Boxwood blight (also known as box blight or boxwood leaf drop) is a disease of boxwoods caused by the fungus Cylindrocladium buxicola (also called C. pseudonaviculatum).
History
editThe first description of boxwood blight was from the United Kingdom in the mid 1990s. In 2002 it was discovered in New Zealand. At that time the cause was identified as a new species of fungus and formally named Cylindrocladium pseudonaviculatum. The fungus causing the disease in the U.K. was later named C. buxicola. These are now known to be the same.[1]
It is found throughout Europe.[2][3]
In October 2011 the blight was found in North Carolina and Connecticut. By January 2012 it had also been identified in Virginia, Maryland, Rhode Island, Massachusetts, Oregon, and British Columbia.[4]
Hosts
editEvery species of Buxus that has been tested has been found to be susceptible to infection, and it is likely that all species are. B. sempervirens (English and American boxwoods) are especially vulnerable.[5]
Symptoms and disease process
editThe blight initially presents as dark or light brown spots or lesions on leaves. The leaves typically turn brown or straw color, then fall off.[6] The stems develop dark brown or black lesions.[7]
It is often fatal to young plants.
The spores are dispersed by wind and rain over short distances. Since they are sticky they are probably also spread by birds, animals, and contaminated clothing and footwear. The commonest mode of transmitting the blight is the introduction of asymptomatic plants, or plants treated with fungicide (which can mask the disease) to areas with uninfected plants.[8] Warm and humid conditions facilitate its spread.[9] The fungus does not need a wound to infect a plant, but it does require high humidity or free water.[10]
The disease can surivive for five years in fallen boxwood leaves.[11]
Prevention and treatment
editThere are a number of steps that can be taken to prevent the spread of the blight[12]
- Inspect new plants and cuttings; only buy from reputable nurseries.
- Isolate them for at least one month, longer if psssible.
- Avoid overhead watering.
- Don't work with wet boxwoods.
- Never compost infected material.
- If you see an infected plant:
- Remove the whole plant and put it in a plastic bag. Do not carry it around uninfected plants.
- Consult with a county agent or other expert to be confirm the diagnosis.
- Consider plants other than boxwood.
There is no known cure. Fungicides may prevent the spread of the disease. To be effective, they must be applied to the entire plant, leaves and stems. This can be difficult because boxwood leaves are very closely spaced.[13]
Since this is a new disease, research is ongoing. The Connecticut Agricultural Experiment Station Plant Disease Information Office maintains up-to-date information.
Notes
edit- ^ Douglas. p. 1
- ^ Douglas pp. 1–2
- ^ Milius
- ^ Milius
- ^ Douglas, p. 2
- ^ Douglas, p. 2
- ^ Milius quotes Lynn R. Batdorf, curator of the National Arboretum's boxwood collection (currently not infected): “I’ve never poured diesel fuel on a boxwood, but if I did, that’s what it would look like.”
- ^ Douglas, p. 6, calls this "Trojan horse " or "Typhoid Mary" transmission.
- ^ Douglas, p. 5
- ^ Douglas, p. 6
- ^ Douglas, p. 7
- ^ Douglas, pp. 8–9
- ^ Douglas, p. 9 has details on various fungicides
References
editDouglas, Sharon M. (December 2011). "Boxwood Blight - a new Disease for Connecticut and the U.S." (PDF). Connecticut Agricultural Experiment Station. Retrieved May 26, 2012. {{cite web}}: External link in |publisher=
Milius, Susan (January 20, 2012). "Boxwood Blight Invades North America". Science News. Retrieved May 26, 20. {{cite web}}: Check date values in: |accessdate= (help)