants parasitized by dodder?

On woody ornamentals, simply prune out dodder-parasitized branches. When small patches of dodder occur among herbaceous plants, apply contact herbicides such as 2,4-D early in the season, preferably before dodder seedlings have parasitized host plants. Keep in mind that use of contact herbicides will likely also kill host plants. Alternatively, cut or burn dodder and parasitized plants to keep dodder from spreading, and to prevent seed production. For widespread dodder infestations, a combination of frequent tilling, burning and herbicide applications may be needed to achieve control. Be sure to read and follow all label instructions of the herbicide that you select to ensure that you use the product in the safest and most effective manner possible.

How do I avoid problems with dodder in the future?

Dodder’s wide host range and ability to survive as dormant seeds in soil make eradication difficult. Preventing introduction of dodder is the best method of control. Use dodder-free seed, and be sure to clean equipment thoroughly after working in a dodder-infested area. Try to restrict animal movement between infested and non-infested areas as well. Depending upon the specific crop or location, use of pre-emergent herbicides containing DCPA, dichlobenil, propyzamide, or trifluralin may be possible to prevent germination of dodder seeds. Destroy actively growing dodder and any parasitized plants before the dodder produces seeds. In agricultural settings where dodder has been a problem, rotate away from susceptible crops and grow non-host crops (e.g., corn, soybeans, or small grain cereals). In conjunction with rotation, adequate control of weed hosts is critical to achieve control.

For more information on dodder:

Contact the University of Wisconsin Plant Disease Diagnostics Clinic (PDDC) at (608) 262-2863 or pddc@wisc.edu.

This Fact Sheet is also available in PDF format:

Full Color PDF

Thanks to Lis Friemoth, Matt Lippert and Dan O’Neil for reviewing this document.

A complete inventory of UW Plant Disease Facts is available at the University of Wisconsin-Madison Plant Disease Diagnostics Clinic website: https://pddc.qa.webhosting.cals.wisc.edu.

Submit additional lawn, landscape, and gardening questions at https://hort.extension.wisc.edu/ask-a-gardening-question/.

Disease - Broad Leafed Woody Ornamental, Disease - Fruit Crop, Misc

Dead Man’s Fingers

July 19, 2015 hudelson

UW Plant Disease Facts

Authors: Ann Joy and Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 02/29/2024

D-number: D0040

What is dead man’s fingers?

Dead man’s fingers are mushroom-like fungal growths that can be found at the base of dead or dying trees and shrubs, as well as at the base of wood objects (e.g., wood barrels) that are in contact with soil. Some types of dead man’s fingers are produced by wood-decomposing fungi. Others are produced by fungi that cause black root rot. This disease typically is a problem on stressed trees or shrubs, including apple, crabapple, pear, cherry, plum, American elm, Norway maple and honeylocust.

Dead man’s fingers growing from mulch next to a barrel planter. (Photo courtesy of Dick Becker)

What does dead man’s fingers look like?

The most recognizable dead man’s fingers are those that are black and club-shaped with a white interior, appearing as solitary or clustered irregularly-shaped “fingers” that are approximately 1½ to 4 inches tall. They form on or near dead or dying wood. In the spring, as the “fingers” first form, they may be pale blue with white tips. Disease-causing species of the fungus initially form a pale sheath around roots that later becomes black and crusty, hiding a lighter interior. This sheath/crust is sometimes visible when soil is brushed away from tree/shrub roots. Trees/shrubs with above-ground symptoms of infection may show decline, dieback, slowed growth, and basal cankers. Infected apple trees may produce an abnormally large crop of smaller than normal-sized fruits.

Where does dead man’s fingers come from?

Dead man’s fingers are sexual reproductive structures of fungi in the genus Xylaria. Sexual spores (called ascospores) are produced inside each club-like “finger” and released through a tiny hole in the top. The “fingers” can release these spores for several months or years. In the spring, Xylaria can produce asexual spores (called conidia) anywhere on its surface. Xylaria also produces threadlike structures (called hyphae) that grow through dead or dying wood. Xylaria can survive as hyphae in roots for up to 10 years, and can spread from plant to plant via hyphae when plant roots come in contact with each other.

