Recently, I've received several calls about spraying boxwood to treat preventatively for the boxwood blight. Here is an update of information from NC State researchers:
In the last 3-4 years, Boxwood Blight was officially introduced to this area. It was slow to get going, but is taking off this year with the high rainfall totals we've had in Highlands. Boxwoods growing in shade with poor air movement are at risk more so than those growing in full sun. Like all blights, it is caused by a fungus. These spores can travel by air movement but the most common method of movement is by sticking to a persons clothes, pruning sheers or even vehicles. The most common method of preventing this blight is to be sure pruning sheers are cleaned with bleach prior to trimming. If you use an outside landscape service, I would recommend watching them clean their shears as opposed to taking their word for it! This is critical! The spores are very "sticky" and adhere to just about anything.
Spray all boxwood with 1oz Daconil per gallon of water. Ideally mix the Daconil with 1 oz of Tebuconozole or Propiconazole per gallon of water as well. Tebuconozole is a systemic fungicide (Daconil is a contact fungicide that sticks to the leaves) that will move into the boxwood, through the leaves. It can be purchased at Lowe's or Reeves but it seems hit or miss. Mix these two products (1 oz of each in one gallon of water) into a 1, 2 or 3 gallon pump sprayer- also available at Reeves/ Home Depot/Lowe's and spray the boxwood, covering all leaves to the point of runoff. Ideally, this should be done every 3 weeks. Monthly seems adequate. Treat April-October. Treating through the winter is not necessary.
These are the 2 products that should be sprayed (combined in the same tank) at 1oz/gal water each. These photographs were taken off of Lowe's website.
