Kansas State University

By: Judy O’Mara

A little unusual… this past week a fungal disease called southern blight took out a landscape planting of Lamium or dead nettle in south central Kansas. In my years at K-State, I’ve seen southern blight occur on hosta plantings a few times and  have also picked it up on Echinacea, Hibiscus, Liatris, Pasque Flower, Penstemon, Rudbeckia, Solidago, as well as, tomato. Southern blight (Sclerotium rolfsii; Athelia rolfsii) is a serious disease, particularly in the south (hence the name). It has a history of being damaging to over 500 plant species including field crops, vegetables, flowers, weeds, and even some woody landscape plants.

Plants infected by the southern blight fungus may wilt quickly and collapse, or they may turn yellow and slowly decline. There are frequently dark stem lesions at the base of the plant, a crown rot and/or a root rot. The most distinctive symptoms of southern blight are the presence of sclerotia and a white matt of fungal mycelium. Sclerotia are small seed-shaped fungal structures that allow the disease to survive in plant debris and soil for several years. They range in color from light tan to reddish-brown becoming somewhat inconspicuous as they age. A fan of white mycelium may grow along the basal stem lesion or in the soil.

While southern blight is a serious disease, it is not that common in Kansas. When it does occur here, it tends to show up during July and August under hot, wet conditions. The limiting factor for Kansas may be that when we have high temps, it also tends to be dry. Southern blight outbreaks in Kansas have been observed in irrigated landscapes (ie hot + wet). Crowded plantings can create a humid environment that can favor the disease.

Once southern blight shows up in the landscape, it can be a challenge to manage. Infected plants (plus the root ball) should be dug up, bagged and sent to the landfill. Do not compost plants from infested locations, as this can spread the disease across the planting area when the compost material is re-incorporated into the landscape. Rotate out of the infested area for 3-4 years, but make sure to control weeds because they can also serve as a host for the disease.

The bulk of the sclerotia will survive in the upper soil, so deep plowing or inverting the soil can help to reduce the amount of disease in the infested area. Another strategy for reducing southern blight severity, is to employ solarization of the target area. This can be done by covering the area with clear plastic for 4-6 weeks. It will be important to clean and disinfect tools, gloves and shoes after working in areas with southern blight. This will help to limit movement of the disease into new areas of the garden or landscape.

An article in the University of Illinois Home Yard and Garden Pest Newsletter indicated that they are also seeing southern blight activity this summer, particularly on Hosta. Another name for the disease is Hosta Petiole Blight. The article has some great photos of the disease on Hosta, which can be seen at http://hyg.ipm.illinois.edu/article.php?id=1087.

By: Judy O’Mara

Powdery mildew is a common disease on many ornamentals. It is easy to identify because it produces a whitish-gray mold on the surface of the leaf. This fungal disease is favored by high humidity and crowded plantings (i.e. poor air flow). Powdery mildew doesn’t kill the plant but susceptible hosts that have a chronic problem with it can be weakened.  The best management strategy is through the use of resistant varieties.

The Home, Yard & Garden newsletter from the University of Illinois has a nice article on powdery mildew this week: http://hyg.ipm.illinois.edu/article.php?id=1092

***Picture provided through University of Illinois Home, Yard, & Garden newsletter.

Rose Rosette Virus…What does it look like?

By: Judy O’Mara

We’ve had several reports of rose rosette virus in the K-State Plant Disease Diagnostic Lab this spring. It is not hard to identify based on symptoms. Basically, the growth on the plant becomes increasingly deformed. It starts with an individual rose cane that either elongates, or gets bunchy with lots of shoots (witches broom). The foliage can be reddish-purple or green and strappy (see below). Very characteristic for rose rosette virus is the production of excessive thorns along the canes of the deformed shoots. Symptoms on the plant get worse over a few weeks. In an odd way, it can sometimes look like a bridal bouquet.

Left unchecked rose rosette virus will kill the infected plant and continue to spread to nearby roses via its insect vector (Phyllocoptes fructiphilus), an eriophyid mite. This tiny mite is not visible to the eye, resides in new growth and crevices, and is spread by the wind.

Pruning out deformed portions of the plant is not an effective control strategy as the disease can overwinter in the roots. Upon seeing symptoms, infected plants should be dug up (including the root ball) bagged, and removed from the site.

For more information on this disease see the K-State fact sheet on rose rosette virus.

Rose Mosaic Virus…How do you spot it?

