All posts by ddlang

April 2021: Tomato in the Basement, Canary in the Coalmine

Canary IconI have the coolest job on the planet.  Everyday, I get to help people with their plant disease problems.  This may entail helping someone learn how to grow healthy, nutritious vegetables to feed their family or assisting a grieving family select the just the right tree to plant to serve as a lasting memorial for a recently lost loved one.  On occasion, I get to help Wisconsin farmers avoid severe economic losses due to plant diseases or help prevent the introduction of federally regulated plant pathogens that potentially can have negative impacts nationwide  This month, I’d like to share with you a diagnostic case where a proper diagnosis had the potential to save someone’s life.

I recently received photos from a home gardener who was growing tomato transplants indoors.  She was concerned that her plants were not doing well and losing leaves.  Her photos showed plants with leaves that were cupping downward and showed twisted petioles and other growth distortions.  I was immediately suspicious that the plants had been exposed to ethylene.  Ethylene is a gas that is a plant growth hormone that can be very beneficial for proper plant development; in particular, ethylene is important in fruit ripening.  But in other situations, when plants are exposed at the wrong time or at too high of a concentration, ethylene can have negative effects, in fact exactly the sort of symptoms I was seeing in my client’s photos:  distorted plant growth and premature leaf loss.

Tomatoes Damaged by Ethylene
Tomatoes suffering from ethylene exposure. Photo courtesy of Kristine Meixensperger.

After an exchange of several emails, the puzzle pieces started to fall into place.  My client had been growing her tomatoes in the basement (not uncommon for many gardeners) next to the boiler that provided heat for her home.  As the weather warmed up, she moved the plants to her garage where she parks her car and where she has a full kitchen.  She had been cooking in this kitchen recently to provide a bit of additional warmth for her plants.  Both her boiler and stove burn propane.

At this point, alarm bells were going off.  If propane burners malfunction and don’t burn propane completely, one of the breakdown products of this incomplete combustion is ethylene.  You can also find ethylene in exhaust fumes from motor vehicles, in the smoke produced by wood-burning stoves and as a contaminant in natural gas.  I suggested to my client that she should have her boiler and stove checked immediately for problems.  One or both of these (and possibly also fumes from her car) were likely the source of ethylene that was causing problems for her tomatoes.  She emailed back to tell me that what I had told her made perfect sense as her tomatoes nearer the boiler had more severe symptoms than those farther away.  Another sentence from this email became the inspiration for the title of this article:  “So the tomatoes plants in the basement acted like a canary in a coalmine.”

I told her that she was spot on with her analogy, and at that point, I gave potentially even more serious news.  In addition to producing ethylene, malfunctioning propane burners (and other types of heating systems) also can produce carbon monoxide, a potentially deadly gas.  According to the CDC, approximately 50,000 people visit hospitals with carbon monoxide poisoning each year and at least 430 of these people die from this poisoning.  Luckily, my client had a carbon monoxide detector near the boiler and it hadn’t gone off.  But, the unit was old, and my client indicated that our conversation had made her realize that she needed to replace that unit.

What if she hadn’t had a carbon monoxide detector?  Then, those distorted tomatoes would have been her first hint that a potentially deadly carbon monoxide situation was developing.  Similarly, if she had had distorted tomatoes growing near a natural gas-fueled furnace, that could have indicated a natural gas leak, another potentially lethal situation.

Ah, the power of a lowly vegetable and a bit of knowledge about how they grow!

For additional information on the PDDC and its activities, check out the PDDC website.  To learn about new PDDC education materials and programs, follow the clinic on Twitter or Facebook (@UWPDDC) or contact the clinic at pddc@wisc.edu and ask to be added to the PDDC’s listserv (UWPDDCLearn).

Beginning Vegetable Garden Basics: Site Selection and Soil Preparation

Starting a vegetable garden may seem overwhelming to a first-time gardener.  However, learning gardening basics and being successful in gardening endeavors can be quite easy.  This fact sheet focuses on how novice gardeners can select and prepare their garden site to ensure maximum success.

Careful site selection and planning can help you maximize your gardening success.
Careful site selection and planning can help you maximize your gardening success.

Where should I plant my garden?  Most vegetables require full sun (i.e., at least six hours of direct sunlight) each day.  Watch a potential garden site throughout the growing season to make sure that trees or buildings do not shade the area from late morning through the afternoon.  A garden area should be well drained; water should not puddle or significantly flow through the area during heavy rains.   Avoid low spots where frost might settle in late spring or early fall, and steep slopes where runoff or erosion could occur.  Be sure the area has a convenient water source (e.g., access to a hose) so that you can water during dry spells.  DO NOT locate a garden within the root zone of black walnut trees.  These trees produce chemicals (juglones) that interfere with the growth of many vegetables.  See University of Wisconsin Garden Facts XHT1017, Black Walnut Toxicity, for details.  Keep in mind that the roots of a tree can grow three to five times the height of a tree away from the trunk.  Finally, make sure there are no underground utility lines where you plan to garden.

