UAEX Plant Health Clinic

🌸 Seeing brown, dusty spots on the undersides of your snapdragon leaves? It could be snapdragon rust!

We recently diagnosed snapdragon rust in the Arkansas Plant Health Clinic. This fungal disease thrives during cool, humid conditions and can spread quickly when leaves stay wet for long periods.

The first signs of infection often appear as pale-yellow spots on the upper leaf surface. Turn the leaf over, and you’ll find the classic symptom—small brown, powdery pustules that contain spores capable of spreading the disease to other snapdragon plants. As the disease progresses, leaves may yellow, dry up, and drop prematurely.

To help reduce rust problems:
🌿 Clean up plant debris
💧 Avoid overhead watering and water at the base of plants when possible
🌬️ Space plants properly to improve air movement and help leaves dry more quickly

Snapdragon rust won’t usually kill your plants, but it can make them look much less attractive. Checking the undersides of leaves is key—those brown, dusty pustules are a dead giveaway!

Not everything growing on a plant is causing disease! 🍫

This chocolate-colored growth on a snap bean leaf is chocolate tube slime mold (Stemonitis spp.), a fascinating slime mold that feeds on decaying organic matter and microorganisms. Despite its appearance, it is not a pathogen and does not harm the plant.

Slime molds often appear after periods of warm, humid weather and are more of a curiosity than a concern. Nature is full of surprises!

🍿 Seeing “popped popcorn” instead of juicy mulberries? Your tree may have popcorn disease — a fungal disease that infects the fruit and causes berries to become enlarged, white, and puffy. In the photo above, you can see the healthy fruit on the left and the diseased fruit on the right.

The good news: this disease only affects the fruit, not the health of the tree itself. However, it can be very frustrating if you were hoping to harvest berries.

🛠 Management Tips:
• Remove infected fruit from the tree
• Rake up and destroy/dispose of fallen infected berries
• Good sanitation is key, since the fungus can overwinter in infected fruit and reinfect the following season

While sanitation can be tedious, especially with large trees, it is currently the most practical management approach for homeowners.

Photo credits: Drew Johnson

Winter injury impacts are still showing up across Arkansas on trees and shrubs. Rapidly fluctuating temperatures this winter — especially the shift from temperatures in the 70s–80s in March to below freezing overnight — caused significant stress to many plants. 🌡️➡️❄️

Many plants had already started pushing new growth, and that tender new tissue is not cold hardy. When temperatures suddenly dropped, the freezing conditions damaged the young plant tissue, leading to dieback and injury that we’re still seeing today.

The photo shows an example on boxwood: the light-colored, papery leaves are new growth that emerged before the mid-March freeze and was damaged by the cold.

Winter injury can have widespread impacts and may explain many symptoms we’re seeing this season, though additional issues can sometimes occur on top of this stress.

Come see our mobile diagnostic lab at the Garland County Master Gardener Plant Sale and Garden Show tomorrow (Saturday), April 25 from 9am - 4pm at the Garland County Fairgrounds Building #5! Bring your plant samples and questions for on-site diagnostics and consultations 🌱🌳🪻

Curious about what we do at the Arkansas Plant Health Clinic?
Want to see where our mobile diagnostic lab will be traveling across Arkansas in April for on-site plant problem diagnosis? 🌿🔬
Check out this recent article from the Arkansas Cooperative Extension Service to learn more: https://www.uaex.uada.edu/media-resources/news/2026/april/04-01-2026-ark-plant-health-clinic.aspx

‼️Large Patch Disease in Turf is no April Fools‼️: For lawns affected by large patch disease (caused by the fungus Rhizoctonia solani), we are currently in the recommended window for spring fungicide applications! A treatment made between March 15 and April 15 will help suppress the disease and protect turf before the fungus goes dormant in the hot summer weather. Applying fungicides during this spring period (the period when the fungus is active) is an important step in reducing disease severity and promoting healthier turf.
For treatment, landscapers or commercial applicators can use Headway (propiconazole+azoxystrobin), Tourney (metconazole), Trinity (triticonazole), Triton (triticonazole), Pedigree (flutolanil), or Lexicon (fluxapyroxad + pyraclostrobin). These products are labeled for both home lawns and golf courses. Homeowners may use 'Spectracide Immunox Fungus Plus Insect Control for Lawns', 'Scotts Lawn Fungus Control', 'Scotts Disease EX Lawn Fungicide', or 'Bonide Infuse Systemic Disease Control Lawn and Landscape'. Follow all label directions.