How can I save a tree with dead man’s fingers?

In urban settings, dead man’s fingers may grow from wood mulch and may not be an indication of disease. Simply remove and discard the “fingers” if you find them unsightly. If dead man’s fingers form around or near the base of an apple, crabapple or other known susceptible host, the fungus may be infecting the tree, causing black root rot. In this situation, by the time the characteristic “fingers” appear, the infection is well advanced. An infected tree should be carefully removed, including the stump and as much of the root system as possible. DO NOT use wood from Xylaria-infected trees for mulch. There are no fungicides registered in Wisconsin for treatment of black root rot.

How can I prevent dead man’s fingers from being a problem in the future?

DO NOT plant susceptible trees or shrubs in a site where dead man’s fingers has been observed. In addition, make sure that susceptible trees/shrubs in other locations are well watered, fertilized, mulched and otherwise maintained to reduce stresses that might predispose them to infection by disease-causing species of Xylaria. Unfortunately, Xylaria-resistant tree and shrub varieties/cultivars are not available.

For more information on dead man’s fingers:

Contact the University of Wisconsin Plant Disease Diagnostics Clinic (PDDC) at (608) 262-2863 or pddc@wisc.edu.

This Fact Sheet is also available in PDF format:

Full Color PDF

Thanks to Jane Anklam, Mark Kopecky and Judy Reith – Rozelle for reviewing this document.

A complete inventory of UW Plant Disease Facts is available at the University of Wisconsin-Madison Plant Disease Diagnostics Clinic website: https://pddc.qa.webhosting.cals.wisc.edu.

Submit additional lawn, landscape, and gardening questions at https://hort.extension.wisc.edu/ask-a-gardening-question/.

Disease - Herbaceous Ornamental

Daylily Leaf Streak

July 19, 2015 hudelson

UW Plant Disease Facts

Authors: Megan Meyers* and Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 02/29/2024

D-number: D0039

What is leaf streak?

Leaf streak is a common disease of daylilies, affecting daylilies wherever they are grown. Daylily varieties can vary widely in terms of their susceptibility to the disease. Oftentimes leaf streak is a cosmetic problem, causing little damage. In some cases however, leaf streak can cause substantial leaf loss, and rarely, it may lead to complete defoliation of daylily plants.

Yellowing and browning of leaves typical of daylily leaf streak. (Photo courtesy of Doug Maxwell)

What does leaf streak look like?

Leaf streak symptoms often initially appear as yellowing that begins at leaf tips and spreads down along and outward from the midveins of leaves. This tissue eventually browns and dies. Red-brown flecks may also be a symptom of leaf streak. These flecks enlarge, turn brown and become surrounded by yellow halos. As the disease progresses, complete leaf death can occur.

Where does leaf streak come from?

Leaf streak is caused by the fungus Aureobasidium microstictum. This fungus overwinters in daylily leaf debris where it produces spores that initiate the disease each spring. Spores produced on infected leaves lead to additional infections. The disease is most common in warm, wet weather.

How do I save a plant with leaf streak?

Remove infected leaves as they appear, and fertilize and water your plants properly to promote growth of new leaves. DO NOT water with a sprinkler. This can spread the leaf streak fungus, as well create conditions more favorable for infection. Instead, use a soaker or drip hose to apply water directly into the soil. To further limit pathogen spread, avoid working with plants when they are wet.

How do I avoid problems with leaf streak in the future?