By: Chandler Day

Have you seen yellow oak leaf or netted patterns on your rose bush leaves? If so, you most likely have a disease called Rose Mosaic Virus. This rose disease is relatively common in Kansas landscapes and symptoms can vary from wavy yellow lines or ring spots to mottled oak leaf and mosaic patterns. Rose Mosaic Virus spreads through vegetative propagation and does NOT move around via insects or mites. Another rose disease, rose rosette virus, will kill the infected rose plants, while rose mosaic virus disease will not. Plants infected with rose mosaic virus will produce symptoms on the rose plant every year for the remainder of its life.

The best ways to prevent viral diseases on your rose bushes are to start by buying non-symptomatic plants that have leafed out, or certified disease-free roses. Symptomatic plants in the landscape should be dug up (with the root ball), bagged and discarded.

Photos by Megan Kennelly/KSU

Rose Garden Observations and Recommendations (Coming Soon)

By: Brooke Garcia

Following an extremely wet spring, I’ve noticed several roses to be impacted by Black Leaf Spot. With continuous rainfall and high humidity, this fungal disease thrives. As this fungal disease develops, you can begin to notice black spots on the leaves. The leaves often times will turn yellow, eventually dropping from the plant. An easy way to spot this on plants (despite seeing the dark black spots and yellowing leaves) is to look at the bottom of the plant. The bottom portion of the rose shrub will most likely look bare, without leaves.

Despite having all of our recent rains, I’ve noticed some roses appear to be performing well given the circumstances. My recommendations are purely coming from an observational standpoint. On the other hand, many of these roses in particular were surrounded by other rose plantings that were impacted by both Black Leaf Spot and Rose Rosette Virus.

Here are the following rose recommendations:

• ‘Honey Perfume’
• ‘Princess Charlene De Monaco’ Hybrid Tea Rose
• ‘Coral Drift’
• ‘Lemon Drift’
• ‘Top Gun’

By: Michael Bear

Heat is one the leading causes of weather-related deaths and injuries in the United States. Excessive heat causes hundreds of deaths every year. Heat can affect people in a variety of settings and while dangerous heat is associated with the summer season, it can occur in the spring and fall as well.

The risk

When exposed to high temperatures your body sweats, which evaporates to cool your body. Hot and humid weather challenges your body’s ability to cool itself because your body sweats a great deal to try to maintain your body temperature. Over time this increased sweating leads to dehydration and your body temperature becomes elevated. Increased levels of humidity make this worse as the high water content of the air hampers the evaporation of sweat on your skin. This can result in heat exhaustion or heat stroke. Those most at risk for heat illness include infants, children, the elderly, overweight people and those who are ill or have certain medical conditions such as high blood pressure.

Heat exhaustion

Heat exhaustion is a mild form of heat illness that may develop after days of exposure to high temperatures and inadequate fluid intake. If not treated, heat exhaustion may become heat stroke. A person suffering from heat exhaustion may have cool moist skin. Their pulse rate will be fast and weak and their breathing will be fast and shallow. Additional warning signs of heat exhaustion include:

• Heavy sweating
• Paleness
• Muscle cramps
• Tiredness
• Weakness
• Dizziness
• Headache
• Nausea or vomiting
• Fainting

Heat exhaustion first aid

• Drink cool beverages without alcohol or caffeine.
• Move to an air-conditioned environment.
• Take a cool shower, bath or apply cold compresses.
• Rest

Heat stroke

Heat stroke is the most serious of heat-related illnesses. It occurs when the body is unable to cool itself because the ability to sweat fails. A victim’s body temperature will rapidly rise within a few minutes. Heat stroke can cause death or permanent injury if it is not treated quickly. Warning signs of heat stroke vary but can include:

• An extremely high body temperature — above 103 degrees Fahrenheit.
• Red, hot and dry skin without sweating.
• Rapid, strong pulse.
• Throbbing headache.
• Dizziness.
• Nausea.
• Confusion.
• Unconsciousness

Heat stroke first aid

• Call 911 immediately. Untreated heat stroke may result in death or disability.
• Move the victim to a shady and/or air-conditioned area.
• Cool the victim rapidly using whatever means available such as a cool shower or bath, garden hose, or sponging with cool water.

Prevention

Like many hazards, there are steps you can take to avoid becoming a victim of heat illnesses:

• Drink lots of water and avoid alcohol and caffeine.
• Limit strenuous outdoor activities.
• Wear light colored, light weight clothing.
• Use sunscreen.
• Take breaks in the shade as often as possible.
• If working in the heat, increase workloads gradually. Allow new employees and workers who have been off for more than a week more frequent breaks.
• Change your schedule so outdoor work is performed early or very late in the day.
• NEVER leave kids or pets in vehicles.
• Check on the elderly, sick and those without air conditioning.
• Be aware of the symptoms of heat illness and take action if you see someone at risk.