How big should my garden be?  Plan the size of your garden based on what you want to grow.  Crops like beans, beets, herbs, lettuce, onions, potatoes, radishes, squash and tomatoes are good options for first-time gardeners.  Start small with just a few crops that are easy to grow and care for.  Research (e.g., online, in seed catalogs, etc.) how large your selected vegetables will grow, and plan enough garden space so that they are not crowded.  Proper spacing promotes good air circulation and sunlight exposure.  Crowded plants will be less productive, difficult to maintain, and more susceptible to diseases.  Consider using bush varieties of vining crops like squash as these take much less space than vining varieties.  Tomato plants should not touch each other when fully mature and should be trellised to prevent crowding.  Cucumbers and smaller-fruited squash can also be trellised to improve spacing.  Space vegetables like beans, carrots and radishes that are seeded in rows according to the instructions on their seed packets.

When planning your garden, consider drawing a map to scale using graph paper to be sure you have enough space for your plants.   See Extension bulletin A1989, The Vegetable Garden, available at https://learningstore.extension.wisc.edu, to learn more on garden mapping, as well as about space requirements for many common vegetables.

Adding compost can improve the structure and fertility of most garden soils.
Adding compost can improve the structure and fertility of most garden soils.

How do I prepare my garden soil?  Ideally, start preparing your garden site the year before planting.  Remove any existing vegetation from your garden site (particularly grass).  You do not want this to grow back in your garden later.  A sod cutter (available to rent in most locations) can be useful for removing grass.  Alternatively, if the garden area is small enough, you can remove grass by hand using a shovel.  Be sure to collect any excess soil from the dug sod and return it to your garden.  After removing whatever vegetation you can, cover the area with cardboard, a tarp or black plastic to smother out any remaining vegetation that you have not been able to remove.

Once your garden area has been cleared of vegetation, add compost to improve the overall soil structure.  Compost helps sandy soils hold more moisture and nutrients, and it makes clay soils lighter and better drained.  Compost also adds trace nutrients needed by plants.  Work a two to three inch layer of compost into the soil with a rototiller or shovel at least a month prior to planting.  Smooth the surface so that you are ready to plant when the weather is appropriate.

Also, consider having the soil in your garden nutrient tested through a certified lab before planting.  A soil test will provide information on the type of soil, the soil pH, the amount of organic matter, and the levels of phosphorous and potassium.  The optimal pH for a vegetable garden is around 6.5, although most vegetables will grow very well with a pH anywhere between 6.0 and 7.2.  A good soil-testing lab will also give you specific recommendations of what to add to your soil to adjust the pH and improve nutrient levels to grow vegetables more successfully.  If you do not have time to test the soil before planting, you can submit a sample later and still make amendments.  However, amending soil after planting is more challenging.

For more information on site selection and soil preparation for vegetable gardens:  Contact your county Extension agent.

Lily Leaf Beetle – Pest Alert

The lily leaf beetle (LLB), Lilioceris lilii, also known as the red or scarlet lily beetle, is an invasive insect of Eurasian origin.  This insect was first reported in North America in eastern Canada during World War II and was most likely introduced in shipments of plant materials from Europe.  LLB spread to New England in the 1990’s and has been moving westward since that time.  LLB made its first appearance in Wisconsin in 2014 and as of early 2021 has been found in 21 counties including Brown, Calumet, Clark, Dane, Door, Langlade, Lincoln, Marathon, Milwaukee, Oneida, Outagamie, Pierce, Portage, Price, Shawano, Taylor, Vernon, Vilas, Waukesha, Waupaca and Wood Counties.

Severe feeding damage from lily leaf beetles on a lily plant (left) and an adult lily leaf beetle (right). Photos courtesy of Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Severe feeding damage from lily leaf beetles on a lily plant (left) and an adult lily leaf beetle (right). Photos courtesy of Leslie J. Mehrhoff, University of Connecticut, Bugwood.org

LLB can cause significant damage to true lilies (Lilium spp.), including both native and cultivated types, as well as fritllaries (Fritillaria spp.).  LLB can also cause damage, but to a lesser extent, to lily of the valley (Convallaria majalis) and Solomon’s seal (Polygonatum spp.).  LLB does not cause damage to daylilies (Hemerocallis spp.), canna lilies (Canna spp.) or calla lilies (Calla palustris).

Appearance:  LLB adults are bright red and approximately 1/4 inch long, with black legs, head, antennae, and undersides.  When disturbed, LLBs tumble from plants and land upside down on the ground, where they play dead.  Their dark-colored undersides make them hard to spot.  To potentially deter predators, adults squeak if squeezed.