Remove dead leaves from daylilies each fall to eliminate a source of the leaf streak fungus. Burn (where allowed by local ordinance), deep bury or hot compost this material. As daylily plants grow, divide them into smaller clumps, and replant them with ample space between clumps. This will improve air circulation and promote more rapid leaf drying. Consider using daylily varieties (e.g., ‘Betty Bennet’, ‘Edna Spalding’, ‘Ella Pettigrew’, ‘Globe Trotter’, ‘Nancy Hicks’, ‘Pink Superior’, ‘Ron Rousseau’, ‘Sudie’, ‘Tropical Tones’, ‘Upper Room’, ‘Winsome Lady’) with reported leaf streak resistance. Keep in mind however, that resistant varieties may not perform well every year and under all environmental conditions. If you grow daylily varieties that have severe leaf streak every year, consider applying fungicides containing chlorothalonil, mancozeb or thiophanate-methyl to prevent the disease. Use fungicides only during periods of wet weather. Start applications before you see symptoms and treat every seven to 14 days as long as wet weather persists. DO NOT use the same active ingredient for all treatments, particularly if you decide to use thiophanate-methyl. Alternate use of at least two active ingredients to help minimize problems with fungicide-resistant strains of the leaf streak pathogen. Be sure to read and follow all label instructions of the fungicides that you select to ensure that you use them in the safest and most effective manner possible.

For more information on daylily leaf streak:

Contact the University of Wisconsin Plant Disease Diagnostics Clinic (PDDC) at (608) 262-2863 or pddc@wisc.edu.

This Fact Sheet is also available in PDF format:

Full Color PDF

*Completed as partial fulfillment of the requirements for a BS in Plant Pathology at the University of Wisconsin Madison.

Thanks to Heidi Doering, Doug Maxwell and Ann Wied for reviewing this document.

A complete inventory of UW Plant Disease Facts is available at the University of Wisconsin-Madison Plant Disease Diagnostics Clinic website: https://pddc.qa.webhosting.cals.wisc.edu.

Submit additional lawn, landscape, and gardening questions at https://hort.extension.wisc.edu/ask-a-gardening-question/.

Disease - Herbaceous Ornamental, Disease - Vegetable

Damping-Off

July 19, 2015 hudelson

UW Plant Disease Facts

Authors: Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 02/29/2024

D-number: D0038

What is damping-off?

Damping-off is a common and fatal disease that affects all types of plant seedlings. The disease is most prevalent when seeds are germinated in cool, wet soils. Fortunately, seedlings are susceptible to damping-off for only a short period following emergence. As plants age, their susceptibility to damping-off declines.

Lower stem collapse of Zinnia seedlings due to damping-off.

What does damping-off look like?

Seedlings killed by damping-off initially are healthy but shortly after emergence become infected at or just below the soil line. The lower stems of the seedlings collapse, and the seedlings fall over onto the soil surface. The seedlings subsequently die.

Where does damping-off come from?

Damping-off is caused by several soil-borne water molds and fungi, including (but not limited to) Pythium spp., Rhizoctonia solani and Fusarium spp. These organisms readily survive and are moved in soil or on soil-contaminated items such as pots, tools and workbenches.

How do I save seedlings with damping-off?

Seedlings with damping-off will die and cannot be saved. Proper prevention is the only way to avoid problems with this disease.

How do I avoid problems with damping-off in the future?

When planting seeds, make sure that work areas, tools and pots are pathogen-free. Decontaminate tools and workbenches by treating them for at least 30 seconds with 10% bleach or (preferably due to its less corrosive properties) 70% alcohol (e.g., rubbing alcohol or certain spray disinfectants). Decontaminate pots by washing them with soapy water to remove bits of old soil, soaking them for at least 20 minutes in 10% bleach, and then rinsing them thoroughly to remove bleach residues. DO NOT reuse plastic pots if you have had problems with damping-off or root rots (see UW Plant Disease Facts D0095, Root Rots in the Garden, for details) in the past, as they are difficult to decontaminate.

When planting, use a well-drained, pasteurized potting mixture. DO NOT use garden soils as they often contain damping-off pathogens. DO NOT plant seeds too deeply, and germinate seeds at high temperatures, so that seedlings rapidly grow out of the stage where they are susceptible to damping-off. DO NOT overwater as damping-off organisms are more active in wet soils. If the techniques described above do not work, then consider using fungicide-treated seed. In particular, plants grown from captan-treated seeds tend to have fewer problems with damping-off.

For more information on damping-off:

Contact the University of Wisconsin Plant Disease Diagnostics Clinic (PDDC) at (608) 262-2863 or pddc@wisc.edu.

