I was a novice voluntary at the Piedmont Master Gardeners’Horticultural Help Deskwhen a “ node ” came in , clutching a boxwood branch with brown , desiccated leaves . “ Is this boxwood blight ? ” she need . Yvette , a Help Desk vet , glanced at the sorry - depend twig . “ Do you have dogs ? ” “ Yes , we just adopt two Lhasa apsos , ” the node answer .
Unfortunately , not all boxwood problems are so soft to solve . Many fungous diseases have similar signs and symptoms . Some diseases are merely opportunistic , taking advantage of weakness because of hidden problem . Root legal injury usually manifests as foliage issues . Non - living cause , like road salt and cold weather , can damage foliation as seriously as fungous infections .
This article discusses common disease , pests , and environmental problem facing boxwoods in Virginia . It start with diagnosis and possible treatment . More importantly , it then cover how to prevent these issues from arising in the first place . Finally , this clause covers how to get professional diagnosing and treatment recommendations from the flora disease , nematode , and insect recognition clinic at Virginia Tech .
The main source for this article is theBoxwood Blight Task Forceat the Virginia Cooperative Extension . Never let it be said that we do n’t take boxwood badly in Virginia ! References cite below offer in - profundity descriptions and recommendation .
Boxwood Blight
DiagnosisThe first sign of boxwood blight is brown situation echo with darker brown areas ( see characterisation ) . The smirch are abide by by ( 1 ) sudden defoliation and ( 2 ) black streaks on stems ( see pictures below ) . Fluffy blank cluster of spore may appear , but not always , and they can be difficult to see even if present .
TreatmentThere is no curative for boxwood blight . You might , however , forestall it from spreading to other plants . take away the infected plant entirely . good rake up all fall leaf and twigs . thrust this debris aside , burn it if effectual , or sink it as far from other boxwood as potential . propagate 2 inches of mulch under remaining plants to help prevent spore from splashing up onto foliage . rinse dirt off tools , then disinfect with 70 % ethanol , whitener , or hydrogen hydrogen peroxide ( consult the “ Sanitizers ” subdivision of the Boxwood Blight Task Force site ) . airstream clothes , glove , and footwear with soap and red-hot pee . Finally , consider a preventative fungicide spray on neighboring plants , as described in the “ Fungicides ” part of the Boxwood Blight Task Force website(PDF version).[symple_column size=”one - half ” position=”first ” fade_in=”false ” ]
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[ /symple_column]Prevention
•Avoid introducing blight to your field via septic plant . Only purchase plant fromgrowers that participate ( PDF link)inVirginia ’s Boxwood Blight Cleanliness Program .
•Several boxwood cultivar are tolerant of Turkish boxwood blight , accord to the Virginia Cooperative Extension ( PDF link ) . Note that none are tolerant .
Table 1.Boxwood Blight - Tolerant Cultivars
annul the comply cultivars , which are peculiarly susceptible to blight :
Table 2.Cultivars Quite Susceptible to Boxwood Blight
Other plants in the same family as boxwoods can be hosts for boxwood blight . The most common of these are : Japanese spurge ( Pachysandra terminalis ) , Allegheny spurge ( P. procumbens ) , fragrant spurge ( P. axillaris ) , and sweetbox ( Sarcococcaspecies ) . Try not to grow these industrial plant near your boxwoods .
•Use right cultural practices to boost flora wellness . Healthy boxwoods are less susceptible to blight . Have your soil testedevery 2 - 3 old age and follow the amendment recommendations that fare from the lab . The PMGHorticultural Help Deskscan help interpret these testimonial . Keep antecedent healthy byamending heavy Henry Clay dirt with compostto improve drainage .
Prune boxwood plants to advance airflow , keep leaves dry , and minimize fungous growth . Try not to turn on plants when leave of absence are blotto , which can increase the spread of spore . Avoid overhead irrigation . Mulch under the plants to avoid splashing spore onto leaves . This also economise water supply and deoxidize the pauperism for irrigation in the first position . crease up any fallen leave and branch . Finally , sanitize tools , clothes , and footgear after working on Turkish boxwood .