LLB larvae have plump, squishy bodies and are slug-like in appearance.  They tend to be orange or yellowish in color with black heads.  At maturity, larvae can be almost 1/2 inch long.  As a defensive tactic, larvae typically camouflage themselves with their own excrement and can resemble slimy greenish-brown slugs or a mobile pile of animal droppings.

LLB eggs are tiny (less than 1/10 inch long) and reddish in color.  Female LLBs lay the eggs (typically in a batch of a dozen or less) on the underside of leaves in a row parallel to a vein.

Symptoms and Effects:  Both LLB adults and larvae chew irregular holes and notches in lily leaves, stems, and developing buds.  Larvae are the more damaging stage of the insect.  When feeding damage is severe, LLBs can completely defoliate plants and destroy flowers.

Life Cycle:  There is a single generation of LLBs each year, but adults can live for several years.  LLBs overwinter as adults in sheltered places, soil, and plant debris in gardens and wooded areas.

These overwintering sites are not necessarily near lilies or other host plants.  Early in the spring, LLB adults emerge to feed, mate and lay eggs.  Because they are strong fliers, LLBs can disperse over long distances to locate host plants.  Eventually, females lay between 250 and 450 eggs.  Eggs hatch within four to eight days.  Emerging larvae feed for two to three weeks during the spring and early summer.  Engorged larvae eventually drop to the soil to pupate (i.e., transform into adults).  Pupae are bright orange and encased in a white cocoon with black spots.  Adults emerge 16 to 22 days later and feed throughout the rest of the growing season and into the fall.

Lily leaf beetle eggs (left) and a lily leaf beetle larva camouflaged with its own feces. Photos courtesy of Gail Hampshire (left) and Kenneth R. Law, USDA APHIS PPQ, Bugwood.org
Lily leaf beetle eggs (left) and a lily leaf beetle larva camouflaged with its own feces. Photos courtesy of Gail Hampshire (left) and Kenneth R. Law, USDA APHIS PPQ, Bugwood.org

Control:  If you have a small number of lilies, consider hand-picking and crushing adults and larvae or knocking them into a container of soapy water.  Also, crush eggs by hand if you see them.  Repeat this process regularly throughout the growing season.  If LLB becomes a chronic and severe problem, consider replacing your lilies with plants that are not attacked by the insect.

You can also use conventional and organic insecticides to help protect plants from the LLB.  Conventional insecticides containing carbaryl, cyfluthrin, cypermethrin, deltamethrin, lambda-cyhalothrin, permethrin, and zeta-cypermethrin control a broad range of pests, including LLB.  Organic insecticides containing azadirachtin, pyrethrins, or spinosad can also be used, as well as horticultural oils and insecticidal soap.  Make sure that the product that you select is labelled for use on landscape flowers.  Be aware that conventional and organic insecticides can pose risks to pollinators, so follow all directions on the label to minimize risks to bees and other pollinators.

For more information on lily leaf beetle:  Contact your county Extension agent.

April 2021: Water, Water, Everywhere, but Never, Ever on the Leaves

Thundercloud with RainApril conjures up visions of spring rain showers, eventually leading to May flowers.  While Mother Nature waters plants using an overhead sprinkling system (i.e., rain), from plant disease standpoint, this type of watering is less than optimal.

What’s the problem with watering from above?  Overhead watering wets leaves creating what plant pathologists call a “leaf wetness period,” a time when a thin layer of water coats the leaf.  This layer of water is exactly what most plant diseases-causing fungi require for their spores to germinate and infect.  The longer the leaf wetness period, the more likely leaf diseases will be a problem.

Wet Leaves - Photo by Diana Alfuth

What do I do to prevent watering issues?  You can’t prevent rain, but during dry periods when you need to water, don’t simulate rain by using a sprinkler.  Instead, use a soaker or drip hose that directs water into the soil rather than onto leaves.  Water at low pressure so that any sprays from these hoses are minimized.  When it does rain, promote rapid drying of leaves by spacing plants as far apart as possible in new plantings, and thinning existing beds to increase spacing.  Wider plant spacing increases air flow, promotes more rapid drying of leaves (when leaves do get wet), and shortens leaf wetness periods, making it more difficult for plant pathogens to get a foothold.  Don’t overwater either.  Excessive soil moisture eventually increases humidity around plants, which slows leaf drying and lengthens leaf wetness periods.

By taking just a little extra care in how you water, you can have a big impact on the health of the plants in your garden.

For more information on leaf diseases, check out the fact sheet section of the UW-Madison PDDC website (https://pddc.wisc.edu/fact-sheet-listing-all/).

Photo courtesy of Diana Alfuth.