Photo: Large patch symptoms in a Zoysiagrass lawn (Jim Robbins, University of Arkansas System Division of Agriculture)

🎃 Pumpkins on the porch and colorful leaves in the trees — fall is here! 🍁

Noticing some spots or blotches on your tree leaves? Don’t worry — that’s fairly common this time of year. As trees prepare to drop their leaves, a few fungal leaf spots won’t cause significant harm to the tree.

🍂 Just rake up and dispose of fallen leaves to help reduce disease carryover into next spring.

Enjoy the season — and your trees will thank you next year! 🌳

Photos: Tar spot on maple (Andrej Kunca, National Forest Centre - Slovakia, Bugwood.org) and Tubakia leaf spot on oak (Jason Sharman, Vitalitree, Bugwood.org)

🎃 Did you know that pumpkins can get sunburned too?

Pumpkins can lose their leaves for a variety of reasons, including disease, pest infestations, or environmental stress. 🍃🍂 One of the most common diseases affecting pumpkin foliage is powdery mildew, a fungal infection that causes white, powdery spots on leaves and eventually leads to their death and drop. Insect pests, such as squash bugs and cucumber beetles, can also damage leaves by feeding on them or transmitting pathogens. 🪲 Drought stress or nutrient deficiencies may further weaken the plant, making it more susceptible to both disease and pest attacks.🪾

When the leaves are lost, the fruit—normally protected by the canopy—becomes exposed to direct sunlight. ☀️ This sudden exposure can cause sunscald, a condition in which the fruit’s surface overheats and the skin becomes discolored, leathery, or even cracked. 🏜️ The damaged tissue not only affects the pumpkin’s appearance but also compromises its natural protective barrier. As a result, secondary pathogens, such as fungi and bacteria, can easily colonize these weakened areas, leading to rot and decay. 🍄‍🟫🦠 Over time, this can significantly reduce the fruit’s quality, shelf life, and marketability.

To prevent these issues, it’s important to maintain healthy foliage through proper watering, crop rotation, good air circulation, and timely disease management. Keeping the plant vigorous and the leaves intact helps protect the developing fruit and ensures a more successful harvest. 💦🎃🌱

Photos by Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org

In Arkansas, the ideal time to plant trees and shrubs is during the fall season. 🍂🌳 Cooler temperatures and increased rainfall allow new plantings to establish strong root systems before the heat of summer returns. This gives trees and shrubs the best chance for long-term health and growth. 🌱

While arborvitaes (Thuja spp.) are popular evergreen choices in other regions, they often struggle in Arkansas's challenging climate. The combination of hot, humid summers, occasional drought, and heavy clay soils can cause significant stress on arborvitaes, making them susceptible to pests (like bagworms), diseases (such as root rot and blight), and premature decline. 🐛🌿 As a result, many arborvitaes planted in Arkansas do not thrive or live as long as expected. 🥀

If you’ve already had arborvitaes die in a specific area of your landscape, it is strongly advised not to plant more arborvitaes in the same location. The underlying environmental conditions that contributed to the initial plant’s failure—whether poor drainage, unsuitable soil, or local disease presence—will likely cause problems for future arborvitaes as well. 🪾

To explore proven alternatives to arborvitae that are well-suited for Arkansas landscapes, consult this UADA article:
https://www.uaex.uada.edu/yard-garden/home-landscape/MP510%20hedge.pdf

To learn more about tree care in Arkansas, see these UADA articles:
https://www.uaex.uada.edu/yard-garden/home-landscape/fall-landscaping/tree-care.aspx
https://www.uaex.uada.edu/yard-garden/resource-library/plant-week/planting-trees-10-24-14.aspx