Other Boxwood Fungal Diseases
•Colletotrichum
DiagnosisDieback of branches without leaf dip , haphazardly distributed around the plant , is the most famed symptom of Colletotrichum ( see photo ) . Black discoloration can be detect under the barque of the idle wood . Sometimes black “ fruiting bodies ” ( the structures that produce spores ) will appear on leaves . Roots will be healthy , that is , they will be brown , and the outer layer will be firmly bond to the core .
TreatmentLike blight , there is no intervention for Colletotrichum . The only surefire way of life to block up it from spreading is to remove and dispose of the septic flora as described above . Thoroughly clean up plant debris and sanitise clothes and tools . There is no preventative atomiser recommended by the Virginia Cooperative Extension .
PreventionAt present , the only urge prophylactic measures are general cultural practices like those described above .
•Volutella :
DiagnosisVolutella also causes dieback without leafage drop . The best way to differentiate Volutella from Colletotrichum is by looking at the fruit body : Volutella ’s are orangish or pink ( see motion picture ) , whereas Colletotrichum ’s are black . For diagnostic purposes , boost fruit bodies to spring up by rate an septic leg in a sealed plastic bag with a few pearl of body of water .
TreatmentThere is no intervention for Volutella , but in general it is not as serious as Colletotrichum . Usually it ’s an opportunistic transmission that designate an underlying issue , such as root problems ( see below ) . Prune infect branches a few inches below the low-down affect leaves and toss out as described above . Clean up plant debris and sanitize pecker , footwear , and clothes . If a plant is seriously taint , remove it completely .
PreventionAs for the above fungal diseases , foreclose Volutella by keep plants salubrious and dry . If there ’s an infected plant nearby , see a preventative fungicide atomizer as distinguish in theVirginia Cooperative Extension Pest Management Guide ( PDF link)(page 4 - 9 in the 2023 guide ) .
•Root waste , e.g. Phytophthora and Pythium ( though technically these two pathogen areoomycetes , not fungus kingdom ):
DiagnosisRoot damage first manifests as subtle yellowing or bronzing of a section of leave . It then shape up to stunt , and finally sectional dieback ( see pictures ) . leave of absence will stay attached . Unlike Colletotrichum , there will be no discoloration under the bark of dying woods . The fibrous root will be blacken and weak , and the kayoed layer will detach easily from the core.[symple_column size=”one - one-half ” position=”first ” fade_in=”false ” ]
[ /symple_column]TreatmentTheVirginia Cooperative Extension Pest Management Guide ( PDF link)(page 4 - 8 in the 2023 guide ) has one testimonial for treating Phytophthora and Pythium etymon putrefaction : potassium common salt of phosphoric , applied as a soil drench or foliar spray . ( take down : these intersection do n’t work as fertilizers , because they contain phosphorous in a dissimilar form than that used by plants . ) Remember , it ’s always better to keep disease than to care for them ( see below ) .
PreventionPrevent root rot by not over - lachrymation plants . When planting Turkish boxwood , avert low - lying arena and poorly drained soil , such as hard stiff . Amend clay with compost to amend drainage . However , do n’t add compost to the hole where the box will be plant ; instead total it to the soil around the planting hole .
Insects , Mites , and Nematodes
•Boxwood psyllid :
DiagnosisLeaf cupping near the end of branches is the signature of box psyllids ( see picture ) . This is noticeable in the saltation , when nymph hatch and start out feed on the plants ’ sap . adult appear in recent springtime or early summer , but they get minimal damage apart from put down egg in bud . Fortunately , boxwood psyllids have only one generation per class .
TreatmentTrim and dispose of feign branches . Insecticides are require only for serious infestations . refer theVirginia Cooperative Extension Pest Management Guide ( PDF link)(page 4 - 52 of 2023 guide ) for more data .