March 2021: Gardening Ideas for the 2021 Growing Season

Plant Light BAs the temperatures begin to warm and the snow melts, gardeners are chomping at the bit to be outdoors working away.  Thoughts tend towards “What should I plant this year?” and “When should I plant and seed?”  Those are great questions, but there are other aspects of gardening that I think are important to consider.  This month, I’d like to share what I think about at this time of year as I try to prepare for a successful growing season.

Garden clean-up.  I often talk about the importance of fall clean-up for plant disease management.  Plant pathogens often overwinter in debris from infected plants left over from the previous growing season.  Removing this material from a garden helps eliminate a source of pathogens that can reinfect plants during the current growing season.  While fall is a great time to do this removal, there are a variety of reasons why gardeners might choose not to do clean-up in the fall.  Some people just don’t have the time.  Some like to use leaf litter to insulate flower beds.  Others like to maintain plants that have died back for winter visual interest in their gardens or as overwintering sites for beneficial insects.  If you’re one of the people who likes keep plant debris around for the winter, spring is the time to take care of this material.  Try to remove the debris before plants begin to produce new growth, and burn (where allowed), bury or hot compost it.

Watering concerns.  This can be a tough time of year for many evergreens (particularly yews and boxwoods), as they tend to be prone to winter burn.  Sometimes winter burn develops during the winter months, but spring is a prime time for symptoms to develop as plants start to photosynthesize and thus lose more water through stomates on needles and leaves.  So, as the ground begins to thaw and new needles and leaves begin to emerge, make sure evergreens are receiving sufficient water.  Established plants (those planted three years or more) require approximately one inch of water per week from rain or from supplemental watering with a drip or soaker hose placed at their driplines (i.e., the edges of where the branches extend).  Newly transplanted plants (those planted within the past three years) require roughly two inches of water per week.

Decontaminating pots.  If you grow plants in pots or other containers, and particularly if you have issues with root rots or other diseases caused by soil-borne pathogens, you should seriously consider decontaminating your containers before reusing them this year.  Empty any soil from the containers and discard the soil (especially if the plants previously grown in the containers have had disease issues), wash the containers thoroughly to remove any remaining soil, then soak the containers for 30 minutes in a 10% bleach solution (one part of a disinfecting bleach and nine parts water).  Rinse the containers thoroughly to remove any bleach residues and you’re ready to plant.  Note that this techniques works best for clay or ceramic pots, but may not be reliable for plastic pots.  Sometimes the best way to decontaminate plastic pots is to throw them away.

Mapping vegetable gardens.  For long-term success with vegetable gardening, crop rotation is a must.  Growing the same (or related) vegetables in the same spot in your vegetable garden year after year is a great way to build up disease-causing organisms in the soil.  These pathogens can cause problems for years, if not decades, to come.  So, if you haven’t been mapping out where you plant your vegetables each year, make this the year when you start doing that.  Buy some graph paper, draw your vegetable garden space to scale and preplan where you will plant your various vegetables this year.  Keep this plan as a reference so that next year when you create your 2022 map, you can properly rotate your vegetables to new areas in your garden.  If possible, don’t grow the same (or related) vegetables in the same area for a period of at least three to four years.

Keeping a garden journal.  Also, make this the year that you start documenting what goes on in your garden.  Record information on when plants emerge or begin to leaf out, and when they flower.  Keep track of the weather including temperatures, rain (and snow), significant storm events (hail, high winds, driving rains) and note when you see particular insects and diseases in your garden.  This sort of information can be very useful (particularly after you have several years’ data) in predicting insect pest and disease activity and thinking ahead about how to fend off these sorts of problems.

I hope these pointers help you have a successful 2021 gardening season.  For additional information on the PDDC and its activities, check out the PDDC website.  To learn about new PDDC education materials and programs, follow the clinic on Twitter or Facebook (@UWPDDC) or contact the clinic at pddc@wisc.edu and ask to be added to the PDDC’s listserv (UWPDDCLearn).

Elderberry Rust

What is elderberry rust?  Elderberry rust is a visually striking fungal disease that affects stems, leaves and flowers of plants in the genus Sambucus (i.e., elderberries).  The disease also affects sedges (Carex spp.).  On elderberries grown as ornamentals, as well as on sedges, the disease is primarily a cosmetic problem.  However, if elderberries are grown for fruit, the disease can disrupt flower and fruit formation, thus reducing fruit yield.

