All posts by hudelson

Disease - Broad Leafed Woody Ornamental, Disease - Fruit Crop

Apple Scab

November 19, 2018 hudelson

UW Plant Disease Facts

Authors: Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 02/28/2024

D-number: D0004

What is apple scab?

Apple scab is a potentially serious fungal disease of ornamental and fruit trees in the rose family. Trees that are most commonly and severely affected include crabapple, hawthorn, mountain-ash, apple and pear. In ornamental trees, leaf loss caused by apple scab can make trees unsightly and aesthetically unappealing. In fruit trees, leaf loss can reduce fruit yield. In addition, the presence of apple scab on fruits can make the fruit difficult, if not impossible, to market.

Leaf spots typical of apple scab on apple. Typical apple scab leaf spots (left) and fruit lesions (right). The disease can cause total defoliation and make fruit unmarketable.

What does apple scab look like?

Apple scab lesions (diseased areas) are often first noticed on leaves, where they most commonly occur on the upper leaf surface. Fruits are also very susceptible to infection. Lesions on both leaves and fruits are roughly circular with feathery edges and have an olive green to black color. Lesions can be as small as the size of a pinhead or as large a ½ inch in diameter. When disease is severe, lesions can merge and cover a large portion of the leaf or fruit surface. Defoliation of a tree (i.e., extensive leaf drop) often follows.

Where does apple scab come from?

Scab is caused primarily by the fungus Venturia inaequalis. Other species of Venturia can be involved in diseases similar to apple scab. In particular, Venturia pirina causes a very similar disease (called pear scab) on pear. Venturia inaequalis and its relatives survive the winter in leaf litter from infected trees. Scab is most severe in cool, wet years.

How do I save a tree with apple scab?

Apple scab is not a lethal disease, even when trees totally defoliate. Once symptoms are visible, it is too late to treat a tree. Proper long-term management of apple scab is important however. If left unchecked, defoliation due to apple scab year after year can stress a tree and make it more susceptible to other, more serious and lethal diseases and insect pests.

How do I avoid problems with apple scab in the future?

If your crabapple, apple or pear tree has a history of severe scab, consider replacing it with a resistant variety. See UW Bulletins A2105 (Apple Cultivars for Wisconsin), A2488 (Home Fruit Cultivars for Northern Wisconsin), and A2582 (Home Fruit Cultivars for Southern Wisconsin) for recommendations. These publications are all available at https://learningstore.extension.wisc.edu/.

If you have a susceptible tree that you want to maintain, carefully collect up and discard fallen, infected leaves each autumn. These leaves are a major source of spores that can infect leaves the following growing season. Also, be sure to routinely thin your trees to open up the canopy and allow better airflow. Thinning will promote more rapid drying of leaves, which is less favorable for apple scab development.

Even with proper fall leaf clean up and thinning, you may have to consider applying fungicide treatments to susceptible trees, particularly when the weather is cool and wet. Captan, chlorothalonil, mancozeb, myclobutanil, propiconazole, or thiophanate methyl, are available for apple scab control, although not all of these active ingredients can be used on trees where fruit will eventually be eaten. Be sure to read and follow all label instructions of the fungicide(s) that you select to ensure that you use the correct fungicide(s) in the safest and most effective manner possible. Typically, you will need to treat every seven to 14 days from bud break until wet weather subsides. DO NOT use myclobutanil, propiconazole, or thiophanate methyl as the sole active ingredient for all treatments. If you decide to use one of these active ingredients, alternate its use with at least one of the other active ingredients listed above to help minimize problems with fungicide-resistant strains of the apple and pear scab fungi.

For more information on apple scab:

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 Paul Hartman, Laura Jull, Patti Nagai and Scott Reuss 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.wisc.edu.

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

Disease - Broad Leafed Woody Ornamental

Eastern Filbert Blight

December 21, 2016 hudelson

UW Plant Disease Facts

Authors: Kaitlin Morey Gold*, UW-Madison Plant Pathology

Last Revised: 02/29/2024

D-number: D0047

What is Eastern filbert blight?

Eastern filbert blight is a potentially serious fungal disease found throughout the United States, including Wisconsin. It affects only Corylus species, commonly known as hazelnuts or filberts. On hazelnuts native to Wisconsin such as American hazelnut (Corylus americana) and beaked hazelnut (Corylus cornuta), the disease causes little significant damage, but on the commonly grown European hazelnut (Corylus avellana), including Harry Lauder’s walking stick (Corylus avellana ‘Contorta’), the disease is lethal. Turkish filbert (Corylus colurna) also appears to be highly susceptible.

Eastern filbert blight can cause small black cankers that form in rows, or deep gouges in the bark of severely infected trees/shrubs.

What does Eastern filbert blight look like?

Eastern filbert blight causes cankers (i.e., dead, collapsed areas) on branches or main trunks. Easily visible within the cankers are black, football-shaped stromata (the reproductive structures of the causal fungus). The stromata often form in rows of two. Cankers first appear on new twigs and expand over time. American hazelnut trees/shrubs are able to live almost indefinitely with Eastern filbert blight, forming a small number of slowly-expanding cankers (if any cankers form at all) that lead to limited branch dieback. On European hazelnut however, cankers will expand anywhere from one inch to three feet in a year, and can eventually form long, deep gouges or grooves on severely affected trees/shrubs. European hazelnuts typically die due to girdling from Eastern filbert blight within five to 10 years of initial infection.

Where does Eastern filbert blight come from?

