Boxwood tips are used in holiday decorations, including wreaths. Carefully inspect wreaths in stores and garden centers before buying. Leaves and twigs may be infected with the boxwood blight fungus, and could be a source of infection for residential boxwood in Delaware. Conditions of wet weather and high humidity have been favorable for boxwood blight in the Mid-Atlantic, where the serious blight has been confirmed. The fungus Calonectria pseudonaviculata causes severe defoliation and death of container boxwoods, and dieback of in-ground plantings. Most boxwood species are susceptible, including American and English boxwood (Buxus sempervirens), little leaf
boxwood (B. microphylla) and hybrids such as B. sinica. Timely and accurate identification by microscopy is important for management of this aggressive disease. If you suspect a wreath or decorative piece is infected with boxwood blight, dispose of it in a bag in the trash, do not compost or discard near foundation plantings of boxwood. Spores would be dormant at this time, but management consists of strict sanitation along with a diligent fungicide schedule over a couple of seasons.
N Gregory Dec 12, 2018
Tag: boxwood
Boxwood Blight in DE MD PA NJ
Conditions of wet weather and high humidity have been very favorable for boxwood blight in the Mid-Atlantic region, where states have confirmed boxwood with the serious blight. The fungus Calonectria pseudonaviculata causes severe defoliation and death of container boxwoods, and dieback of in-ground plantings.
Most boxwood species are susceptible, including American and English boxwood (Buxus sempervirens), little leaf boxwood (B. microphylla) and hybrids such as B. sinica. Pachysandra is a host, and can be a source of spores causing new infections. Sweetbox (Sarcococca) has been identified as a host. Other diseases affect boxwood, and environmental stress plays a role in predisposition to disease. 
Timely and accurate identification by microscopy is important for management of this aggressive disease. Sanitation is extremely important in management. Contact DE Dept of Ag or the UD Plant Diagnostic Clinic if you suspect boxwood blight.
NFG 9/28/2018
Weather Woes and Plant Diseases
Cloudy, wet, damp, cool and dreary are words that have been heard over and over recently, regarding the weather in Delaware. Cloudy and damp weather is conducive to plant pathogens that infect in the spring. Fungi and bacteria overwinter in twigs and buds of trees and shrubs. Spring rains and humidity will prompt new growth and spore production, and then winds and rains carry spores to newly emerging flowers and leaves. Recent weather has favored plant disease, but we have also had injury from freezing weather that occurred in April. Hydrangea has been reported with browning and dieback, and samples have come into the Plant Diagnostic Clinic. New growth came out early due to warm weather, and growth of buds and leaves has been affected by the freezes that we had in the area April 5, 6, and 10th. Plants will put out new growth when the weather warms again. Affected growth could be pruned back, depending on the type of
hydrangea, and whether it blooms on new wood or old. Frost or freeze damage has also been observed on new growth of boxwood, and other shrubs. These plants should put out new growth when the weather warms. Fruit trees that were affected by frost and freeze will have fewer fruits this season. Keep up fruit tree sprays. Fungicide sprays should also be going on Douglas fir and spruce that are affected by needlecast fungi. Fungicide applications should be made when new needles are ¼ inch long, followed by a second application ten days later. Check annuals carefully for Botrytis blight or grey mold, and prune or discard plants. Sanitation is a big part of plant disease management.
N. Gregory 5/6/16
Management of Boxwood Blight in the Landscape
MANAGEMENT OF BOXWOOD BLIGHT (caused by the fungal pathogen Cylindrocladium pseudonaviculatum) will be important in our area over the next few years, after detections in MD, DE, and PA. Be cautious when bringing new boxwood plants into a site with established boxwood. A nursery quarantine or watch area may be a wise thing for landscapers to set up, putting plants on a watch for 4 to 5 weeks before installing in a landscape planting.
Dr. Karen Rane, diagnostician with University of MD, spoke with Dr. Jim LaMondia from the Connecticut Ag Experiment Station and Dr. Kelly Ivors from North Carolina State University recently, regarding management in a landscape with mature boxwoods. They emphasized that, if all infected boxwoods are not going to be completely removed and destroyed, then pruning out and destruction on-site of all infected branches is necessary to reduce inoculum. Just a few fallen leaves will serve as an important inoculum source. Dr. Ivors said that nurseries in NC use a flamer (used for weed management in organic systems) to destroy fallen leaves on the soil surface after plants have been removed. Vacuuming hard surfaces using a shopvac can also help to remove fallen leaves. Drip irrigation system instead of overhead can be important in management. Wetting of foliage promotes splash dispersal of spores as well as providing the optimum environment for spore germination and infection. Sanitation and fungicide applications will be extremely important for a few years to control boxwood blight. One year of management will not be enough, because microsclerotia in fallen leaves can survive for several years, and serve as a source to cause infections if new growth is not protected.
Dr. LaMondia and Dr. Ivors emphasized the use of protectant and systemic fungicides in combination to help protect new growth from disease and to reduce sporulation. A spray that includes chlorothalonil should be applied a day or two prior to pruning out diseased material in order to kill spores on the surface of the infected tissue, or soon after pruning. Both researchers recommended using combination sprays containing both a protectant and a systemic fungicide either as a tank mix of two products with different modes of action or using a pre-mixed product that contains two active ingredients. Both suggested chlorothalonil as the best protectant product. Fungicides sprays should be alternated every 2 weeks when conditions are favorable for disease, as one or two sprays in a growing season will not control boxwood blight. Dr. LaMondia suggested starting with a tank mix of thiophanate-methyl +chlorothalonil, followed two weeks later with a propiconazole + fludiozinil (Medallion) spray. Dr. Ivors suggested alternating Palladium (fludioxinil and cyprodinil) and Spectro (thiophanate methyl and chlorothalonil). The addition of a spreader sticker may be necessary to improve coverage but check individual product labels. Products should be applied by a certified professional with the proper equipment for coverage of large plants, according to the fungicide label. Please see the following web site for some chemical recommendations and rates: http://www.anla.org/docs/government%20relations/boxwood%20blight/7.22.13-BB.pdf
NFG 9/3/13
Boxwood Blight Confirmed in Delaware
Boxwood blight caused by the fungus Cylindrocladium pseudonaviculatum was confirmed in a retail nursery in Delaware on June 19, 2013.
Boxwood blight was first identified in the U.K. in 1994 and then in the U.S. in October of 2011. The disease has been identified in nurseries and landscapes on boxwood and pachysandra. It has been confirmed in NC, CT, VA, RI, MD, MA, OR, NY, PA, OH, and Delaware. It was identified in the UD Plant Diagnostic Clinic in 2012, but came from plants in Maryland. In June of 2013, boxwood blight was identified in a retail nursery in Delaware.
See the new fact sheet from University of Delaware Cooperative Extension at: http://extension.udel.edu/factsheet/boxwood-blight-caused-by-the-fungus-cylindrocladium-pseudonaviculatum/
See the links below from American Nursery and Landscape Association and Connecticut Agricultural Expt Station:
http://www.ct.gov/caes/cwp/view.asp?a=3756&q=500388