An elderberry rust gall on elderberry (left) and leaf spots caused by elderberry rust on sedge (right). Photos courtesy of Jenell Bindl (left) and Michele Warmund, University of Missouri (right)
An elderberry rust gall on elderberry (left) and leaf spots caused by elderberry rust on sedge (right). Photos courtesy of Jenell Bindl (left) and Michele Warmund, University of Missouri (right)

What does elderberry rust look like?  Elderberry rust is most noticeable on elderberries where it causes growth distortions and swellings (i.e., galls) on leaves and stems.  Galls are often very large, bright yellow and powdery from spores produced by the causal fungus.  In extreme cases, galls can resemble banana slugs that have attached themselves to branches.  Infected flowers become thick, swollen and green-tinged rather than white.  Affected plant parts are covered with a network of small (approximately 1/16 inch in diameter) ring-like spots.  These spots are reproductive structures of the rust fungus and produce the powdery spores that coat the galls.

On sedges, elderberry rust causes brownish leaf spots, often with yellow halos.  The spots eventually erupt releasing powdery, rusty-orange spores.

Where does elderberry rust come from?  Elderberry rust is caused by the fungus Puccinia sambuci, also known as Puccinia bolleyana.  The fungus overwinters in sedge debris, and spores produced in this debris blow to elderberry plants in the spring, leading to infection and gall formation.  Spores produced in elderberry galls blow back to sedges, where infection of newly produced leaves (and other plant parts) occurs.  These infections lead to spotting and to the formation of a third type of spore that reinfects sedges causing additional spotting.  Late in the season a fourth type of spore is produced that serves as the overwintering phase of the fungus.  Infection of both elderberries and sedges is favored by wet weather.

How do I save plants with elderberry rust?  Elderberry rust is not a lethal disease on either elderberry or sedge.  When galls form on elderberry, simply prune these out.  This will make elderberry plants more aesthetically pleasing and limit spread of the fungus to sedges.  When pruning, cut branches four to six inches below each gall.  Between cuts, decontaminate pruning tools by treating them for at least 30 seconds with 70% alcohol (e.g., rubbing alcohol straight out of the bottle), a spray disinfectant containing 60-70% active ingredient, or a 10% bleach solution (i.e., one part of a disinfecting bleach and nine parts water).  If you decide to use bleach, be sure to rinse your tools thoroughly after you are done pruning and then oil them to prevent rusting, which can be caused by bleach use.  Dispose of galls by burning (where allowed by local ordinance) or burying them.

How do I avoid problems with elderberry rust in the future?  In landscape settings, the best way to avoid problems with elderberry rust is to remove any sedges that are growing near elderberry plants.  The farther the distance between elderberries and sedges, the less likely that elderberry rust will be an issue.  Also, increase airflow around elderberry plants by thinning them and removing surrounding plants.  Increased airflow will dry plants more rapidly and make the environment less favorable for infection.  DO NOT use a sprinkler to water plants, as that wets leaves and provides a better environment for infections to occur.  Instead, use a soaker or drip hose to apply supplemental water to the soil at the drip lines of the plants (i.e., the edges of where the branches extend).  While fungicides are available for rust control in commercial elderberry production, these products are not recommended for use in home garden settings.

For more information on elderberry rust:  Contact your county Extension agent.

March 2021: Dampening Damping-Off: Tips on Seed Starting to Avoid Disease

Germinating Seed IconAfter a long, cold winter, it’s time to start growing plants from seeds for the upcoming growing season.  Damping-off is a common disease that can prevent seed-starting success.  Here are tips that can help prevent damping-off from being a problem.

Damping Off
Damping Off

Buy high quality seed from a reputable source.  High quality seeds are less likely to carry damping-off organisms.

Use pasteurized soil.  Pasteurized soil has been steam treated to kill pathogens.

Use clean pots/containers.  Store new pots or flats in sealed plastic bags to prevent possible pathogen contamination prior to use.  When reusing pots, soak them in 10% bleach (1 part of a disinfecting bleach, 9 parts water) for 30 minutes, then rinse well to remove bleach residues.

Plant seeds at the proper depth.  This will promote quick germination and rapid growth of seedlings out of the early stages of growth when they are most susceptible to damping-off.

Start seeds at higher temperatures.  This will again help plants grow out of their susceptible phase quickly.  Consider using a seed-starting heat pad (available at your local garden center), particularly if you start seeds in a colder part of your home (e.g., a basement).

Don’t overwater!  Damping-off organisms are more active in wet soils.  Water enough to keep seedlings alive, but keep plants a bit on the dry side to slow development of damping-off pathogens.

Seed starting can be a fun way to start the gardening season.  With just a little extra effort, you can prevent damping-off from dampening your gardening efforts.

For more information on damping-off and its management, check out University of Wisconsin Garden Facts XHT1124 (Damping-Off), available at https://pddc.wisc.edu/fact-sheet-listing-all/ or https://hort.extension.wisc.edu/articles/damping/.

