How to Get Rid of Fungus on Arrowwood Viburnum Shrub

Arrowwood viburnum (Viburnum dentatum) is a popular shrub known for its dense foliage and beautiful white flowers. However, like any plant, arrowwood viburnums can sometimes develop fungal diseases that affect their health and appearance. In this article, we’ll explore the most common fungal diseases that impact these shrubs and provide tips for treatment and prevention.

Identifying Fungal Diseases on Arrowwood Viburnum

There are several fungal pathogens that frequently infect arrowwood viburnums. Here are some of the most common:

• Powdery Mildew One of the most prevalent fungal diseases, powdery mildew appears as a white or gray powdery coating on leaves, stems and flowers. It thrives in humid conditions.

• Leaf Spot Fungal leaf spots show up as small, dark lesions on foliage. Common culprits include species of Cercospora, Phyllosticta, and Phoma Leaf spots enlarge over time

• Rust: Rust fungi cause yellow, orange, brown or black raised bumps on leaves. Severe infections cause premature leaf drop.

• Anthracnose: This fungal disease results in blotchy, brown dead areas on leaves and stems. It spreads rapidly during wet weather.

• Cankers: Canker fungi attack twigs, branches and trunks. Cankers start as small sunken lesions but can eventually girdle and kill plant tissues.

Carefully inspect your arrowwood viburnum frequently to spot any disease symptoms promptly. Early detection and treatment is key!

Cultural Control for Arrowwood Viburnum Fungus

Making some adjustments to your care regimen can help prevent many fungal diseases:

• Avoid overhead watering and instead use drip irrigation focused at the base of plants. This keeps foliage dry.

• Water early in the day so leaves have time to dry out before night falls.

• Space plants properly to allow good air circulation.

• Remove any diseased branches, leaves or debris around plants.

• Clean up and dispose of all fallen leaves in autumn to remove overwintering spores.

• Prune interior branches to open up air flow and light penetration within the shrub.

• Use mulch to prevent soil from splashing onto leaves during watering or rain.

• Avoid high nitrogen fertilizers that cause fast, succulent growth.

By promoting dry conditions and plant health, you make it much tougher for fungal pathogens to establish themselves.

Fungicide Treatment for Arrowwood Viburnum

If cultural controls fail to protect arrowwood viburnum from fungal attack, fungicide sprays provide another line of defense.

• Broad-spectrum, protective fungicides such as chlorothalonil, myclobutanil, propiconazole, or copper sulfate can be applied every 7-14 days as a preventative measure during damp seasons. Always follow label directions carefully!
• For treating active infections, choose systemic fungicides that penetrate inside plant tissues. Tebuconazole, trifloxystrobin, and fenbuconazole work well against viburnum fungi.
• Organic options like neem oil or sulfur also help suppress fungal diseases. For powdery mildew, use bicarbonate products.
• Rotate between fungicide classes to avoid resistance development. Mixing a protectant with a systemic can improve efficacy.
• Spray thoroughly to coat all leaf surfaces, upper and lower. Get good coverage on stems and buds as well.
• Re-apply every 7-14 days initially, then extendinterval as conditions improve.

With vigilance and prompt treatment, you can successfully combat fungal diseases on arrowwood viburnum. Don’t allow fungus to take hold – a vigorous shrub starts with disease prevention!

How to Prevent Fungal Diseases on Arrowwood Viburnum

Beyond control methods, you can take some key steps to stop fungal diseases from ever gaining a foothold in your arrowwood viburnum shrubs:

Choose Disease-Resistant Cultivars

When selecting arrowwood viburnum varieties, look for ones specifically cited as having enhanced disease resistance, such as:

• Autumn Jazz® – Has resistance to bacterial leaf spot
• Cardinal Candy® – Resists leaf spot
• MohawkTM – Less susceptible to powdery mildew

Starting with genetically superior cultivars gives your plants an advantage against fungal infection.

Ensure Proper Siting

Arrowwood viburnums perform best in full sun. Allow for good spacing between plants and avoid cramming them into shady, enclosed areas with poor air movement.

Well-draining soil is also important. Avoid wet, poorly draining sites. Fungi thrive in continual moisture.

Promote Overall Vigor

A healthy, vigorous arrowwood viburnum is less vulnerable to fungal attack. Use these tips to nurture robust shrubs:

• Plant into well-prepared, amended soil to encourage good root establishment.

• Water thoroughly during dry periods, especially the first year.

• Apply a balanced, slow-release fertilizer each spring. Don’t overdo nitrogen.

• Prune lightly to shape plants and improve air circulation.

• Monitor for pests like aphids that can weaken plants and make them fungus-prone.

Taking a proactive approach focused on prevention is truly the best medicine when it comes to fungal diseases on arrowwood viburnum. But even with great care, problems can sometimes develop. By knowing what to watch for and responding promptly, you can keep your shrubs looking their best for years to come.