Eastern filbert blight is caused by the fungus Anisogramma anomala. Stromata formed by the fungus produce spores that are spread short distances by water splash and over longer distances by wind. Humans also can spread Anisogramma anomala on their hands and clothing, on gardening tools, and by transporting wood from infected trees/shrubs. Unlike other canker fungi that infect through wounds, the Eastern filbert blight fungus primarily infects through immature tissue on actively growing shoots. Cankers appear 12 to 18 months after infection. Eastern filbert blight does not affect hazelnut leaves, fruits or nuts.

How do I save trees/shrubs with Eastern filbert blight?

There is no cure for Eastern filbert blight. If only a few branches on a tree/shrub are affected, prune these branches two to three feet below each canker. Decontaminate tools after 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, certain spray disinfectants).

If a tree/shrub is severely affected by Eastern filbert blight (e.g., when there are so many cankers on multiple branches that the tree/shrub would look ugly if pruned, when branch pruning would require removing part of the trunk, or when trunk cankers are present), removal of the tree/shrub is the preferred management strategy.

Pruned branches and removed trees/shrubs should be burned (where allowed by local ordinance), deep-buried, or chipped (as long as the chips are allowed to dry to kill the Eastern filbert blight fungus).

How do I avoid problems with Eastern filbert blight in the future?

Consider planting native species of hazelnut (e.g., American and beaked hazelnut) that are naturally resistant to the disease. If you decide to plant European hazelnut, select cultivars that have been bred for resistance. ‘Jefferson’, ‘Santiam’, ‘Yamhill’, and ‘Theta’ are resistant, nut-bearing cultivars. ‘Red Dragon’ is a resistant, ornamental cultivar. Note that these cultivars are not hardy in all hardiness zones in Wisconsin. Hybrid hazelnuts (crosses between American and European hazelnut) are becoming increasingly available, but should be used with caution because their susceptibility to Eastern filbert blight has not been adequately tested.

Once hazelnut trees/shrubs are established in your yard, routinely inspect the plants for infection and remove infected branches as they occur. Watch for dying branches in the summer and cankers (particularly on or near the youngest growth) in the winter. Inspecting trees during the winter is very important, because cankers are more visible at that time.

Fungicides can be used for management, but should only be used as a last resort. Not all fungicides that are approved for Eastern filbert blight control are particularly effective, but chlorothalonil has been shown to be an effective preventative treatment, although it will not cure existing infections. Note that not all formulations of chlorothalonil are approved for use on nut-bearing hazelnuts; many formulations can only be used on ornamental hazelnuts. Therefore, if you decide to use chlorothalonil, be sure to select the appropriate formulation for your particular situation. Apply the first treatment at bud break (i.e., when half the buds show a separation of leaves) and additional treatments (up to three) every two weeks thereafter. If you plan to eat nuts from your hazelnut tree, make sure that your last fungicide treatment is applied at least 120 days before anticipated nut harvest. For further details about recommended fungicides, spray rate recommendations, and diagrams of bud stages, see Pest Management Guide for Hazelnuts in the Willamette Valley, Oregon State University Extension Bulletin EM8328 available at https://catalog.extension.oregonstate.edu/em8328.

For more information on Eastern filbert 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 Plant Pathology 558 at the University of Wisconsin Madison.

Thanks to Jason Fischbach, Benjamin Gold, Laura Jull, Marian Lund, Ryan Morey, and Mary Pelzer 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.wisc.edu.

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

Disease - Fruit Crop

Cane Blight

November 22, 2015 hudelson

UW Plant Disease Facts

Authors: David S. Jones*, UW-Madison Plant Pathology

Last Revised: 02/29/2024

D-number: D0028

What is cane blight?

Cane blight is a fungal disease that affects the health of canes (i.e., stems) of cultivated and wild Rubus species (e.g., raspberries and blackberries), wherever they are grown. Black and purple raspberries appear to be more susceptible to cane blight than red raspberries, but all commonly cultivated raspberry cultivars can get the disease. Although cane blight is not typically fatal, it may cause significant fruit yield losses if left unmanaged.

Cane death on a thornless blackberry caused by cane blight. Look for a dark brown infection line and dead/dying shoots above the point of infection. (Photo courtesy of Michael Ellis, The Ohio State University)

What does cane blight look like?

Symptoms of cane blight usually first appear in early summer after blossoming and leaf emergence, and in association with wounds caused by pruning or harvesting of fruit. Look for sudden death of side branches and tips of fruit-bearing canes, as well as dark brown or purple spots (called cankers) on the canes below the dieback. In wet weather, cankers may produce a grey ooze. In dry weather, the cankers may appear fuzzy or powdery. Dead canes may become brittle and snap off in windy conditions.

Where does cane blight come from?

Cane blight is caused by the fungus Leptosphaeria coniothyrium which survives the winter in infected canes. During wet periods, the fungus produces windborne spores and infects through open wounds on canes caused by pruning, harvest damage, insect damage, or abrasions from canes rubbing together. As the disease develops, the fungus produces additional spores that can spread to other wounds by wind and splashing water, leading to additional infections.

How do I save plants with cane blight?

DO NOT prune infected canes during the growing season as pruning wounds will provide the cane blight fungus easy entry into healthy tissue. Label symptomatic canes as you see them and prune the canes to the ground during the dormant season (i.e., mid- to late winter). Also prune any older cane stubs at this time to remove them as a source of abrasion and wounding for newer canes. Pruning when plants are dormant allows ample time for wounds to close at a time of year when spores of the cane blight fungus are not being produced. Use only sharp tools for pruning, and disinfest pruning tools after each cut 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). If you use bleach, be sure to thoroughly rinse and oil your tools after pruning to prevent rusting. Dispose of any canes that you prune by burning them (where allowed by local ordinance), burying them, or arranging to have them hauled away through municipal brush collection. Be patient as you attempt to get cane blight under control; it may take two or more years of pruning and good sanitation to reduce cane blight to negligible levels.