Milkweed (Ornamental Plants Toxic to Animals)

Milkweed (Asclepias spp.) is a group of common herbaceous ornamentals that are an essential food source for caterpillars of the monarch butterfly (Danaus plexippus).  To increase monarch populations, people are increasingly planting ornamental types of milkweed and encouraging common milkweed to grow wherever it occurs in uncultivated areas.  While milkweed is beneficial to monarch populations, people need to be aware that it is toxic and can be lethal to animals, particularly horses and other equines.

Common milkweed (left) is often grown as an ornamental because it is an important food source for monarch butterflies (right).  Unfortunately, the plant produces compounds that are toxic to many animals, particularly horses.  Photos courtesy of Nancy Braschler (left) and PJ Liesch (right).
Common milkweed (left) is often grown as an ornamental because it is an important food source for monarch butterflies (right). Unfortunately, the plant produces compounds that are toxic to many animals, particularly horses. Photos courtesy of Nancy Braschler (left) and PJ Liesch (right).

What does milkweed look like?  Common milkweed (Asclepias syriaca) grows two to five feet tall and has broad, oval leaves that are five to nine inches long.  The leaves are smooth on top and somewhat velvety on the undersides.  Flowers, appearing in mid-summer, are pink to purplish and form rounded umbels (i.e., flower clusters).  Common milkweed produces prickly, four to six-inch long seedpods filled with brown to black seeds connected to silky white tufts that help the seeds float on air currents when they are released.

Other commonly planted milkweeds include swamp milkweed (Asclepias incarnata) and butterfly weed (Asclepias tuberosa).  Swamp milkweed grows three to six feet tall, has narrower, oval leaves (with a distinct pointed tip) and produces pink or purple flowers.  Butterfly weed grows one to two and a half feet tall, has narrow, pointed-tipped leaves that tend to be hairier than those of common milkweed, and produces yellow, orange or red flowers.  Several other species of milkweeds are found in Wisconsin, including whorled milked (Aesclepias verticillata), a white-flowered species that is particularly toxic and commonly found in pastures.

Why should I be concerned about milkweed?  The milky white sap that oozes from the broken stems and leaves of many types of milkweed is a latex that contains high concentrations of steroid derivatives called cardenolides (specifically cardiac glycosides).  These compounds are present both in live plants and in dried milkweed (which can sometimes be found in baled hay or in pastures after a plant is cut or dies).  Cardiac glycosides disrupt proper muscle (including the heart) and kidney function, the nervous system and the body’s acid-base balance.  While horses and other equines are most at risk for milkweed poisoning, all animals including chickens, cattle, sheep, dogs, cats, and even humans, as well as some insects, are susceptible to milkweed toxins.

Interestingly, monarchs cannot break down cardenolides and accumulate these compounds within their bodies.  The stored cardenolides give monarchs a bitter taste, making them unattractive to predators.

How will I know if my animals have been poisoned by milkweed?  Common symptoms of milkweed/cardenolide poisoning include depression; salivation; dilated pupils; weak, rapid pulse; labored breathing; loss of muscle control; muscle spasms due to not eating; convulsions; collapse and death.  Lethal doses of cardenolide occur at 0.05% of an animal’s body weight when dry plant material is eaten and 2% of body weight when fresh plant material is consumed.  For an adult horse, eating 2.2 lb of cardenolide is a lethal dose.  Death typically occurs approximately eight to 10 hours after ingestion.  If you suspect cardenolide poisoning, give affected animals fresh, non-contaminated food and immediately contact your veterinarian.

How do I prevent milkweed poisoning?  Inspect pastures and hay fields regularly for wild milkweed plants, and remove any you find promptly.  Because dried milkweed also contains toxins, do not feed animals hay that contains milkweed.  Provide adequate, good-quality forage for your animals.  DO NOT assume that horses and other livestock will not eat milkweed.

Swamp milkweed (left) and butterfly weed (right) are two other common milkweed species grown in home gardens.  Photos courtesy of Bridget Kelley (left) and Deb Andazola (right).
Swamp milkweed (left) and butterfly weed (right) are two other common milkweed species grown in home gardens. Photos courtesy of Bridget Kelley (left) and Deb Andazola (right).

If you are growing milkweed as an ornamental, DO NOT plant it near pastures or fence lines where livestock could potentially reach the plants.  Dispose of any milkweed plants that are removed during routine garden cleanup in a location far removed from livestock, so that animals are not able to feed on the dead plants

Milkweed spreads by underground rhizomes and through windborne seeds.  This can make proper management a challenge.  Herbicides can be effective for control, if you apply them at the correct time.  See UW Bulletin A3646, Pest Management in Wisconsin Field Crops (available at https://learningstore.extension.wisc.edu/) for products available for use in pasture settings.  When using herbicides, be sure to follow all label instructions to ensure that you are using the product in the safest and most effective manner possible and limit any adverse livestock exposures.