PreventionHalt the life Hz by removing affect branch . Unless there is severe plague , preventative insecticide use is not recommend .
•Boxwood leaf - mineworker :
DiagnosisLook for small yellowish blisters in leaves ( see picture ) where leaf - miner larvae live between the upper and lower tissue stratum .
TreatmentMost infestations can be halted by removing branches with affected leaves . Dispose of the waste as described previously . For severe plague , consult theVirginia Cooperative Extension Pest Management Guide ( PDF link)(page 4 - 49 of 2023 guide ) for more information on insecticide treatments .
PreventionAs for psyllids , forbid succeeding infestations by removing affected leg .
•Mites , primarily boxwood pinch and wanderer mites :
DiagnosisMite damage appears as petite pale dots , term “ stipples , ” on parting . Despite the name , spider mite webbing is apparent only during impenetrable infestations . Heavy feeding can also cause leaf yellowing and end .
TreatmentKnock mites off plant with a strong stream of water . ( This conflicts with the advice to avoid wet leave of absence . Do this only in juiceless conditions , and keep plants well - prune . ) Conventional miticides are not recommended because they can harm beneficial soupcon that eat on harmful mites . Some garden stores and catalog sell beneficial predatory mites , e.g. phytoseiid mites .
PreventionHorticultural oils , applied early in the spring , can kill mite eggs . Consult theVirginia Cooperative Extension Pest Management Guide ( PDF link)(page 4 - 51 of 2023 guide ) for more entropy . Note that horticultural crude oil can harm predatory mites and insects , so only use them if there was a wicked infestation the previous yr .
•Nematodes
DiagnosisNematodes – microscopical worm – flack antecedent , so nematode damage looks like root disease ( see pic above ): leaf yellowing or bronze , stunt , and dieback . As detailed below , the Virginia Tech Nematode Clinic can learn boxwood for harmful roundworm . Root - mile nematode may have nodules to take shape on root word , but in general , nematode terms is hard to distinguish from root disease without using a microscope .
TreatmentThe beneficial treatment is to raise the health of the infected plant with fertilization ( guided by asoil test ) , lachrymation , and pruning . Nematicides are not recommended because they kill good nematode that fertilise on harmful nematodes .
PreventionNematodes can not be eliminated from the environment . avail your Turkish boxwood to campaign off nematode damage by advertize general health as key above . If you are found Modern boxwood , American boxwood are somewhat resistant to nematode damage .
Non - biological Issues
•Water ( too much or too small ):
inordinate watering can promote root rot , as described above . On the other hand , drouth accent can also cause leaves to turn yellow and die . Drought stress is a picky job for freshly planted box , so monitor new plantings cautiously , especially during raging weather . One column inch of rain or irrigation per week is recommended for novel boxwoods . ( This works out to 2.5 quarts per square foot , or 5 gal in a 3 - foot diameter lap . ) lay down boxwood do not need irrigation , except in clip of utmost heating plant and/or drouth .
•Salt
Salt ( e.g. for melting ice ) can exsiccate plants and cause leaf yellowing and/or expiry . If boxwoods near a sidewalk or driveway show this kind of damage , particularly in the outpouring , consider salt as a causa . salinity can harm boxwoods in two ways : through verbatim contact with leave , and by leaching into the dirt .
•Winter / cold-blooded damage
wintertime injury is very vulgar for boxwood . It begins as leaf browning or bronzing in the spring , possibly followed by death of the strike area ( see picture).If the leaf of a boxwood change by reversal dark bolshie or bronze , particularly in the spring , wintertime damage is the potential cause . A good diagnostic for cold injury is that the price only appears on the upper part of a plant , where it is not protected by snow . Simply cut off the affected parts ; the repose of the plant will grow and meet in the missing area .
