Category Archives: Misc

Cucumber Mosaic

What is cucumber mosaic?  Cucumber mosaic is a viral disease of worldwide distribution that affects over 1200 plant species.  Hosts include a wide range of fruits, vegetables, herbaceous and woody ornamentals, and weeds.  The disease has perhaps its biggest impact in vegetable production where it can cause significant losses in yield and vegetable quality.

Cumber mosaic on pepper (left) showing yellowing and ring spots, and on broad bean (right) showing mosaic and puckering of leaf tissue. (Photos courtesy of Russ Groves)
Cumber mosaic on pepper (left) showing yellowing and ring spots, and on broad bean (right) showing mosaic and puckering of leaf tissue. (Photos courtesy of Russ Groves)

What does cucumber mosaic look like?  Symptoms of cucumber mosaic can vary widely depending on host species, host variety, and time of infection.  Typical symptoms include stunting of entire plants, mosaic or mottling (i.e., blotchy white, yellow, and light green areas) and ring spots (i.e., ring-like areas of discolored tissue) on leaves and fruits, and a variety of growth distortions such as cupping, puckering and strapping (i.e., elongation and thinning) of leaves as well as warts on fruits.  In extreme situations, parts of an affected plant or even an entire plant may die from the disease.

Where does cucumber mosaic come from?  Cucumber mosaic is caused by Cucumber mosaic virus (CMV) which can overwinter in susceptible biennial or perennial weeds, as well as in perennial agricultural crops (e.g., alfalfa) and perennial herbaceous and woody ornamentals.  Seeds and even pollen from certain host plants can carry the virus, and thus the virus can be spread via these plant parts.  More commonly, CMV is spread by aphids [see the University of Wisconsin Garden Facts XHT1043 (“Aphids”) for details on these insect pests] which can pick up the virus from infected plants and transmit it to healthy plants as they feed.  Over 80 species of aphids can potentially transmit CMV.  The severity of cucumber mosaic oftentimes depends on the size and activity of aphid populations in an area, as well as on the number infected plants in an area serving as reservoirs for the virus.

How do I save plants with cucumber mosaic?  There is no known cure for cucumber mosaic.  Infected plants should be removed and destroyed to eliminate the plants as potential reservoirs for the virus (which can subsequently be spread to other nearby healthy plants).  Infected plants can be burned (where allowed by local ordinance), deep buried or hot composted.  Killing infected plants with herbicides can also be an effective management strategy.

Cumber mosaic on hibiscus (left) showing mosaic and puckered leaves, and on bluebell (right) showing mosaic and line patterns. (Photos courtesy of Brian Hudelson)
Cumber mosaic on hibiscus (left) showing mosaic and puckered leaves, and on bluebell (right) showing mosaic and line patterns. (Photos courtesy of Brian Hudelson)

How do I avoid problems with cucumber mosaic in the future?  Buy certified, virus-free seeds and plants.  Consider using CMV-resistant varieties of lettuce, spinach, cucurbits (e.g., cucumber, melon and squash) and other vegetables where available.  Seed catalogs often contain information on CMV resistance that can be useful for variety selection.  Remove weed hosts whenever possible around your garden and mulch vegetable and ornamental gardens to inhibit weed growth.  Consider using floating row covers where possible to prevent aphids from reaching susceptible plants.  DO NOT use insecticides to control aphids because such treatments are unlikely to act fast enough to prevent aphids from transmitting CMV, and may actually stimulate aphids to move and feed more widely, thus leading to increased spread of the virus.

For more information on cucumber mosaic:  Contact your county Extension agent.


What are stinkhorns?  Stinkhorns are mushrooms that are found from the tropics to more temperate regions such as Wisconsin.  They can suddenly appear in mulch, lawns, and areas with bare soil.  These visually-shocking fungi get their common name from their characteristic, unpleasant odor.  Although they are often unwanted additions to home gardens, stinkhorns do not cause plant disease.  Because stinkhorns can grow on dead organic material, they actually are beneficial in that they contribute to the recycling of plant debris into nutrients that improve soil fertility and can be used by garden plants.

Stinkhorns come in many shapes and sizes. They produce foul odors and slimes that attract flies. [Photos (clockwise from the upper left) courtesy of Tom Volk (, Ted Geibel, Troy Bartlett and Gloria Schoenholtz]
Stinkhorns Photo 2
In their immature “egg” stage, stinkhorns can be found below ground. Cutting the “eggs” in half, reveals the developing stinkhorn mushroom. [Photo courtesy of Tom Volk (
What do stinkhorns look like?  Stinkhorns grow into various shapes, but they are best known for looking like horns or penises.  A few species grow several appendages, resulting in an octopus-like appearance.  Some species have a veil attached below the cap that resembles a lacey skirt flowing from the mushroom’s hollow stalk.  Stinkhorns can range in color from white, beige, and olive to bright orange or red with black accents.  The tips of mature stinkhorns are usually coated in a spore-containing slime.  Gardeners often discover immature stinkhorns as they dig in the soil.  The immature forms appear as whitish to pink or purple, egg-shaped masses.  Stinkhorns develop rapidly sometimes growing up to four to six inches per hour, and can generate enough force to break through asphalt.