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

Tobacco Mosaic

Tobacco mosaic causing a blotchy light and dark coloring (mosaic) of tobacco leaves.
Tobacco mosaic causing a blotchy light and dark coloring (mosaic) of tobacco leaves.

What is tobacco mosaic?  Tobacco mosaic is a common viral disease of worldwide distribution that affects over 200 species of herbaceous and, to a lesser extent, woody plants.  Common hosts include tobacco, solanaceous vegetables (e.g., pepper, tomato) and vining vegetables (e.g., cucumber, melon, squash), as well as a wide range of ornamentals (e.g., begonia, coleus, geranium, impatiens, million bells, petunia).  The disease has its biggest impact on vegetables, where it can reduce yield and affect quality to the point that commercial crops cannot be marketed.

What does tobacco mosaic look like?  Symptoms of tobacco mosaic vary in type and severity depending on the plant infected, plant age, the variant of the virus involved, and environmental conditions.  On leaves, typical symptoms include blotchy light and dark areas (called mosaic); cupping, curling, elongation (strapping), roughening, wrinkling and other growth distortions; and smaller than normal size.  Fruits may have a blotchy color, ripen unevenly, be malformed or have an off flavor.  Entire infected plants are often stunted.  Other viral diseases like cucumber mosaic (see UW Plant Disease Facts D0036, Cucumber Mosaic) can cause symptoms similar to tobacco mosaic.  Often, multiple viral diseases can simultaneously affect a single plant.  Certain herbicide exposures (see UW Plant Disease Facts D0060, Herbicide Damage), nutrient deficiencies or toxicities, high temperature and even insect feeding can also cause similar symptoms.  Proper diagnosis of tobacco mosaic requires lab testing.

Where does tobacco mosaic come from?  Tobacco mosaic is caused by Tobacco mosaic virus (TMV), the first virus ever identified.  Numerous variants (strains) of the virus have subsequently been described.  TMV survives in infected plants (including viable seeds), as well as in debris from these plants.  Plant-based products (most notoriously tobacco products) can harbor the virus.  TMV is very stable and can survive for long periods of time; there are reports of TMV surviving and remaining infectious after 50 years in storage at 40°F.  Because of its stability, TMV can survive on and be picked up from hands, clothing, gardening tools, work surfaces and any other object (e.g., door knobs) that gardeners may handle.

TMV is highly transmissible and is commonly spread by handling infected plants, then healthy plants.  Spread via gardening tools is also very common.  No specific insects spread TMV (the way that aphids spread Cucumber mosaic virus).  However, bees and chewing insects (e.g., grasshoppers) can transmit TMV through casual contact or their feeding as they move from plant to plant.

Leaf growth distortions caused by tobacco mosaic.
Leaf growth distortions caused by tobacco mosaic.

How do I save a plant with tobacco mosaic?  There is no cure for tobacco mosaic.  Once infected, plants remain infected for life, and typically the virus spreads throughout the plant from the point of infection.  Infected plants and any associated debris should be burned (where allowed by local ordinance) or double-bagged and disposed of in a landfill.  DO NOT compost plants with this disease.  Thoroughly decontaminate any items that have come into contact with infected plants or their debris by treating them for a minimum of one minute with:

  • 2.75 tablespoons Alconox® (a lab detergent) plus 2.5 tablespoons sodium lauryl sulfate (SLS), also known as sodium dodecyl sulfate (SDS), in one gallon of water, or
  • 14 dry ounces of trisodium phosphate in one gallon of water.

These ingredients can be ordered on the internet.  If you decide to use SLS (SDS), be sure to wear gloves, safety goggles and a dust mask, and mix the solution in a well-ventilated area as SLS (SDS) is a known skin and eye irritant.  Once treated, rinse items with sufficient water to remove any residues.  Also, thoroughly wash your hands with soap and water, and launder any clothing that you wore while disposing of infected plants and debris.

How do I avoid problems with tobacco mosaic virus in the future?  Inspect plants prior to purchase for any symptoms of tobacco mosaic, and DO NOT buy symptomatic plants.  Purchase seed from a reputable supplier that routinely inspects their seed-producing plants for symptoms of viral (and other) diseases.  If you use tobacco products, DO NOT use them around plants.  Also, wash your hands thoroughly with soap and water prior to handling plants, and consider wearing freshly laundered clothing when gardening.  Finally, decontaminate (as described above) any items that might harbor TMV to help prevent spread.  Even if you do not use tobacco products, routine handwashing and decontamination of gardening tools and other items can help prevent tobacco mosaic from being a problem.

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

Growing Vegetables in Containers

Container gardening is an increasingly popular way for home gardeners to grow their favorite vegetables, particularly when gardening space is limited.  Containers can be placed on a windowsill, patio, deck or balcony, or in any place where growing conditions are appropriate for producing vegetables.  Containers can be easily moved from place to place to take advantage of changing weather conditions (e.g., rain, sunlight), and their proximity to a home makes caring for plants and harvesting vegetables easy and convenient.  The following are some pointers on how to ensure success when container gardening.