How can I prevent cane blight in the future?

When establishing a new raspberry patch, choose a site that is well-drained and sunny, and make sure that the distance between rows is approximately 18 inches. Also be sure to keep weeds under control. Proper site selection, row spacing and weed control will promote good airflow and drainage, and will reduce excessive moisture that is favorable for spore production by the cane blight fungus.

In addition, maintain optimum soil fertility. If you underfertilize plants, they will produce weak canes that are less able to fend off infections by the cane blight fungus. If you overfertilize plants (particularly with nitrogen), they will produce succulent new growth that is more prone to breakage and more prone to wounding by certain insects that will use the new growth as food. Remember that wounds of any kind can provide entry points for the cane blight fungus. For details on properly fertilizing raspberries, see UW Bulletin A1610, Growing Raspberries in Wisconsin (available at https://learningstore.extension.wisc.edu/).

For more information on cane 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 Plant Pathology 558 at the University of Wisconsin Madison.

Thanks to Anne Donnellan, Kris Gabert, Abigail Jones, Patty McManus, Craig Schreiner, and Lisa Schreiner 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.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 - Needled Woody Ornamental, Disease - Vegetable, Misc

Wood Mulch and Tree Health

August 20, 2015 hudelson

UW Plant Disease Facts

Authors: Jane Cummings-Carlson and John Kyhl, Wisconsin Department of Natural Resources Gina Foreman and Brian Hudelson, UW-Madison Plant Pathology
Last Revised: 03/02/2024
D-Number: D0128

What are the benefits of wood mulch?

Wood mulch is typically available as chipped wood, or shredded or chunked bark, and can contribute to tree health in many ways. When high quality, composted mulches are applied two to four inches deep in a ring three to six feet in diameter (or greater) from the trunk of a tree, mulch can help preserve moisture, control weeds, limit damage to the trunk from mowers and string trimmers and moderate the soil temperature. Use four inches of mulch when soils are light and well-drained, and two inches of mulch on heavier, clay soils.

Use of properly composted mulches can be beneficial to trees and shrubs in the landscape.

Can wood mulch harm trees?

Use of improperly composted mulches (some-times called “sour mulches”), can lead to tree nutrient deficiencies. Sour mulches can also produce gases like methane and ammonia that can be toxic to plants. Foliage on trees surrounded by sour mulches may initially turn yellow, then brown, die and fall off. If your mulch smells like vinegar, ammonia or sulfur, it is likely a sour mulch and should be removed. Replace the sour mulch with a high quality, composted mulch and consult with your local Extension agent about testing the soil for nutrient deficiencies. Fertilize appropriately based on the results of these tests.

Improper application of mulch can also lead to problems. Piling wood mulch up against the trunk of a tree can keep the bark underneath excessively wet. This wetness can contribute to bark decay. In addition, use of thick mulch layers (greater than four inches) can lead to overly wet soils that are favorable for development of root rots (see UW Plant Disease Facts D0094, Root and Crown Rot). To avoid these problems, make sure mulch is applied at least four inches away from the trunk of a tree and that the mulch layer is the appropriate thickness for the soil type in your landscape (see above).

Does woody mulch harbor or attract insects?

Insects such as earwigs [see UW Bulletin A3640, Controlling Earwigs (available at https://learningstore.extension.wisc.edu/)], centipedes (see University of Wisconsin Garden Facts XHT1113, Centipedes), millipedes (see University of Wisconsin Garden Facts XHT1108, Millipedes) and sowbugs (see University of Wisconsin Garden Facts XHT1110, Sowbugs) can feed on decaying organic matter in mulches. While these insects are often only nuisances, earwigs can feed on and cause damage to a variety of ornamentals, particularly to flowering plants. If mulch is used near entrances to a home or around basement windows, these unwanted insects may get inside. Termites ingest wood and can be attracted to wood mulch, but new termite colonies are not likely to become established due to use of wood mulches. Typically, termites are not a problem in Wisconsin, and when colonies are found, they occur only in the southern half of the state.

Carpenter ants [see UW Bulletin A3641, Controlling Carpenter Ants (available at https://learningstore.extension.wisc.edu/)] and powderpost beetles (see University of Wisconsin Garden Facts XHT1053, Powderpost Beetles) are unlikely to utilize mulch as a food source because conditions required for their development would not be satisfied by wood mulch. Carpenter ants do not ingest wood as a food source; instead, they chew non-living wood (in trees or landscape timbers, etc.) to excavate galleries in which they live and raise their young. Since wood mulch is composed of small wooden pieces, it would not serve as a home. To avoid potential insect problems, keep mulch as far away from the foundation of your home as possible and seal all holes and crevices that insects might use as entry points. Also, periodically inspect landscape timbers and the house for termites.

Does woody mulch harbor tree pathogens?

Wood mulch may come from many sources, including trees and shrubs that have died from a wide range of diseases. To be harmful to your trees, disease-causing organisms (pathogens) would have to survive in mulch and these organisms would have to move from the mulch either directly, or through the soil, to their new host – your tree. There is currently very little research on this topic.

Elm trees killed by Dutch elm disease (see UW Plant Disease Facts D0045, Dutch Elm Disease), can serve as breeding areas for native and European elm bark beetles. Bark beetles that breed in logs or firewood from these trees can pick up the fungi that cause Dutch elm disease (Ophiostoma ulmi and Ophiostoma novo-ulmi) and carry these fungi from tree to tree. Chipping infected elm trees creates an unfavorable environment for bark beetles yet there is no scientific literature that describes the level of risk of transmitting the Dutch elm disease fungi from wood chips or bark chunks to healthy elms.

