It has now been a full ten age since a mysterious disease affecting 10,000 containerized boxwood ( Buxusspp . and cvs . , Zones 5–9 ) bush in North Carolina and over 100,000 boxwoods in Connecticut was find . Since then , the disease has scatter to all regions of the United States where box is grown . Along the elbow room , we have learned a quite a little about the infamous disease now love as boxwood blight . However , despite great progression in management and education , I frequently happen confusedness and misidentification of the disease . Taking a closer look at this curse of many landscapes will help you decent greet the disease and understand your direction options .
Where did it come from?
Boxwood blight is thought to have initiate in easterly Asia and was circumstantially introduced through the ornamental nursery barter to the United Kingdom , where the disease was first found in 1994 . Over the next fifteen class , the disease spread across Europe and into westerly Asia , even make its way to New Zealand . Because boxwood is used so oftentimes in decorative gardening , it was only a matter of time until it made its way to the United States ( in 2011 ) .
Two other host plants are susceptible to the disease : sweet box ( Sarcococcaspp . and cvs . , Zones 6–9 ) and pachysandra ( Pachysandraspp . and cvs . , Zones 4–9 ) . Along with boxwood itself , these plants are in the boxwood family , Buxaceae . box blight disease is due to two sister fungal specie , Calonectria pseudonaviculataandC. henricotiae . The former is found worldwide and is creditworthy for all box blight in the United States , while the latter also causes boxwood blight in the UK and some parts of Europe .
Where is it now?
Turkish boxwood blight is now well established in North America and commonly go far in new landscapes incidentally on infected nursery stock . The spores acquire by the fungous disease on infected leaf and stem can be spread by twist - driven rainwater splash . They are also ofttimes spread during maintenance . The spore flummox to habiliment , shoes , and specially prick . outbreak often pass off following bush shearing in summer . American boxwood ( B. sempervirens , Zones 6–8 ) and English Turkish boxwood ( B. sempervirens‘Suffruticosa ’ , Zones 6–8 ) are among the most wide planted shrub in many landscapes , and both are highly susceptible . Weather also plays a significant function in the severity each season , as the formation of spore occur best in high humidness and when temperatures are between 60 and 80 F , so disease spreads fastest during wet , warm periods in summer .
What do we do about it?
box blight was once considered a lethal disease , with full - plant life remotion and abandonment the exclusive option . The good news is that we now have tolerant variety of boxwood and know that although box blight does belt down susceptible shrubs if left unaddressed , it is achievable in some situation . However , management require a many-sided approach , and each situation must be considered independently to count the expense , available option , and likelihood of success .
Cultural management
Take all measure possible to reduce folio wetness , which will greatly reduce spore sprouting and infection . We can not prevent rainfall , of class , but we can take other measures . Plant box in full sun , not under trees or against wall that deflect light for half the sidereal day . Avoid overhead irrigation , and encourage flow of air around the industrial plant . Finally , consider hand - pruning rather than shearing . If shearing must be done , do it early in the time of year . It is likely that over - shearing plays a negative role in boxwood health .
Sanitation
Always take off with clean , clean plant life . Inspect often , ruin infected leaf litter , and cut out infect branches . Be aware that clothes and tools may spread spore , so you will need to sterilize any equipment after use .
Fungicides
chemical substance management can be effective for boxwood blight , but only when combine with a exhaustive cultural direction course of study . A respectable program is intensive and may be expensive , involve foliar applications once every one to two weeks during bill blight time of year in summer and early descent . This may only be advisable for gamey - value plantings .
Plant selection
If replanting is your end , talk with professional boxwood growers about your option for more - resistant boxwood species and cultivars desirable for your hardiness zone . Some of these let in Asiatic cultivar ofB. microphylla(Zones 6–9 ) andB. harlandii(Zones 6–9 ) , and NewGen ™ Independence ® (B.‘SB 108 ’ ) and Freedom ® (B. ‘ SB 300 ’ ) from the NewGen ™ boxwood series ( zone 5–8 ) . at long last , consider invalidate the disease altogether by planting nonhost shrubs . Dwarf cultivars of Japanese Buddy Holly ( Ilex crenataand cvs . , Zones 5–7 ) , native yaupon holly ( I. vomitoriaand cvs . , Zones 7–11 ) , genus Viburnum ( Viburnumspp . and cvs . , Zones 2–9 ) , leucothoe ( Leucothoespp . and cvs . , Zones 5–9 ) , and arborvitae ( Thujaspp . and cvs . , Zones 2–9 ) may provide attractive choice for diversification .
Matthew Borden , DPM , is a plant health adviser specializing in nosology and integrated direction of landscape plant pests and diseases .
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Shearing is often the kiss of death for boxwood.Sticky, cylindrical-shaped spores calledconidia(below) are the cause of a rapidly spreading infection of boxwood blight. The fungus spreads easily and quickly via tools and even clothing.Photo: Bartlett Tree Research Laboratories
Photo: courtesy of Matthew Borden