Containers are a convenient place to grow your favorite vegetables and herbaceous ornamentals.
Containers are a convenient place to grow your favorite vegetables and herbaceous ornamentals.

What types of vegetables can I grow in containers?  Almost any vegetable can be grown in a container given the right variety and container size.  However, determinate, dwarf and compact vegetable varieties often work best.  Vegetables like arugula, kale, lettuce and spinach work well in containers because they are easy to seed, can be harvested frequently, and can be replanted throughout the season.  Smaller vegetables such as beets, carrots, radishes and turnips also grow well in containers because the loose, well-drained potting mixes used for container gardening allow roots to grow easily.  When growing root vegetables, be sure to space plants two to four inches apart to allow roots to form properly.  As an added bonus, the greens of root vegetables are not large, do not need support, and are very attractive.  Vining plants like cucumber, peas, melons and squash can be grown in containers with proper supports (e.g., trellises).  Alternatively, there are bush or hanging varieties of these vegetables that do well in containers.  Tomatoes (properly staked or caged), peppers, and eggplant grow especially well in containers and can be mixed with herbs or flowers for added visual appeal.  For a list of suggested vegetables for containers, see University of Wisconsin Garden Facts XHT1273, Vegetable Varieties for Containers.

What sort of container should I use?  Choosing the right type of container for the vegetables that you decide to grow is very important.  Containers should have the right volume and depth to support plants once they are fully grown.  In general, smaller plants like leaf lettuce, spinach, peas, radishes, cilantro, and green onions require containers with a volume of at least two gallons and that are at least four to six inches deep.  Larger plants like tomatoes, peppers, broccoli, eggplants, squash, cucumbers and bush beans require a container with a minimum volume of five gallons and a depth of 12 to 18 inches.  Many types of containers are available for growing vegetables including (but not limited to) 5-gallon plastic buckets, plastic pots, plastic storage containers, terra cotta/clay and ceramic pots, concrete and wooden planter boxes, wooden barrels, bushel baskets, plastic bags, grow bags and self-watering containers.  Make sure that the container you select has a drainage hole.

If you are reusing containers, be sure to decontaminate them prior to use, particularly if you previously have had problems with root rots (see University of Wisconsin Garden Facts XHT1072, Root Rots in the Garden) or damping-off (see University of Wisconsin Garden Facts XHT1124, Damping-Off).  Rinse pots to remove clinging bits of soil, then soak them in 10% bleach (a formulation designed to disinfect) for 30 minutes.  Then rinse containers to remove any bleach residue.  This treatment may not consistently be effective for plastic containers.  You may have to replace these containers if disease issues persist.

What sort of soil should I use?  Commercial potting mixes work well for most vegetables.  They are typically light weight, high in organic matter and well-drained, containing a combination of compost, peat moss, bark, perlite or other similar materials.  Read the label before purchasing a potting mix to determine its composition.  When possible, select a product that has been pasteurized to reduce the risk of diseases caused by soil-borne pathogens.  Consider adding a slow-release fertilizer, if there is not one included in the mix.  Bagged potting mixes come in easy-to-handle sizes:  1, 2, or 2.8 cubic feet (7.5, 15 and 21 gallons respectively).  Fill your container completely with planting mix for optimal drainage.  DO NOT put anything (e.g., rocks, broken pot pieces, etc.) in the bottom of the pot.  Research shows layering materials in a container impedes drainage; water moves best through a continuous column of soil mix.

Leafy vegetables like kale are easy to seed in containers, can be harvested frequently, and can be reseeded throughout the season.
Leafy vegetables like kale are easy to seed in containers, can be harvested frequently, and can be reseeded throughout the season.

How do I care for my plants?  Place your containerized plants in full sun (i.e., a minimum of six hours per day) with easy access to water.  Initially, when plants are small, you will not need to water much.  However, as plants increase in size, the temperature increases, and the plants start to produce fruit (e.g., tomatoes, peppers, eggplants, zucchinis, cucumbers), you will need to water daily.  You may also need to fertilize.  If so, use a fertilizer designed for growing vegetables, and follow the instructions on the label to determine how much and how frequently to apply.  Harvest leafy greens such as kale, mustard and lettuce on a regular basis, and reseed as needed.  If plants fail, remove and replace them with other vegetables that fit the space and have time to grow to harvest.  Greens, radishes, bush beans, and cilantro are fast-growing filler vegetables that you can grow from seed.

For more information on growing vegetables in containers:  See University of Wisconsin Garden Facts XHT1273, Vegetable Varieties for Containers or contact your county Extension agent.