Oak trees killed by oak wilt (see UW Plant Disease Facts D0075, Oak Wilt) can be attractive to several sap-feeding beetles that can potentially pick up the oak wilt fungus (Bretziella fagacearum) and move it in the landscape. This process is affected by moisture and temperature and would likely be disrupted by the chipping and composting process yet there is no scientific literature that describes the level of risk of transmitting the oak wilt disease fungus from wood chips or bark chunks to healthy oaks.

Research at the University of Wisconsin-Madison suggests that wood chip mulches produced from trees suffering from Verticillium wilt (see UW Plant Disease Facts D0121, Verticillium Wilt of Trees and Shrubs) can serve as a source of the fungus (Verticillium dahliae) that causes the disease. These studies show that Verticillium can survive for at least one year in mulch and that use of this contaminated mulch can lead to Verticillium wilt in both woody and herbaceous plants. Therefore use of mulches produced from trees with Verticillium wilt should be avoided.

For more information on wood mulch and tree health:

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 Ann Joy, Laura Jull and Phil Pellitteri 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.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 - Needled Woody Ornamental

Winter Burn

August 19, 2015 hudelson

UW Plant Disease Facts

Authors: Laura Jull, UW-Madison Horticulture

Last Revised: 03/02/2024

D-number: D0127

What is winter burn?

Winter burn is a common problem of evergreens including those with broad leaves (e.g., boxwood, holly, rhododendron), needles (e.g., fir, hemlock, pine, spruce, yew) and scale-like leaves (e.g., arborvitae, false cypress, juniper) grown in open, unprotected locations and exposed to severe winter conditions. Evergreen plants that are marginally hardy in a location (i.e., not well-adapted to local winter conditions) are at increased risk for winter burn. Winter burn can be so severe that affected plants may die and/or require replacement.

Browning due to winter burn on dwarf Alberta spruce.

What does winter burn look like?

Winter burn symptoms often become apparent as the snow melts and spring temperatures rise. Foliage starts to brown at the tips of branches with browning progressing inward toward the center of the plant. On broad-leaved evergreens, leaf edges typically brown first, followed by browning of entire leaves. Foliage facing south, southwest or west is most often affected. Symptomatic foliage often begins to drop off starting in spring and continuing through mid-summer as new foliage is produced. In extreme cases, entire plants can brown and die.

What causes winter burn?

There are many factors that can contribute to winter burn. In general, plants with shallow or poorly-developed root systems that do not efficiently take up water (e.g., recent transplants) are more prone to winter burn. Warm fall temperatures that delay the onset of plant dormancy can also contribute to winter burn. Under such conditions, plants are not prepared for the subsequent rapid onset of freezing winter temperatures, and as a result damage to foliage occurs. Similar cold injury can occur mid-winter when temperatures drop sharply at sunset causing foliage that has warmed during the day to rapidly cool and freeze. In addition, on sunny winter days, foliage (particularly foliage facing the sun) can begin to transpire (i.e., naturally lose water through the foliage). Because the ground is frozen, plant roots cannot take up water and replace the water that has been lost from the foliage. As a result, foliage dries and browns. Foliage under snow or facing away from the sun and direct winds is usually not damaged. Strong winter winds can lead to additional water loss making winter burn more severe. Colder than normal winter temperatures and longer than normal winters can also be factors in the development of winter burn, especially if below normal temperatures occur into April (the time of year when plants normally come out of dormancy and are most susceptible to winter injury). Finally, exposure of plants to salt used to de-ice roads, driveways and sideways during the winter can make plants more prone to winter burn injury.

How do I save a plant with winter burn?

For evergreens such as arborvitaes, boxwoods, junipers and yews, prune out dead, brown, damaged or dying tissue in mid-spring after new foliage is produced. If new foliage has not yet emerged by spring, scratch the bark on affected branches and look for green tissue underneath. Also gently peel back the bud scales to look for inner green bud tissue. If the stem or bud tissue is green, buds on the branch may still break to form new foliage. If the tissue is brown, the branch is most likely dead and you should prune the branch back to a live, lateral bud or branch. Such buds and branches may be far back inside the canopy and pruning may remove a substantial amount of the plant. Pines, spruces and firs typically produce new growth at branch tips in spring that will replace winter burn-damaged needles, and thus pruning may not be required on these evergreens. After a couple of growing seasons, new foliage will fill in the areas that were damaged. If an entire evergreen is brown, recovery is unlikely and the plant should be replaced with something (e.g., a deciduous shrub or tree) that is better-suited to the site.

How do I avoid problems with winter burn in the future?

Use a variety of strategies to prevent winter burn before winter arrives.

Plant the right plant in the right place.

Buy plants that are rated as cold hardy for your location and are well-adapted to local growing and soil conditions. Plants exposed to drying winter sun and winds are more likely to be injured. Therefore, avoid planting winter injury sensitive evergreens, particularly those that require shade or that are marginally cold-hardy, in exposed, sunny, windy areas. Plant them on the northeast or east side of a building or in a protected courtyard. Plant boxwoods, hemlocks, rhododendrons, and yews in partial shade to provide them added protection from winter sun and wind.

Plant evergreens at the right time of year.

Optimally, plant evergreens either in early spring (before buds break) or in late summer (i.e., August through September). Evergreens can be planted in the summer if you provide supplemental water. Avoid planting after early October in northern Wisconsin and after mid-October in southern Wisconsin as this will not allow sufficient time for roots to grow adequately before the ground freezes.