Sources

• National Weather Service Heat Safety Tips and Resources page
• Centers for Disease Control and Prevention Heat-Related Illness page

Dividing Daylilies

By: Brooke Garcia

My backyard is currently a construction zone, and I have spent the last month dividing iris and daylily plants in efforts to save them from being ran over by the Bobcat (and no I’m not talking about the animal). With our future garage being built, we have had to move hundreds of iris and daylily plants into a new garden bed. Being a horticulturist by trade, I couldn’t see these plants go to waste.

I know it isn’t the ideal time to be moving these plants around, as several of them have recently bloomed. Generally, I’d suggest to wait to divide these plants until they have completed their bloom cycle (late summer/early fall). You can also divide them in the early spring prior to blooming, but this could impact their blooms later in the season. The steps to this process are relatively simple, but you should expect your hands to get a little dirty. It can also be a little time-consuming.

Step 1: Dig up a clump of daylilies with a shovel or hand trowel. I have found the process moves more quickly when you grab a shovel and do larger sections. In our case, we had hundreds to move…. so the bigger the clumps, the better!

Step 2: Trim the daylily leaves and flowers to a height of 8-12 inches. Pictured above on the right, you will notice the final clump cut back to approximately 12 inches.

Step 3: Separate the clump of daylilies into smaller clumps. My preference is to keep the clumps in groups of 2-3 plantings to keep the transplant looking full. Looking at the pictures below, the bottom left shows a single plant divided from the clump of daylilies. Pictured on the bottom right, I kept two plants clumped together for one single planting.

Step 4: Loosen the soil away from the roots of the recently divided plants. Next, trim the roots of your plants to stimulate new root growth. Only trim a small amount of the roots, as this will be enough to stimulate new healthy growth. (See pictures below)

Step 5: You’re ready to plant your newly divided daylilies! Be sure that you choose a sunny location in your garden with well-drained soil. Generally, I dig a hole 2-3x the size of the root ball of my plant. Once you place your newly divided plant into its newly dug home, add additional compost or garden soil into the hole. Gently pack the soil around the new planting. Be mindful to keep the crown of the plant above the soil line.

Step 6: Don’t forget to water your freshly divided daylily plants. If you plan to transplant more, space the plantings 12-18 inches apart to give them room to grow. Daylilies can begin to get crowded after 4-5 years.

Daylily Leaf Streak

By: Judy O’Mara

Daylilies are a great fit for Kansas. There are many varieties that grow well here. I particularly like browsing the photo gallery at the Flint Hills Daylily Society chapter (https://www.flinthillsdaylily.org/gallery) for my favorite ones. They are mostly problem free but I did recently see some daylily streak (Aureobasidium microstictum) on a recent walk. It isn’t that common in Kansas, but wet conditions this spring likely the triggered the disease.

Daylily leaf streak starts as long yellow streaks that turn a reddish brown. Heavily infected leaves scorch back and die early.

The disease is favored by moderate temperatures and wet conditions. Daylily streak can spread by splashing water droplets. Although you can’t manage the rain, you can time irrigation so that your plants are watered in the morning. This allows leaves to dry out quickly and reduce conditions that favor disease development. A mature daylily planting can be crowded leading to poor air circulation and prolonged periods of leaf wetness. Good plant spacing will improve air flow and help to dry out plants quickly. The disease can also be moved on tools, so avoid working around wet plants

Inspect plants when purchasing them and always start with healthy, disease-free plants (ie no spots on the leaves). If just one plant in the landscape is showing symptoms, you might be able to stay ahead of the disease by picking off and dispose infected leaves. Daylily leaf streak will overwinter in the leaf litter, so cleaning up the flower bed will help to reduce the amount of disease that is carried over to the next growing season. If daylily leaf streak shows up annually, it might be worth isolating the problem daylily from the rest of the planting.

The best strategy for managing day lily leaf streak…is through the use of resistant cultivars. Disease susceptibility varies and lists of resistant varieties are not easily available. A few varieties reported by Clemson University are: Betty Bennet, Edna Spalding, Ella Pettigrew, Globe Trotter, Nancy Hicks, Pink Superior, Ron Rousseau, Sudie, Tropical Tones, Upper Room, and Winsome Lady. (https://hgic.clemson.edu/factsheet/daylily-diseases-insect-pests/)