Jason Fulton often hears it from his customers at May’s Greenhouse – their boxwood bushes have the blight. Yet he and other gardening experts say that’s most likely not true.
Extreme cold weather conditions from the past couple years are the more probable culprit.
“Just let them [boxwoods] grow out of it,” he said. “Or I can show them another evergreen they may want to try.”
May’s Greenhouse offers inkberries and hollies as replacements. Newer varieties of boxwoods, such as NewGen boxwoods, are also more disease-resistant. They became available for purchase last year.
“Just stay away from the older varieties of boxwoods,” he said. “Most of my suppliers have already done away with them.”
Fulton said the NewGen boxwoods have suffered some damage from the cold weather this spring, but it is still too early to tell how they respond to other potential diseases.
“Keeping space while they’re irrigated mitigates a lot of problems,” he said.
Boxwood blight is a fungal disease that produces dark spots on leaves and narrow black streaks on the branches. Freezing temperatures can produce similar symptoms, such as dried out and brown-spotted leaves.
The blight was first reported in the United Kingdom in the 1990s and has spread to boxwoods around the world and in approximately 20 states in the United States. The first case of boxwood blight was found in Indiana in 2018.
Richard Beckort, extension educator for agriculture and natural resources at Purdue University, said the disease can spread from plant to plant through moisture. Boxwoods are more susceptible to contracting the blight when it is raining, when the temperature is above 60 degrees and when it is humid. The blight can also spread if your Christmas wreaths and garlands are made of boxwood and are carrying the disease. Pachysandra bushes are also carriers of the blight.
"Browning of the leaves, that dieback of twigs, are exactly the same symptoms as boxwood blight,” he said. "There's another group of fungus diseases that have been around for a number of years that are fairly common on boxwoods that cause browning leaves, twig dieback. So, it's very hard visually to tell the difference exactly of what is boxwood blight.”
Some boxwoods may not even show symptoms of the blight if they are well taken care of. If you think your boxwood bush has the blight, you can apply fungicides to keep it healthy, clean out the sick branches or replace it. Beckort said you should not replace a potentially sick boxwood with another one because the disease can still live and spread in the soil for over five years.
“Pruning out the damaged part; that includes any leaf drop,” he said. “Sanitation is key, so those leaves aren’t there to reinoculate the plant again.”
Available replacements include hollies, cedars, evergreens and junipers. Beckort recommends that homeowners water and fertilize their landscape to keep it healthy.
“Get out there and walk through that landscape; dig through the shrubs, dig through the bushes, look under leaves,” he said. “Do you see insects; do you see signs and symptoms of something starting to get a foothold? It's much easier to control any disease, any insect problem by getting a hold of it early and noticing early and controlling it.”
If you think your boxwood has contracted the blight, you can submit a sample to the Purdue Plant and Pest Diagnostic Laboratory.