This Fact Sheet is also available in PDF format:

Full Color PDF

Thanks to Lis Friemoth, Ann Joy and Ann Wied for reviewing this document.

A complete inventory of UW Plant Disease Facts is available at the University of Wisconsin-Madison Plant Disease Diagnostics Clinic website: https://pddc.qa.webhosting.cals.wisc.edu.

Submit additional lawn, landscape, and gardening questions at https://hort.extension.wisc.edu/ask-a-gardening-question/.

Disease - Needled Woody Ornamental

Cytospora Canker

July 19, 2015 hudelson

UW Plant Disease Facts

Authors: Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 02/29/2024

D-number: D0037

What is Cytospora canker?

Cytospora canker is one of the most common fungal diseases of Colorado blue spruce. This disease can also affect Engelmann, Norway and white spruce, as well as balsam fir, Douglas-fir, European larch, tamarack, and white pine. Trees that are 15 years old or older and are at least 20 feet high often show symptoms of Cytospora canker. Cytospora canker can kill trees, but more often simply makes trees so unsightly that owners opt to remove the trees.

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, although individual upper branches may show symptoms as well. Needles on infected branches turn purple, then brown. Diseased needles eventually fall off, and infected branches die. Infected branches often ooze a bluish-white sap somewhere along their length.

Where does Cytospora canker come from?

Cytospora canker is caused by the fungus Cytospora kunzei (also sometimes referred to as Leucocytospora kunzei or Leucostoma kunzei). The fungus survives in infected branches and spores are spread by wind, rain splash, insects, birds, and mammals.

How do I save a tree with Cytospora canker?

Immediately remove and destroy any diseased branches by pruning them using the three-point method of pruning (see University of Wisconsin Garden Facts XHT1014, How to Properly Prune Deciduous Trees, for details). Prune only in dry weather. Between cuts, decontaminate pruning tools by treating them for at least 30 seconds in 10% bleach or (preferably due to its less corrosive properties) 70% alcohol (e.g., rubbing alcohol, certain spray disinfectants). Decontaminating tools will help prevent movement of Cytospora kunzei from branch to branch and from tree to tree during pruning. If you use bleach, be sure to thoroughly rinse and oil tools after pruning to prevent rusting.

Bluish-white ooze often is present on branches affected by Cytospora canker.

How do I avoid problems with Cytospora canker in the future?

Perhaps the easiest way to avoid Cytospora canker is through proper tree selection, planting and maintenance. Avoid planting full-sized varieties of trees susceptible to Cytospora canker, particularly full-sized varieties of blue spruce. Instead plant dwarf tree varieties. Smaller trees will have canopies where air will more easily penetrate into the interior, thus drying branches and needles more rapidly. In general, a drier environment is less favorable for disease development. If you choose to plant a full-sized tree, leave adequate space between the tree and other trees in your landscape. Proper spacing will provide good air flow and again promote drier conditions that are less favorable for disease. Optimally, when trees are full sized, they should be far enough apart so that branches do not overlap. As a tree becomes well established, selectively prune branches to open up the tree’s canopy to further promote a drier environment.

Also minimize environmental stresses to any tree susceptible to Cytospora canker. Prevent water stress by avoiding soil compaction and by ensuring adequate soil drainage. During dry periods, make sure your tree receives approximately one inch of water per week either from natural rain or by applying supplemental water at the drip line of the tree (i.e., the edge of where tree branches extend) and beyond using a soaker or drip hose. To help maintain proper soil moisture, mulch out to at least the drip line of the tree. Use one to two inches of mulch on a heavier, clay soil; use three to four inches of mulch on a lighter, sandy soil. DO NOT pile mulch against the trunk of the tree; keep mulch approximately four inches from the trunk. Prevent nutrient stress by properly fertilizing your tree based on a soil fertility test provided by an accredited lab.

DO NOT use fungicide treatments for Cytospora canker control; fungicide treatments are not effective.

For more information on Cytospora canker:

Contact the University of Wisconsin Plant Disease Diagnostics Clinic (PDDC) at (608) 262-2863 or pddc@wisc.edu.