Where do stinkhorns come from?  Stinkhorns are often first introduced into a garden in organic materials (e.g., soils and mulches) that contain microscopic hyphae (i.e., fungal threads) of stinkhorn fungi.  Once stinkhorns mature, they produce a pungent, off-putting odor that is reminiscent of rotting flesh or dung.  This smell may disgust people, but it attracts insects, particularly flies.  Flies and other insects eat the slimy material at the tips of stinkhorns and carry spores in this slime to new locations as they move around in the environment.  In many ways, this process is comparable to the distribution of pollen by bees (but of course without the more appealing scents associated with most flowers).

How do I control stinkhorns?  Stinkhorns are short-lived and will naturally disappear quite rapidly.  If stinkhorns are too unsightly, if their smell becomes too putrid, if they attract too many insects, or if there is concern about small children or pets eating them, pluck them from the ground and discard them as they appear.  Keep in mind however, that removing stinkhorns will not eradicate them.  Stinkhorn hyphae will remain in the soil or mulch and will eventually produce other stinkhorn mushrooms.  In addition, flies and other insects carrying stinkhorn spores can introduce these fungi to new locations.

How can I prevent problems with stinkhorns in the future?  No fungicide treatments or other methods are available to prevent stinkhorns from appearing in a garden.  Removing organic matter (e.g., mulch) or reducing soil moisture may reduce the number of stinkhorns that appear.  However, these strategies are unlikely to eradicate stinkhorn fungi.  Therefore whenever stinkhorns appear, consider embracing their unique beauty and enjoy their brief time in your garden.

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


Slugs are legless, soft-bodied creatures that resemble snails without a shell. Slugs feed on a wide range of plants including ornamentals, vegetables and fruits. A number of species of slugs are found in Wisconsin, but gray and spotted garden slugs are the most common, and the most likely to cause damage.

A slug.
A slug.

Slugs overwinter either as adults or as eggs, and develop slowly, often living for more than one year. They are often found in higher numbers in areas where sod or other plant residues have been tilled under during the previous growing season. Slugs become active during the first warm days of spring, and thrive under cool, damp conditions. Slug populations will be high during and following damp, rainy weather, and will almost disappear during dry periods. Slugs cannot survive direct sunlight, and without protective hiding places during the day, they rapidly lose body moisture and die. Rock walls, boards, pots and plant debris, as well as shaded flower beds and heavily mulched gardens, serve as ideal daytime resting sites.

Slugs damage plants by chewing large, irregular holes in leaves, stems, flowers or fruits. Most feeding occurs at night or during dark, cloudy days. A shiny trail of mucus (slime) may be associated with the damage. Vegetables and fruit in direct contact with the soil are attacked more frequently than those off the ground. In Wisconsin, tomatoes are often damaged just as they ripen.

Control: There are a number of cultural control options available for controlling slugs. These include:

  • removing plant debris, boards or other places where slugs might survive during the day;
  • strategically placing boards, carpet patches or inverted flower pots, and collecting and destroying slugs that congregate under these items;
  • watering in the morning so that gardens dry out before evening hours when slugs are most likely to be active;
  • raking mulch in the winter to expose slugs to adverse environmental conditions that are likely to lead to increased mortality;
  • placing copper strips around flowerpots or flowerbeds that will deter slugs from crawling onto plants;
  • using regular applications of an abrasive, sharp-edged material such as diatomaceous earth, gravel or sand to deter slug movement;
  • placing fresh, undiluted beer (heavy, yeasty varieties work best) in a container set flush with the ground to bait and drown slugs;
  • searching your garden at night with the aid of a flashlight and destroying any slugs that you find.
Slug damage on a Hosta leaf.
Slug damage on a Hosta leaf.

Slugs are often naturally controlled by the feeding of toads, frogs, birds, ground beetles and firefly larvae. In Europe, parasitic nematodes (Phasmarhabditis hermaphrodita) have been used for slug control. Unfortunately, these nematodes products are not commercially available in the US.

