Boxwoods are a beloved staple in Windsor and Essex County, adding year-round structure and beauty to our landscapes. But when your once-vibrant boxwood starts to look unwell, it can be alarming. Is it a pest? A disease? Or just stress from our unpredictable Southern Ontario weather? At The Spider Guys, we know it can be tricky to tell. This guide will help you become a boxwood detective, identifying common issues and understanding potential treatments.
Is it Pests, Disease, or Stress?
Often, homeowners jump to the conclusion of a pest infestation when their boxwood looks unhealthy. While pests like boxwood worms, boxwood mites, boxwood scale, and the boxwood psyllid are certainly threats in our region, it’s important to consider other factors. Environmental stress, such as harsh winters, drought, or even overwatering, can also lead to symptoms that mimic pest or disease problems. Fungal diseases like boxwood blight are also becoming more prevalent in Southern Ontario and can cause rapid decline.
Spotting the Signs of Common Boxwood Pests:
Knowing the specific symptoms of common boxwood pests is the first step towards effective treatment.
- Yellowing, Cupped, or Blistered Leaves: This is a classic sign of boxwood leafminer activity. If you hold an affected leaf up to the light, you might even see the tiny larvae wriggling inside. Boxwood psyllid infestations also cause distinctive cupping of new growth, often with a white, waxy residue inside.
- Stippling or Bronzing Foliage: This speckled appearance, often accompanied by a dull or dusty look, strongly suggests boxwood spider mites. Look closely at the undersides of the leaves for these minuscule pests, especially during hot, dry periods.
- Thinning Foliage and Webbing: If you notice significant leaf loss and silken threads around the branches, particularly with green or yellowish-green droppings (frass), the culprit is likely the boxwood worm, the larva of the Box Tree Moth. This pest can defoliate a boxwood very quickly. (For more on this destructive pest, see our blog: Protect Your Southern Ontario Boxwoods: Identifying and Managing Common Pests)
- White, Waxy Residue or Small Bumps on Stems and Leaves: This often indicates a scale insect infestation, such as boxwood scale. These small, armored pests attach themselves to the plant and suck its sap.
Recognizing Signs of Disease and Stress:
While this blog focuses on diagnosis for pest issues, here are a few quick indicators that your boxwood’s problems might stem from disease or environmental factors:
- Dark Leaf Spots or Blight: Rapid browning or blackening of leaves, sometimes with black streaks on the stems, can be a sign of fungal diseases like boxwood blight.
- Overall Yellowing or Browning, Especially in Winter: This could be due to winter burn (desiccation from cold winds and sun) or nutrient deficiencies.
- Wilting or Drooping: Can indicate root problems due to overwatering or underwatering.
What to Do Once You’ve Made a Diagnosis:
Once you have a likely culprit, you can consider appropriate treatment options.
- For Box Tree Moth (Boxwood Worms): For small infestations, handpicking caterpillars and removing webbing can help. Biological insecticides like BtK can be effective against young larvae. For larger infestations, professional boxwood spray treatments are often necessary.
- For Boxwood Leafminer: Pruning infested leaves in late winter before adult flies emerge can reduce populations. Horticultural oil applied at the correct time can also target larvae. Systemic insecticides offer more thorough control.
- For Boxwood Psyllid: Pruning affected tips is often sufficient for light infestations. A strong spray of water or applications of insecticidal soap or horticultural oil can also help.
- For Boxwood Spider Mites: Increase humidity around the plant by regularly spraying with water. Horticultural oil or insecticidal soap can be effective, but multiple applications are usually needed, ensuring good coverage of leaf undersides.
- For Boxwood Scale: Horticultural oil applied during the crawler stage (typically late spring/early summer) is a common treatment. Pruning heavily infested branches can also help.
When to Call The Spider Guys for Your Boxwood:
Accurately diagnosing boxwood problems can be challenging, and effective treatment often requires specific timing and products. Contact The Spider Guys for expert assistance if you notice:
- Rapid decline or significant damage.
- Difficulty in identifying the specific pest or problem.
- Large or established infestations that are beyond DIY control.
- You prefer professional pest control in Windsor with targeted boxwood spray applications for peace of mind and guaranteed results.
Protecting your boxwoods is our priority. By being vigilant and knowing the signs, you can take the necessary steps to keep these landscape staples healthy and thriving. If you’re unsure or need professional help, don’t hesitate to reach out to us for expert diagnosis and treatment. For a proactive approach to protecting your boxwoods throughout the year, be sure to read our blog: A Seasonal Boxwood Protection Plan.
Protecting your boxwoods is our priority. At The Spider Guys, we are committed to helping you keep your Southern Ontario landscape healthy and beautiful. If you suspect a pest infestation on your boxwoods, don’t hesitate to contact us for expert identification and effective management solutions. We have the knowledge, experience, and tools to protect your valuable plants. For more expert advice, explore our other blog posts on boxwood pests.