Fighting New Blight on Boxwood


2013 to 2015


A working group of applied and basic researchers has been established to coordinate research and extension regarding a highly damaging new disease of boxwood. University and USDA-ARS workers studying disease management and epidemiology, pathogen survival and genetics are collaborating closely to develop a highly focused effort resulting in new information and its dissemination.


A new blight of boxwood caused by the fungus Calonectria pseudonaviculata (synonyms: Cylindrocladium pseudonaviculatum and C. buxicola) has been appearing in southeastern NY landscapes since early 2012, causing leaf spotting and defoliation. This disease was new to the world in 1994, when it first appeared in the UK, and first noted in the US in fall, 2011. New York State horticultural inspectors have also found diseased boxwood at retail establishments, and it is obvious that it is being disseminated through the nursery trade. The NY green industry has asked for help with avoiding infection and dealing with outbreaks, including learning how to safely dispose of infected plant material. Public and private gardeners are very concerned about the disease, as boxwood is one of the few evergreens with low likelihood of deer browse. Interest in deer-proof boxwood alternatives is high, in view of the new disease threat.


A boxwood blight advisory group comprised of members from landscape and nursery firms was established on Long Island in fall 2013 to assist with educational efforts of Cornell University and Cornell University Cooperative Extension of Suffolk Country. Three fact sheets were developed to help educate various audiences about this new problem—see Frequently Asked Questions: Boxwood Blight will help landscapers, nurserymen and arborists inform their customers. Alternatives to Boxwood Blight provides helpful details on plants that most resemble boxwood. Boxwood Blight: Recommended Disposal Practices of Infected Shrubs addresses the needs of those who are concerned that they dispose of diseased plants safely, so that diseased boxwood will not be returned to landscapes as mulch. The fact sheets will be distributed at industry meetings in 2014, and are also available for downloading at the Commercial Nursery and Landscape Program website given above. An article on boxwood blight was also distributed in the Cornell University newsletter Branching Out, and one in The Herbarist, the journal of The American Herb Society. Presentations on boxwood blight and alternatives to boxwood were given at the following meetings in 2013: Nursery Session of the Long Island Ag Forum, Long Island Horticulture Conference, Long Island Horticultural Research & Extension Center Plant Science Day, Society of American Florists Pest and Production Management Conference, NY Arborists Conference, Brooklyn Landscape Gardeners Symposium, Southampton Garden Club, Herb Society of America-LI Chapter, Nursery/Floriculture Disease Management Symposium-Univ. of CA Cooperative Extension, NY State Turf and Landscape Assn., Hudson Valley Nursery & Greenhouse Growers School, Garden Conservancy Rocky Hills Lecture Series, the LI Horticulture Society and the Cornell University Cooperative Extension of Suffolk Fall Gardening Symposium. We have also initiated research into the relative disease susceptibility of cultivars and species of boxwood, and are currently propagating 42 selections from the US National Arboretum collection that will be used in a field trial.


Through our NY educational outreach programming, over 2000 individuals were directly addressed on topics related to boxwood blight during the year. Growers, retailers, gardeners and landscapers have benefited from the educational program. They have learned how to avoid the new disease, and how to recognize it when it occurs. By providing information to landscapers and transfer facilities, we have aimed to prevent the use of diseased boxwood as mulch, which would further spread the disease. Farm Bill funding has been obtained for a multi-state group of researchers (including Cornell University), with the support of the American Nursery and Landscape Association. It is hoped that the research and extension activities, taken together, are reducing plant losses and preserving the long-term use of this valuable ornamental that contributes so significantly to NY landscapes. New York boxwood plantings are worth millions of dollars, and the nursery industry in southeastern NY would like to preserve the profitability of this popular crop.

Submitted by: 

  • Daughtrey, Margery L

Researchers involved: 

  • Daughtrey, Margery L
  • Vescera, Mina
  • Palmer, Cristi
  • Douglas, Sharon
  • LaMondia, James
  • Marra, Robert
  • Kelly , Ivors
  • Benson, Michael
  • Chuan, Hong
  • Nina, Shishkoff
  • Crouch, Jo A

Organizations involved: 

  • IR-4 Project
  • Cornell Cooperative Extension of Suffolk County
  • Rutgers University
  • US National Arboretum
  • Virginia Polytechnic Institute and State University

International focus: 

  • Belgium
  • Georgia
  • Germany
  • New Zealand
  • United Kingdom
  • United States of America

United States focus: 

  • Connecticut
  • Delaware
  • Maryland
  • Massachusetts
  • New Jersey
  • New York
  • North Carolina
  • Ohio
  • Oregon
  • Pennsylvania
  • Rhode Island
  • Virginia

New York State focus: 

  • Delaware