This Fact Sheet is also available in PDF format:

Full Color PDF

Thanks to Diana Alfuth, Jean Ferdinandsen, Lisa Johnson, Amy Sausen and Ann Wied for reviewing this document.

A complete inventory of UW Plant Disease Facts is available at the University of Wisconsin-Madison Plant Disease Diagnostics Clinic website: https://pddc.qa.webhosting.cals.wisc.edu.

Submit additional lawn, landscape, and gardening questions at https://hort.extension.wisc.edu/ask-a-gardening-question/.

Disease - Broad Leafed Woody Ornamental, Disease - Fruit Crop, Disease - Herbaceous Ornamental, Disease - Vegetable

Crown Gall

July 19, 2015 hudelson

UW Plant Disease Facts

Authors: Ann Joy and Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 02/29/2024

D-number: D0035

What is a crown gall?

Crown gall is the most widely distributed bacterial disease of plants in the world, affecting over 100 species of fruit crops, and woody and herbaceous ornamentals, including rose, euonymus, lilac, poplar, viburnum, willow, apple, pear, brambles, stone fruits and grapes. Crown gall can cause severe damage on young plants, while mature woody plants with the disease may show no ill effects.

Crown gall leads to tumor-like growths that form at or near the soil line.

What does crown gall look like?

Crown gall gets its name from the round or irregularly shaped tumor-like growths (i.e., galls) that usually form on plant crowns just above or below the soil line. Galls can also form on roots, stems, trunks, or branches. Galls can be pea-sized, or as large as several inches in diameter. Galls interfere with water transport within the plant. Therefore, affected plants may suffer from water or nutrient deficiencies, becoming stunted. Flower and fruit production may also be reduced.

Where does crown gall come from?

Crown gall is caused primarily by the bacteria Agrobacterium tumefaciens, as well as (on grape) by A. vitis. Both bacteria survive in soil and in (or on) susceptible plant roots. The bacterium is spread through movement of contaminated soil, water and infected plant material. The bacterium enters plants through wounds (e.g., mechanical injuries including pruning cuts, freeze injury, and nematode feeding sites) or natural plant openings (e.g., lenticels) and stimulates plant cells to undergo unregulated growth, leading to gall formation. Once galls begin to form, they can continue to enlarge even if the bacterium is no longer present. Galls become visible anywhere from several weeks to one or more years after the time of infection.

How do I save a plant with crown gall?

There is no cure for crown gall once galls begin to form. Galls can be pruned away, but new galls may reform elsewhere on the plant. To prevent spread of the crown gall bacterium, remove infected plants, surrounding soil, and as many of the infected plant’s roots as possible.

How do I avoid problems with crown gall in the future?

Use disease-free, winter hardy stock from a reputable nursery and inspect the roots and crowns for galls before planting. Avoid wounding plants during transplant and cultivation. Decontaminate tools, equipment and shoes with 10% bleach or 70% alcohol for at least 30 seconds to prevent spread of the bacterium. Use of a biological control product can prevent A. tumefaciens infections at the time of planting. Current biological control products contain A. radiobacter, a close relative of the crown gall organism. These products are not effective on all hosts, or against all variants of the pathogen. In areas with infested soil, rotation to a non-susceptible plant (such as grass) for 3 years, may provide a good means of disease control. In commercial settings, soil fumigation may provide limited control of the crown gall bacterium in soil. However, fumigation does not kill the bacterium in roots that remain in the soil after removal of infected plants. Fumigation is not recommended for homeowners.

For more information on crown gall:

Contact the University of Wisconsin Plant Disease Diagnostics Clinic (PDDC) at (608) 262-2863 or pddc@wisc.edu.

This Fact Sheet is also available in PDF format:

Full Color PDF

Thanks to Diana Alfuth, Paul Hartman, and Patty McManus for reviewing this document.

A complete inventory of UW Plant Disease Facts is available at the University of Wisconsin-Madison Plant Disease Diagnostics Clinic website: https://pddc.qa.webhosting.cals.wisc.edu.

Submit additional lawn, landscape, and gardening questions at https://hort.extension.wisc.edu/ask-a-gardening-question/.


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