If you're a seasoned green thumb, you're probably already pretty good at identifying when tree diseases take hold of your favorite oak or spruce. Perhaps the leaves are discolored, or there's an unusual growth pattern, or fruit is not bursting forth from your fruit trees like it used to. Identifying a tree disease is a tricky yet vital skill for keeping your trees rooted in your landscape for years to come, so if you're ready to play plant doctor with your troubled garden favorites, read on! We're digging deep into the world of tree health to explore how you can prevent tree diseases from ravaging your Iowa landscape.

Understanding Tree Diseases

What are Tree Diseases?

Many common tree ailments are caused by pathogens such as fungi, bacteria, and viruses. These microscopic nuisances invade trees, disrupting their normal functions and often leading to visible symptoms. If left untreated, your tree could even die back completely. Environmental factors like poor soil conditions, drought, and mechanical damage can make trees more susceptible to these diseases, which is why proper ongoing care is essential for long-term health. 

Common Symptoms

To spot tree diseases early, you'll need to be familiar with these common symptoms:

• Discolored Leaves: Yellowing, browning, or mottled leaves are a sure sign that your plant is under stress. This symptom can occur for multiple reasons, including over or underwatering, heat stress, nutrient deficiencies, and disease.
• Unusual Growth Patterns: Watch for abnormal growth patterns, such as galls, cankers, or stunted growth, as these can also indicate disease and infections.
• Bark Abnormalities: Cracking, peeling, or discolored bark is also a common sign of disease or pest infestation.
• Wilting: Watch for sudden wilting of leaves or branches, as this often points to root problems or vascular diseases.

Common Tree Diseases in Iowa

Oak Wilt

Identification: Leaves turn dull green, wilt, then brown, starting at the leaf margins. The disease often spreads through root grafts between neighboring trees.

Prevention: To keep your oak healthy and resilient, avoid pruning or wounding the root system during the growing season. You should also avoid planting the same oak species close together and choose more resistant species like the Bur or White Oak.

 

Cedar-Apple Rust

Identification: This fungus alternates between cedar and crabapple/apple trees. Look for bright orange, gelatinous galls on your cedars and yellow spots on your crabapple/apple tree's leaves, especially after rain or, humid weather., or a generally wet season. 

Prevention: Remove galls from cedar trees and use fungicide sprays on apple trees during the growing season. Avoiding planting these two species together and ensuring adequate air circulation will also lessen the symptoms of cedar-apple rust.  If you have an apple/crabapple tree with rust, clean up all of the fallen leaves in autumn and dispose of them so the disease cannot overwinter. 

Shrub, Tree, and Perennial Diseases to Watch For

 

Powdery Mildew

Identification: White, powdery coating appears on leaves, stems, and buds. It thrives in warm, dry conditions and affects a variety of plants and trees.

Treatment: Increase air circulation around your plants by spacing them appropriately and pruning affected areas. We also recommend using fungicides if necessary.

Rust

Identification: Rust is a group of fungal diseases that causes orange, yellow, or brown pustules on the undersides of leaves. It often affects roses, daylilies, and hollyhocks, but it can also affect trees.

Treatment: Remove and destroy infected leaves and use fungicides to protect healthy plants.

Treatment and Prevention

General Treatment Methods

For tree, shrub, and perennial diseases, common treatments include:

Fungicides: Fungicides are effective against many fungal diseases if applied correctly and at the right time. Most fungicides work best as preventatively, rather than curatively. This means scouting for signs of disease and applying fungicides early to stop them from spreading. 

Soil Management: Ensure proper drainage and nutrient levels to keep your plants healthy and boost their disease resistance. There are a few fungicides for soil-borne diseases that can be applied as a drench. See our horticulturist in store for recommendations. 

 

Preventative Strategies

Regular maintenance is key to protecting your landscape, as ensuring the overall health of your plants is your best weapon against tree diseases. Make sure you're providing the required light, water, and nutrient needs for your trees. We also recommend using the following best practices for maintaining healthy trees in your Iowa backyard:

• Proper Pruning: Remove diseased branches and dispose of them properly to prevent the spread of pathogens. Remember: it's always better to make any major pruning cuts during your plants' dormant periods to avoid additional stress.
• Choosing Resistant Varieties: Select trees, shrubs, and perennials that are known to be resistant against Iowa's most common tree and plant diseases.
• Monitoring: Regularly inspect your plants for signs of disease and act promptly if you notice anything unusual.

DIY Solutions vs. Professional Help

While minor issues can often be handled with DIY solutions, such as homemade fungicide sprays, commercial fungicides from Wallace's, or manually removing affected areas, some situations require professional intervention. If a tree is large, valuable, or heavily infested, it's best to call an ISA-certified Arborist.

We hope you now feel more confident in your ability to spot and treat common tree diseases in your yard. Remember: a little knowledge goes a long way in maintaining a healthy and vibrant garden! For more tree care tips for Iowa gardens, stop by Wallace's today and speak with one of our experts about common tree diseases to be on the lookout for.