Boxwoods are ornamental shrubs found throughout the U.S. They’re popular because they stay green year round and don’t appeal to deer. Alarmingly, a new species of boxwood blight (the fungus Cylindrocladium buxicola) was discovered in the U.S. and several other countries in late 2011. While it is indistinguishable from two other types of relatively benign boxwood blight, this third species is aggressive and deadly, and it threatens to remove all boxwoods from our landscapes unless contained.
There is currently no remedy for the Cylindrocladium fungus, except extreme heat—daily temperatures above 95 degrees Fahrenheit will slow it down or kill it. Fungicides have no effect. The US Department of Agriculture has allocated more than $500,000 for research to cure boxwood blight. Until a remedy is found, homeowners can slow the spread of the disease by detecting it early and using proper eradication procedures. Early detection is especially important since the fungus life cycle can be as swift as seven days from infection to propagating new spores.
Early signs of Cylindrocladium infection are round, brown spots on leaves or lesions on the leaf tip. In advanced stages, leaves drop off and the bare branches show black cankers.
If you have boxwoods on your property, inspect them regularly during the growing season—at least once a week. If your boxwoods show any signs of distress, you should take the following steps:
- Contact the county agricultural extension center for testing. Testing is important since all boxwood blight species look alike. If tests confirm that Cylindrocladium is the culprit, begin removing diseased plants immediately and notify the association manager or a board member as soon as possible.
- Always wear gloves when handling diseased plants, fallen leaves and plant debris. Be careful not to touch healthy boxwoods or parts of garden tools that may come in contact with them. Wash the gloves and tools thoroughly or use disposable gloves.
- Remove infected plants and dead leaves carefully and thoroughly. Fungus on fallen leaves can survive for as long as five years, so removing all debris is essential. Double bag all debris and seal the bags or, if possible, burn or bury diseased plants and debris. Do not combine infected plant debris with other yard waste for pickup or disposal, and do not use it in compost systems.
- After removing infected plants, vacuum porches, decks, walkways, flagstones and other hard surfaces adjacent to diseased boxwoods.
- Replace your diseased boxwoods with alternative plants for the five years following a Cylindrocladium infection. Ask your landscaper or nursery staff for substitutes that are not in the boxwood family. If you opt for new boxwoods, plant them as far from the infected areas as possible.