DO NOT prune evergreens in late summer or early fall.

Late season pruning of some non-native evergreens may encourage a flush of new growth that will not harden off properly before winter. See University of Wisconsin Garden Facts XHT1013, Pruning Evergreens, for details on when and how to prune specific evergreen trees and shrubs.

Mulch evergreens properly.

Apply two inches (on clay soils) to four inches (on sandy soils) of loose mulch (e.g., shredded hardwood, pine, or cedar bark; leaf compost; or wood chips) around the base of evergreens out to at least the drip line (e.g., the edge of where the branches extend). Keep mulch at least four inches away from the trunks of trees and the bases of shrubs. Proper mulch insulates roots from severe fluctuations of soil temperatures and reduces water loss. It also helps protect roots from injury due to heaving that occurs when soils go through cycles of freezing and thawing during the winter. Heaving can especially be a problem for shallow-rooted and newly planted evergreens. DO NOT mulch excessively or too close to plants as this can lead to damage by providing shelter for mice and voles (which can girdle trunks and branches) and by providing a favorable environment for disease development as well as insect activity and feeding.

Water plants properly.

Plants that are well-hydrated are less prone to winter burn. In particular, newly planted or young evergreens, especially those planted in open, exposed sites, those planted under eaves, or those planted in dry falls may suffer severe moisture loss during the winter and consequently severe winter burn. Established evergreens should receive approximately one inch of water per week and newly transplanted evergreens up to two inches of water per week during the growing season up until the soil freezes in the autumn or there is a significant snowfall. If supplemental watering is needed, use a soaker or drip hose to apply water near the drip lines of plants rather than using a sprinkler.

Avoid late summer or fall fertilization.

Applying quick-release, high-nitrogen fertilizers in late summer or fall could potentially stimulate growth of new foliage (particularly on some non-native evergreens) as well as inhibit proper onset of dormancy which can lead to damage over the winter. If you are concerned that your evergreens may need to be fertilized, submit a soil sample from around your plants to a professional soil testing lab that can provide specific information on what fertilizer to use and when to fertilize.

Protect plants during the winter.

Use burlap, canvas, snow fencing or other protective materials to create barriers that will protect plants from winter winds and sun. Install four to five foot tall stakes approximately two feet from the drip lines of plants especially on the south and west sides (or any side exposed to wind) and wrap protective materials around the stakes to create “fenced” barriers. Leave the top open. These barriers will deflect the wind and protect plants from direct exposure to the sun. Remove the barrier material promptly in spring. DO NOT tightly wrap individual plants with burlap as this can collect ice, trap moisture and make plants more susceptible to infection by disease-causing organisms. Use of anti-transpirant products to prevent water loss from foliage over the winter has been shown to have limited benefit. These materials degrade rapidly, require reapplication after each significant rain or snow event, and may not be effective in preventing water loss that can lead to winter burn.

For more information on winter burn:

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 Linda Chalker – Scott, Bert Cregg and Jean Ferdinandsen 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.wisc.edu.

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

Disease - Fruit Crop, Disease - Needled Woody Ornamental

White Pine Blister Rust

August 19, 2015 hudelson

UW Plant Disease Facts

Authors: Joseph Schwartz, UW-Madison Forest Ecology and Management and Glen R. Stanosz, Ph. D., UW Madison Plant Pathology

Last Revised: 03/02/2024

D-number: D0126

What is white pine blister rust?

White pine blister rust is a serious, tree-killing disease of eastern white pine and its close relatives (pines with needles in bundles of five). This disease is caused by the exotic (non-native) fungus Cronartium ribicola, which was introduced into North America in the early 1900’s. This pathogen is now found in most regions where pines grow in the United States, including Wisconsin. White pine blister rust affects trees of all ages, but perhaps most frequently and severely damages seedlings and saplings.

White pine blister rust cankers on branches and stems often have a cracked or blistered appearance and may bear yellow to orange spores in fruiting bodies of Cronartium ribicola.

Where does white pine blister rust come from?

White pine blister rust is caused by the fungus Cronartium ribicola, which requires two different plant hosts to complete its complex life cycle. Spores of the fungus produced on white pine are blown to alternate host plants in the genus Ribes (gooseberries and currants). After infecting gooseberry and currant bushes the fungus multiplies rapidly throughout the summer, repeatedly producing spores that germinate to result in additional gooseberry and currant infections. Spores produced in late summer on gooseberries and currants are spread by the wind to white pines, where needles that are moist from rain, fog, or dew are infected.

What does white pine blister rust look like?

Infection of needles by Cronartium ribicola results in development of yellow to brown spots and bands. The fungus slowly grows through pine needles and bark to eventually form cankers on twigs, branches, and trunks of trees. A canker is a localized diseased area (either swollen or sunken) that is surrounded by healthy tissues. A typical white pine blister rust canker has resinous margins, and may appear “blistered” before rupturing to expose fruiting bodies (reproductive structures) with yellow to bright orange spores of Cronartium ribicola. As a canker expands to completely encircle stems, all parts of the plant beyond the canker are killed. Dead white pine branches may temporarily retain their orange to red dead needles to form a bright “flag” that is a common symptom of this disease.

Can I save a tree affected by white pine blister rust?

There is no “cure” for a tree with a white pine blister rust canker on its main trunk or stem. As the canker expands to completely encircle the trunk, all parts above the canker will die. Branch cankers that extend to within four inches of the trunk, probably indicate that the trunk already is colonized by the fungus and future development of a main stem canker is likely. Pruning off branches on which cankers are located farther from the trunk, however, can prevent the fungus from growing into the trunk. These branch cankers can be removed by pruning at least six inches beyond any visible symptoms on the trunk side of the cankered branch. Removal of branch cankers and trees with main stem cankers prevents production of spores that are spread to gooseberries and currants. The fungus quickly dies in discarded branches and trunks and presents no further danger to either of its hosts.