Slugs can also be controlled using chemical products. However, keep in mind that slugs are not insects, and will not respond in most cases to insecticides. There are however, a number of commercial products that contain iron phosphate or metaldehyde that can be used as baits for slug control. These products are sold as pellets, or can be packaged in plastic feeding stations. Baits are most often used in large scale agricultural settings when slug control is needed. If you decide to use a commercial bait for control, be sure to read and follow all label instructions of the product that you select to insure that you use the bait in the safest and most effective manner possible.

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

Slime Molds

What is a slime mold? Slime molds are members of a shape-shifting group of organisms called myxomycetes. These organisms are found all over the world, even in deserts, high altitudes, and on the edges of snowbanks. Although they often resemble fungi, slime molds are more closely related to amoebas and certain seaweeds.

A dog vomit slime mold is shown spreading across mulch and up the base of a shrub.
A dog vomit slime mold is shown spreading across mulch and up the base of a shrub.

What does a slime mold look like? A slime mold spends most of its life as a lumpy mass of protoplasm, called a plasmodium, that moves and eats like an amoeba. It may be white, yellow, orange, or red. The color of a particular species can vary slightly with temperature, pH, and the substances the plasmodium eats. One very common slime mold, Fuligo septica, looks like dog vomit or scrambled eggs, from which it derives its common names. Others resemble a network of veins or a fan. In the course of a few hours a slime mold can transform from its amoeba-like phase into its fungus-like phase, which produces spores.

Where do slime molds come from? The most common slime molds in Wisconsin love moist, shady places like crevices in rotting logs, leaf letter, and bark mulch. Spores of slime molds are resistant to adverse conditions and will germinate after a heavy rain. The plasmodium forms from many individual swimming cells called swarm cells. The plasmodium can move at a very slow rate, feeding on bacteria, other microorganisms, and organic matter. Changes in moisture or temperature, or exhaustion of its food supply can cause the slime mold to move to a drier, more exposed location to produce spores.

What do I do with a slime mold in my garden or lawn? Slime molds do not cause diseases of plants or turf. They do use leaves and stems as surfaces on which to grow and can block out sunlight leading to leaf-yellowing. The best way to get rid of a slime mold is to break it up and dry it out. Rake up and dispose of slime molds on bark mulch. For slime molds on turf, mow the lawn, and rake up the thatch. Alternatively, you may want to enjoy a slime mold if you find one in your yard. These complex organisms are fascinating to observe with a hand lens and can be “captured” and grown indoors as a science project.

For more information on slime molds: Visit Tom Volk’s website at, or contact your county Extension agent:


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

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

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

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

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

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

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

Black Walnut Toxicity

What is black walnut toxicity? Black walnut trees (Juglans nigra) produce a toxic substance (called juglone) that prevents many plants from growing under or near them. Related trees like butternut (J. cinerea) and shagbark hickory (Carya ovata) also produce juglone, but in lower concentrations than black walnut. Juglone occurs in all parts of black walnut trees, but especially in buds, nut hulls and roots. The toxic effects of a mature black walnut tree can extend 50 to 80 feet from the trunk of the tree, with the greatest toxicity occurring within the tree’s dripline. In this area, plants susceptible to juglone may wilt or die; plants tolerant to juglone will grow normally. Vegetables such as tomato, potato, eggplant and pepper, and ornamentals such as lilac, peony, rhododendron and azalea are particularly sensitive to juglone. What do the effects of black walnut toxicity look like? Plants sensitive to juglone may be stunted, have yellow or brown, twisted leaves, exhibit wilting of some or all plant parts, and die over time. Often, the vascular (i.e., water-conducting) tissue of affected plants will be discolored. Symptoms may occur rapidly, even within a few days after sensitive species are transplanted into a walnut tree’s root zone. Alternatively, some plants may survive for years near a young walnut tree, but will wilt and die as the tree increases in size. Black walnut toxicity can be confused with wilts caused by bacterial and fungal pathogens (e.g., see University of Wisconsin Garden Facts X1008), herbicide injury (see University of Wisconsin Garden Facts X1004), or drought. How do I avoid problems with black walnut toxicity? There is no cure for a plant affected by walnut toxicity. Removing a walnut tree may not be practical as the tree could be the focal point in a landscape. In addition, even if a walnut tree is removed, juglones will not immediately be eliminated, because it is next to impossible to remove all root pieces from the soil and remaining pieces may continue to exude toxins for several years as they decay. When establishing a garden around a walnut tree, try to plant species that are tolerant to juglone (see table on the reverse side). If you are growing sensitive species near a walnut tree, transplant them elsewhere in your garden. If you must grow sensitive plants near a black walnut, keep beds free of walnut leaves and hulls and remove walnut seedlings as they appear. Growing shallow rooted woody and herbaceous plants, and improving drainage can also diminish the effects of juglone. Alternatively, consider building raised beds with wood, stone, or concrete barriers that limit root growth through and under the beds. When disposing of bark and wood from a walnut tree, do not use these materials for mulch. The information in the following table is intended to provide guidance in selecting plants to grow near walnut trees. Inclusion of plants in this table is based on observation, not on formal testing. In addition, the plant lists in this table are by no means exhaustive. Oftentimes the juglone sensitivity or tolerance of specific plants has never been observed or documented. Finally, sources often disagree on whether particular plants (e.g., columbine, lily, narcissus, tulip) are juglone sensitive or tolerant. Some varieties may be susceptible while others are tolerant. Most plant species with conflicting information regarding their sensitivity or tolerance to juglone have not been included in the table.