Avoid wintertime damage by planting box in country protect from wind . northerly and easterly exposure are good than southern or westerly because cold-blooded injury takes spot when frigid plants all of a sudden warm up . Do not fertilize plants in late summer or fall ; this may spur newfangled growing that is not winter - unfearing .
Plant Disease Clinic at Virginia Tech
Needless to say , not all Turkish boxwood problems look like the descriptions and photograph in this article . ThePlant Disease Clinicat Virginia Tech is a fantastic resource for professional diagnosis of plant diseases . Moreover , if the disease clinic suspects that a problem is actually caused byinsectsornematodes , they will send a sample like a shot to Virginia Tech clinics that specialize in those organisms .
Collecting a proper sampleis vital to achieving an exact diagnosis . The clinic will reject insufficient sampling . The optimal sample is a whole plant life , including roots ; be certain to leave a pint of ground around the roots to keep them moist . If a whole industrial plant is n’t feasible , the sample should include branches or twig ( more than one ) that check both live and dead or dying tissue . This avail insure that the disease - causing organism , if there is one , will be actively grow somewhere on the sample . The sample must also let in hempen base in a pint of soil . Read theclinic ’s sampling instructionscarefully before compile a sampling .
“ Digital sample , ” i.e. pictures , are a useful addition to physical samples because they serve the diagnostician analyze the overall health of the plant life and the distribution of any diseased portions . Read the disease clinic’sguide to good digital sample ( PDF link)for top on how to take the most useful pictures .
The cost to send a sample to the Plant Disease Clinic is $ 35 . link yourlocal Virginia Cooperative Extension officefor instructions on where to render sample . In the Albemarle - Charlottesville orbit , get sample to the Horticultural Help Desk in the Virginia Cooperative Extension power at 460 Stagecoach Rd . , Charlottesville . Go to the back entrance of the Albemarle County Office Building off 5thStreet Extended . The help desk is open 9 AM – noon , Monday – Friday from April to October , and Monday / Wednesday / Friday the rest of the year . seek to add samples on Monday to let them to arrive at the clinic before the weekend . Email pictures toalbemarlevcehelpdesk@gmail.com . The Help Desk phone number is 434 - 872 - 4583 .
Closing Thoughts
Boxwoods are popular for many good rationality . Personally , I am very tender of the smell . But boxwood can be difficult to grow , especially in blistering , humid places like Virginia . The ethnical pattern described here will help prevent disease , pestilence ( and pets ) , and the surround from damaging your boxwood . If something does go wrong , hopefully this clause – and thePlant Disease Clinic – will help name and halt any job to get you back on track with beautiful , fragrant box .
References and further reading
have simulacrum : Johannes Bergsma , CC BY - SA 3.0
Agromyzid Leafminers(Virginia Cooperative Extension )
Best Management Practices for Boxwood Blight in the Virginia Home Landscape(Virginia Cooperative Extension )
Boxwood Blight Cleanliness Program(Virginia Department of Agriculture and Consumer Services )
Boxwood Blight Task Force(Virginia Cooperative Extension )
Boxwood Diseases and Insect Pests(Clemson Cooperative Extension )
Boxwoods : key and Manage Common Problems(University of Maryland Extension )
Boxwood Psyllid(University of Kentucky )
Boxwood Psyllid Insects on Shrubs(University of Maryland Extension )
Browning of Boxwood : Is it Boxwood Blight?(Michigan State University Extension )
Home Grounds and creature 2023 Pest Management Guide ( PDF link)(Virginia Cooperative Extension )
Plant Health Alert : meliorate Clay Soils for Better Gardens(Henderson County Center , North Carolina Cooperative Extension )
Reddish - brown Boxwood Leaves unremarkably due to Winter(University of Georgia Extension )
Spider Mites on Trees and Shrubs(University of Maryland Extension )
Types of Boxwood(New York Botanic Garden )
Virginia Tech Plant Disease Clinic
Virginia Tech Soil Testing Laboratory
Volutella Stem and Leaf Blight on Boxwoods(University of Missouri )