How do I avoid future problems from white pine blister rust?

Infection of pine is most frequent near diseased gooseberries or currants. Therefore, removing these plants (especially within 200 feet) can greatly reduce the incidence of white pine blister rust. Gooseberries or currants can be killed by uprooting them or by application of herbicides in accordance with label directions.

Conditions that promote or prolong needle wetness should be avoided. These include use of sprinklers that wet the needles of ornamental trees, dense plantings, growth of weeds surrounding young trees, or planting white pines in low-lying, chronically moist areas near water or sites that lack good air movement. Growing white pines under a hardwood overstory that will intercept evening dew can help keep needles dry and reduce infection.

Regular inspection allows prompt detection and removal of cankered branches on young trees. Also, because infection very often occurs on needles of low branches, pruning to remove healthy branches (if aesthetically acceptable) will reduce the likelihood of this disease. When trees are five to seven years old, starting close to the ground, prune off all branches up to no more than one-third to one-half the height of the tree. Branch pruning can be continued every other year until the lower eight to nine feet of trunk is free of branches.

Planting or measures to encourage natural regeneration of conifer species other than white pines (including red or jack pines, spruces, firs, arborvitae, hemlock, and junipers) might be considered, especially where gooseberries or currants are prevalent and where moisture conditions favor infection.

Application of protectant fungicides may be a useful management practice in white pine production nurseries. Nursery stock should be carefully inspected, particularly just prior to sale, because the planting of diseased white pine seedlings is one way Cronartium ribicola has been spread into previously disease-free locations.

For more information on white pine blister rust:

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 Ann Joy and Brian Hudelson 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.wisc.edu.

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

Disease - Herbaceous Ornamental, Disease - Vegetable

White Mold

August 19, 2015 hudelson

UW Plant Disease Facts

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

Last Revised: 03/02/2024

D-number: D0125

Stem cankers, cottony mycelia and sclerotia (see arrows) of white mold on snap beans.

What is white mold?

White mold, also known as Sclerotinia stem rot, is a serious and typically lethal fungal disease that affects over 400 species of plants in many plant families. White mold causes severe damage in commercially grown snap beans, kidney beans, lima beans and soybeans (see UW Plant Disease Facts D0099, Sclerotinia Stem Rot), as well as commercially grown sunflowers. White mold also can be a serious problem in home vegetable gardens on tomatoes, potatoes, cucurbits (e.g., cucumber, pumpkin and squash), carrots, lettuce, celery, brassicas (e.g., cabbage, broccoli, and cauliflower), basil, and rosemary. White mold is a common disease on many annual and perennial ornamentals as well.

What does white mold look like?

Symptoms of white mold vary depending on the plant infected. White mold can lead to crown and stem cankers (i.e., localized infected areas), root rots, wilts, damping-off of seedlings, and blossom and fruit rots. Plants affected by white mold can wilt rapidly due to stem-girdling cankers at or near the soil line. Brown spots can appear on flower petals and buds. Cottony masses of fungal threads (called mycelia) may appear on stems or on nearby soil. Hard, irregularly-shaped masses (called sclerotia) develop within or on the surface of infected plants. The sclerotia are white at first and then turn dark brown or black as they mature, resembling mouse or rat droppings.

Where does white mold come from?

White mold is caused by several species of the fungus Sclerotinia, most commonly Sclerotinia sclerotiorum. White mold fungi overwinter as sclerotia in dead plant material or in infested soil. Sclerotia can survive in soil for at least five years. During periods of cool, wet or humid weather, sclerotia germinate to form either fungal threads (called hyphae) or tiny, mushroom-like spore-producing structures (called apothecia). Apothecia can release millions of spores over a period of several days. Spores are dispersed primarily by wind, but also by rainsplash and insects. Both spores and hyphae can infect plant tissue, with infection often occurring through dead or declining plant parts (e.g., flowers, leaves), and then spreading to healthy tissue. Infections may also occur through healthy plant parts that are growing near or in contact with the soil. In some plants, seeds can be contaminated by sclerotia or mycelia of white mold fungi.

White mold can be destructive on ornamentals such as Liatris.

How do I save plants with white mold?

White mold is difficult to manage once infections have occurred. Prune four to five inches below obviously disease tissue or remove entire plants if they are severely affected. DO NOT compost these materials because of the risk of spreading white mold fungi via long-lived sclerotia. Burn these materials instead.

How do I avoid problems with white mold in the future?

Check seed for sclerotia and remove these structures if you find them. Make sure your soils are well-drained, and avoid overwatering as well as frequent, light watering. DO NOT overhead water (e.g., with a sprinkler). Instead water deeply early in the day with a drip or soaker hose. Promote good air circulation in your garden so that plants more rapidly dry when they do get wet (e.g., from natural rain). Better air circulation can be achieved by choosing cultivars or varieties of plants that have a more open growth form, by spacing plants farther apart, by avoiding excessive use of nitrogen fertilizers (which can promote excessive production of lush, thick foliage), and by keeping weeds under control. Weed control also eliminates potential alternate hosts that white mold fungi can infect. As leaves and flowers or your plants naturally wither and die, remove them, as well as any other plant debris that may harbor white mold fungi. Finally, in beds where severe cases of white mold have occurred, consider removing and replacing infested soil.

For more information on white mold:

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 R. Vaughan James, Karen Delahaut & 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.wisc.edu.

