I really love this time of the year as plants emerge once again after their long winter naps.  I also love the fact that I now get to start looking once again for some of my favorite plant diseases.  At the top of the list at this time of the year are the rust diseases.  Rusts encompass a large group of fungal diseases, where the fungi produce brightly-colored (yellow to orange to bown) spores.  Each rust fungus has a very specific host range.  The following are a few of the rusts (one on a broad-leafed tree, one on a conifer and one on an herbaceous plant) that I have recently seen either through the clinic or in my own yard.

Crown Rust

Crown rust is classic rust of grass species such as turfgrass and oats.  If you’ve ever walked through your lawn and gotten orange shoes, you’ve encountered this disease.  The fungus that causes crown rust is Puccinia coronata, which has several variants adapted to infect specific grass hosts.  The disease and pathogen names come from the look of the resting spores of the fungus.  These spores have spikes that give them the appearance of a crown.  At this time of the year, I don’t see crown rust on grass or oats (that comes later in the growing season), but I see it on a second host (called the alternate host) of the fungus, buckthorn.  Buckthorn is actually required by the crown rust fungus to complete its life cycle.  Puccinia coronata causes yellow-orange, powdery patches on the buckthorn leaves and green stems, and I actually use crown rust as an ID feature for buckthorn.  If I see seedlings that I think are buckthorn, but I’m not quite sure, I look for the characteristic orange patches of crown rust to confirm.  And if you need another reason get rid of buckthorn, in addition to this plant being incredibly invasive, here it is.  If you remove buckthorn, you will prevent the crown rust fungus from completing its life cycle and reduce the severity of the disease on turf and oats.

Weir’s Cushion Rust

This is rust disease of spruce that I see infrequently, but I just received a sample of it this past week in the clinic.  I was over the moon!  (Yes, I know I’m weird and lead a very sheltered life.)  The fungus that causes this disease is Ceropsora weirii (formerly Chrysomyxa weirii), a single-host rust fungus that only requires spruce to complete its life cycle.  Infection leads to yellow banding on one-year-old needles.  Within these bands in the spring (typically April or May), fruiting bodies (i.e., reproductive structures) of Ceropsora weirii form yielding orangish spores that blow to newly emerging needles where the fungus infects.  The fruiting bodies are easily visible with a hand lens or even with the naked eye.  Eventually the infected3 needles brown and drop off the tree.  Management of Weir’s cushion rust can be a challenge and typically involves use of fungicides to protect newly emerging needles.

Mayapple Rust

I’d like to give a shout-out to Brenda Dahlfors, Master Gardener Program Coordinator with University of Illinois Extension for sending me photos of this cool rust.  The fungus involved here is another species of Puccinia, Puccinia podophylli.  This is another single-host rust, where the fungus that only infects mayapples.  The disease is most visible in the spring when bright orange, powdery patches develop on the undersides of leaves.  On the upper leaf surfaces above these patches, you will see yellow spots/discolored areas.  The orange spores produced by the pathogen reinfect mayapple plants, causing additional disease.  The bright orange patches tend to fade to a duller brown as they age and convert to producing brown overwintering spores.  These overwintering spores germinate in the spring to produce yet another type of spore that causes the initial infections in the spring.  Careful removal of infected leaves and plant debris (burn, bury or hot compost this material) combined with fungicide sprays where appropriate is the typical management strategy for this disease.

Need additional information?

These are just a few of the cool rust diseases that you may encounter as you are out and about.  Watch for these and other rusts, and enjoy them when you find them.  There are the most visually colorful and attractive diseases that I see.  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).

I 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.

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).

As 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.

Need help?

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).