What you need to know about Boxwood blight(calonectria pseduonaviculata)

Boxwoods are beloved for their evergreen charm and ability to create beautifully manicured hedges and borders. But in recent years, a serious disease called boxwood blight, caused by the fungus Calonectria pseudonaviculata, has threatened these landscape staples across the U.S.

What Is Boxwood Blight?

Boxwood blight is a fungal disease that affects boxwood plants, along with some closely related species like pachysandra and sweet box. First identified in the U.S. in 2011, it spreads rapidly in warm, humid conditions and can devastate a landscape if left unchecked.

Symptoms to Watch For

If you have boxwoods in your landscape, here are the main signs to look out for:

• Leaf spots: Circular, tan spots with dark margins that often lead to rapid defoliation.

• Black streaks on stems: Thin black lines along green stems are a telltale early sign.

• Leaf drop: Infected plants lose their leaves quickly, leaving bare branches.

• Rapid decline: Infected boxwoods can go from healthy to unsightly in just a few weeks during active outbreaks.

How It Spreads

Boxwood blight is highly contagious and spreads through:

• Infected plants and cuttings

• Contaminated tools, gloves, clothing, or equipment

• Water splashing spores from plant to plant

• Fallen leaves or debris left around the plant base

Even one infected plant can spread the disease to an entire hedge, especially if conditions are wet and warm.

How to Prevent and Manage It

There’s currently no cure for boxwood blight, but you can take steps to reduce the risk:

1. Plant Resistance Varieties or Alternatives

Some boxwood varieties show greater resistance to blight. Consider using cultivars like:

• Buxus microphylla ‘Wintergreen’ or ‘Green Beauty’

• Buxus sempervirens ‘Vardar Valley’ (moderately resistant)

• Ilex x meserveae ‘Steeds’ is a great alternative for a pyramidal shrub similiar to ‘Green Mountain’
• Ilex Vomitoria ‘Nana’ makes is great for clipped hedging just like boxwood.

2. Sanitize Regularly

Disinfect pruning tools between plants, especially during wet weather. Use a bleach solution or commercial disinfectant.

3. Avoid Overhead Watering

Water at the base of the plant to keep foliage dry and discourage fungal growth.

4. Mulch and Clean Up

Apply mulch to prevent spore splash and always remove fallen leaves or debris, which can harbor the fungus.

5. Monitor Closely

If you notice signs of infection, act quickly. Remove and bag infected material, and dispose of it in the trash—not in compost.

6. Hire a Professional

A trained lawn care professional can help monitor, prune, and apply appropriate fungicides (preventatively) if needed.

A Word to Homeowners

If you’re thinking about adding boxwoods to your landscape—or if you already have them—it’s more important than ever to stay vigilant. At Weedsie, we’re here to help you protect your investment in a healthy, beautiful yard. We offer inspections, maintenance plans, and disease management/monitoring tailored to your property.