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

Disease - Needled Woody Ornamental, Pest Alerts

Weir’s Cushion Rust of Spruces – Pest Alert

August 19, 2015 hudelson

UW Plant Disease Facts

Pest Alert

Authors: Glen R. Stanosz, UW Madison Plant Pathology, and Forest Ecology and Management

Last Revised: 03/02/2024

D-number: D0124

What is Weir’s cushion rust?

Weir’s cushion rust is a needle disease that disfigures and reduces growth of spruce trees (Picea spp.) of all ages. This disease has been known in both eastern and western regions of the United States, but was recognized in Wisconsin for the first time in 2002.

Yellow spots and bands in winter on spruce shoots affected by Weir's cushion rust. — Yellow spots and bands in winter on spruce shoots affected by Weir’s cushion rust.

What does Weir’s cushion rust look like?

Needles on current year’s shoots affected by Weir’s cushion rust may develop yellow spots or bands in the summer and fall. These spots and bands may intensify to give needles a bright “green and gold” appearance the following spring, when tiny blister-like pustules (a type of fungal reproductive structure) develop in the yellow areas. Microscopic examination of these pustules is required for diagnosis of the disease. Affected one-year-old needles continue to yellow, turn brown, and fall off as the spring and summer progress. Trees badly damaged by Weir’s cushion rust will have thin crowns due to repeated loss of the previous year’s needles.

Where does Weir’s cushion rust come from?

Weir’s cushion rust results from colonization of spruce needles by the fungus Ceropsora weirii (formerly Chrysomyxa weirii). This fungus overwinters in needles infected during the previous growing season. In late summer, or more typically the following spring, C. weirii produces spores in the pustules that develop on the needles. These spores can be blown by wind or splashed by rain to newly emerging needles on the same tree or other trees. Spore germination is followed by infection of young needles.

Can I save a tree affected by Weir’s cushion rust?

Apply fungicides containing chlorothalonil to trees affected by Weir’s cushion rust to prevent new needle infections. Make the first application when 10% of the buds have broken and two additional applications at seven to 10 day intervals thereafter. Fungicide applications do not kill the fungus in needles that are already infected, so be sure to begin applications promptly and complete the spray program, to ensure thorough coverage and protection of new foliage. Please be sure to read and follow all fungicide label instructions to ensure that you use the product in the safest and most effective manner possible. Needles infected by C. weirii eventually die. The fungus does not continue to live or produce spores on these dead needles. Therefore, destruction of dead needles is not necessary.

How do I avoid Weir’s cushion rust in the future?

DO NOT accept and plant landscape or nursery stock affected by Weir’s cushion rust. Inspect established spruce trees (in both landscape and nursery settings) in late summer and fall for evidence of Weir’s cushion rust (e.g., yellow spots and bands on the current year’s needles). Inspect suspect trees again in spring for these symptoms, as well as pustules of C. weirii on the previous year’s needles. In nurseries, move affected trees to areas where the disease is not already present. Use fungicide applications to prevent establishment of the fungus on new trees or in previously unaffected nurseries and landscapes.

For more information on Weir’s cushion rust:

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 Brian Hudelson 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.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 - Herbaceous Ornamental

Volutella Blight

August 19, 2015 hudelson

UW Plant Disease Facts

Authors: Gina Muscato and Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 03/02/2024

D-number: D0123

What is Volutella blight?

Volutella blight is a common and potentially lethal disease of Japanese pachysandra (Pachysandra terminalis), an evergreen, semi-woody groundcover that is grown in shade gardens throughout hardiness zones 4 and 5 in Wisconsin. Volutella blight can severely limit the aesthetic appeal of pachysandra wherever it is grown.

Volutella blight often starts as lesions on individual leaves, but can eventually kill groups of pachysandra plants.

What does Volutella blight look like?

Volutella blight begins as discrete, water-soaked areas (lesions) on pachysandra leaves and stems that eventually turn black/brown and become necrotic (i.e., die). Lesions can be circular, oval or irregular in shape, and may have darker margins. Distinct concentric rings also may be visible in the lesions. Lesions on a single leaf can merge and cause the collapse of the entire leaf, while stem lesions can lead to the collapse of an entire pachysandra plant. When severe, Volutella blight can kill large patches of a pachysandra planting.

Where does Volutella blight come from?

Volutella blight is caused by the fungus Volutella pachysandricola which survives in infected plants, as well as on and in pachysandra plant debris. During wet weather, this fungus produces masses of light-orange to pink fungal spores and hyphae (i.e., fungal threads) that may be visible to the naked eye.

How do I save a plant with Volutella blight?

Remove diseased leaves, as well as any leaf debris, and prune back or dig up plants with stem infections. Dispose of this material by burning (where allowed by local ordinance), burying or hot composting it. Be sure to prune only when plants are dry to minimize the spread of the causal fungus. Be sure to clean your pruning tools between cuts by treating them for at least 30 seconds in a 10% bleach solution or (preferably due its less corrosive properties) 70% alcohol (e.g., rubbing alcohol, certain spray disinfectants). If you use bleach, be sure to thoroughly rinse and oil tools after you are done pruning to prevent rusting.

When disease is severe, follow leaf and plant removal by treating remaining plants with one or more applications of a broad-spectrum fungicide (e.g., one containing chlorothalonil). Select a product that is labeled for use on pachysandra, and follow all label instructions to ensure that you apply the product in the safest and most effective way possible.