Sensitive to Juglone

Tolerant of Juglone
Vegetables asparagus, cabbage, eggplant, pepper, potato, rhubarb, tomato beans, beet, carrot, corn, melon, onion, parsnip, squash
Flowers autumn crocus, chrysanthemum, forget-me-not, petunia, peonies aster, astilbe, bee balm, begonia, black-eyed Susan, bluebell, calendula, crocus, daylily, ferns, grape hyacinth, some hosta varieties, hollyhock, impatiens, Jack-in-the-pulpit, Jacob’s ladder, marigold, morning glory, pansy, phlox, Siberian iris, squill, sweet woodruff, trillium, zinnia
Trees alder, apple and crabapple, basswood, pine, spruce, silver maple, white birch black locust, catalpa, Eastern redbud, hackberry, Canadian hemlock, hickory, most maples, oaks, pagoda dogwood, poplar, red cedar
Shrubs and Vines azalea, blackberry (and most berries other than black raspberry), cotoneaster, hydrangea, lilac, mountain laurel, potentilla, privet, rhododendron, yew arborvitae, bittersweet, black raspberry, clematis, currant, forsythia, euonymus, greenbrier, most honeysuckle, pachysandra, rose-of-Sharon, sumac, most viburnum, Virginia creeper, wild grape, wild rose, willow, witch hazel
Field Crops and Grasses alfalfa, tobacco fescue, Kentucky bluegrass, orchard grass, soybean, timothy, wheat, white clover

For more information on black walnut toxicity: See UW-Extension Publication A3182 or contact your County Extension agent.

Bird’s Nest Fungi

What are bird’s nest fungi? Bird’s nest fungi are a group of organisms named for their resemblance to miniature bird’s nests. These fungi are found all over the world, growing and reproducing on decomposing organic matter. In temperate regions, bird’s nest fungi can be found virtually anytime there are damp, shady conditions, but they are most commonly seen in the autumn.

Fruiting bodies of Crucibulum laeve found on decaying wood.  (Photo courtesy of Mark Steinmetz)
Fruiting bodies of Crucibulum laeve found on decaying wood. (Photo courtesy of Mark Steinmetz)

What do bird’s nest fungi look like? Bird’s nest fungi are best identified by the appearance of a brown, gray, or white outer “nest”, with brown or white “eggs” inside. The “eggs” are actually spore-containing structures called peridioles that rest inside the cup-shaped fruiting body (reproductive structure). Individual fruiting bodies are usually only ¼ to ½ inch in diameter and vary in shape, size, and color depending upon species.

Where do bird’s nest fungi come from? Bird’s nest fungi are classified in the fungal group gasteromycetes. Cyathus spp., Nidula spp., Crucibulum spp., Nidularia spp., and Mycocalia spp. are the most common genera of bird’s nest fungi. These fungi are often found in moist, shaded areas, and typically survive on soil, plant remains, decaying wood, or horse and cow excrement. The characteristic “cup and egg” structure of the bird’s nest fungi provides a unique method of dispersing spores. In a storm, the “eggs” are splashed out of the “cups” by raindrops. “Eggs” can travel a meter or more before sticking to another object. When the “egg” dries, it splits open releasing fungal spores.

What do I do with bird’s nest fungi in my yard? Bird’s nest fungi are not harmful to living plants and control of these fungi is typically not necessary. In fact, bird’s nest fungi can be fascinating organisms to observe when you find them in your yard. On occasion, bird’s nest fungi can be a nuisance, particularly when the “eggs” stick to objects such as houses or cars where they are difficult to remove. If bird’s nest fungi become a nuisance, the number of fruiting bodies can be reduced by decreasing irrigation and raking the affected area. The use of non-mulch groundcovers, such as ivy, can also reduce the occurrence of these fungi. Fungicides are not recommended for treatment of bird’s nest fungi.

For more information on bird’s nest fungi: Contact your county Extension agent.