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

V. pachysandricola is a somewhat opportunistic pathogen, most often causing problems on pachysandra that is weakened or under stress. Therefore, reduce any stresses where possible. Reduce stress due to overexposure to sun by always planting pachysandra in a shady area. DO NOT overcrowd new plantings, and thin existing beds to not only reduce stress from competition but also to promote good air flow and rapid drying of plants. Dry plants are less likely to become infected than plants that stay wet for extended periods. To prevent water stress during the summer and reduce winter injury over the winter, established pachysandra should receive approximately one inch of water per week during the growing season up until the point where there is snowfall or the ground freezes. Newly planted pachysandra should receive approximately two inches of water per week. If there is insufficient rain, water plants using a soaker or drip hose. Minimize salt usage on sidewalks or driveways near pachysandra beds to limit salt injury that can predispose plants to infection. Control insect pests and avoid over-pruning of pachysandra to limit wounds that might serve as entry points for V. pachysandricola.

For more information on Volutella 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

Thanks to Diana Alfuth, Laura Jull and Christine Regester 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.wisc.edu.

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

Disease - Vegetable

Verticillium Wilt of Vegetables

August 19, 2015 hudelson

UW Plant Disease Facts

Authors: Ken Frost* and Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 03/02/2024

D-number: D0122

What is Verticillium wilt?

Verticillium wilt is a typically fatal disease that affects a wide range of vegetable crops in Wisconsin. Vegetables commonly and severely affected by Verticillium wilt include tomato, potato, pepper, eggplant, cucumber, muskmelon, pumpkin and watermelon. Other vegetables such as asparagus, bean, beet, broccoli, Brussels sprouts, cabbage, cauliflower, celery, chive, collards, garlic, kale, kohlrabi, leek, lettuce, mustard, onion, parsley, peas, radish, rutabaga, spinach and turnip are susceptible to Verticillium wilt, but show less severe symptoms. Some vegetables, such as sweet corn are immune to the disease. Many woody and herbaceous ornamentals are also susceptible to Verticillium wilt (see also UW Plant Disease Facts D0121 Verticillium Wilt of Trees and Shrubs).

A blotchy yellow leaf color can be an initial symptom of Verticillium wilt on eggplant. (photo courtesy of Amanda Gevens)

What does Verticillium wilt look like?

Initial symptoms of Verticillium wilt include sudden yellowing of foliage, typically first appearing on one side of a plant. These leaves then wilt and die. Oftentimes, symptoms mimic the natural aging process of leaves. Eventually however, the entire plant becomes affected and dies. By peeling away the outer layers of affected branches or vines, you may observe brown streaking in the vascular (water-conducting) tissue. Vascular browning is common in tomato and potato plants.

Where does Verticillium wilt come from?

Verticillium wilt is caused primarily by two fungi, Verticillium dahliae and Verticillium albo-atrum. These fungi are commonly found in Wisconsin soils. V. dahliae and V. albo-atrum have wide host ranges including many common weeds, such as ragweed, cocklebur, and velvetleaf. Susceptible plants and their debris can serve as an overwintering site for these fungi. In potato, root lesion nematodes (Pratylenchus spp.) can contribute to the development of Verticillium wilt. However, the role of these nematodes in Verticillium wilt development in other vegetable crops is not well understood.

How do I save a plant with Verticillium wilt?

Vegetables infected with Verticillium cannot be cured and will eventually die. However, you can extend the life of infected plants by fertilizing and watering them properly. Fertilization should be based on a soil nutrient test and should be tailored to the specific vegetables being grown. Most vegetables require approximately one inch of water per week. If natural rains are not sufficient, then supplemental water should be applied using a soaker or drip hose.

Verticillium wilt eventually leads to wilting and plant death. (photo courtesy of Amanda Gevens)

How do I avoid problems with Verticillium wilt in the future?

Do not repeatedly grow crops that are highly susceptible to Verticillium wilt in the same area of your garden each year. Try to rotate highly susceptible crops with other less susceptible crops. See University of Wisconsin Garden Facts XHT1210, Using Crop Rotation in the Home Vegetable Garden, for details on this process. Also, try to plant vegetable varieties that are resistant to Verticillium wilt. In particular, many modern tomato varieties are resistant to the disease. Watch for varieties with the letter “V” after the variety name. If Verticillium wilt resistant varieties of your favorite vegetables are not available, select varieties that mature early. Early maturing varieties are more likely to produce usable vegetables before they eventually succumb to the disease than late maturing varieties.

In addition to using resistant varieties, try to eliminate sources of Verticillium in your garden. Keep broadleaf weeds under control, as these plants are often susceptible to Verticillium wilt and can serve as a reservoir for the fungus. DO NOT use mulches that may have been produced from trees (e.g., maple and ash trees) that are susceptible to Verticillium wilt, and immediately collect and discard leaves that have fallen from symptomatic trees. Also, remove and discard debris from susceptible vegetable plants. Burn (where allowed by local ordinance) or landfill infected plants and infested plant debris. DO NOT bury or compost these materials. Finally, decontaminate any gardening items (e.g., shovels, hoes, plant stakes, pots, working surfaces, etc.) that may have come into contact with Verticillium to prevent spread of the fungus. Rinse these items with water to remove clinging soil, then treat them for at least 30 seconds with a 10% bleach solution or (preferable for metal tools due its less corrosive properties) 70% alcohol (e.g., rubbing alcohol, certain spray disinfectants). If you use bleach, be sure to thoroughly rinse and oil metal tools after gardening to prevent rusting.

For more information on Verticillium wilt:

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 Plant Pathology 875 – Plant Disease Diagnostics Clinic Internship at the University of Wisconsin Madison.

Thanks to Rosemarie Bugs, Amanda Gevens and Chris Parise 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.wisc.edu.

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