Boxwood Blight Disease

Boxwood Blight Disease
The purpose of this training is to provide you with an understanding of the significance of boxwood blight, become confident in recognizing the symptoms associated with the disease, and gain an understanding of the best management strategies we have available right now for controlling the disease and preventing its spread. As this disease may spread, it is important that we train others to recognize it to help ensure early detection if it is introduced into new areas. The text provided in the notes section is not meant to be read verbatim to the audience. It is meant to provide the speaker with the necessary background information to support what is presented on each slide. Photo credit: Mary Ann Hansen, Virginia Polytechnic Institute and State University, bugwood.org #

Introduction Boxwood blight is a fungal disease of Buxus sp.
First reported in the United Kingdom in the 1990s First detected in the U.S. in North Carolina and Connecticut in 2011 Also called box blight, boxwood leaf drop and Cylindrocladium box blight Boxwoods (Buxus sp.) are one of the most commercially important evergreen ornamental shrubs. They are widely planted in the landscape because of their ability to be shaped into forms and their resistance to being eaten by deer. They are often used in topiary gardens in residential and commercial landscapes and at many U.S. historic sites including the White House and Monticello. The annual market value of boxwood is estimated to be over $103 million in the United States alone. Boxwood blight is a fungal disease of boxwood species. This disease is also known as box blight, boxwood leaf drop and Cylindrocladium box blight. The causal agent is the fungus Calonectria pseudonaviculata (syn. Cylindrocladium pseudonaviculatum, Cy. buxicola). Symptoms of boxwood blight include leaf spots, rapid defoliation, distinctive black cankers on stems, severe dieback, and death of the plant. Boxwood blight was first reported in the United Kingdom in the mid 1990s, followed by reports in New Zealand in This disease has since spread throughout Europe. Boxwood blight was listed in the European Plant Protection Organization (EPPO) Alert in 2004 but was removed in 2008 because no international action was requested in response to this disease. However, this disease is still considered a great threat to boxwoods in the ornamental industry in Europe. Boxwood blight was detected in October 2011 in North Carolina and Connecticut. Since the initial detection, this fungal disease has spread to many other states. Information sources: 4) 8) 10) 19) 24) Damage of boxwood blight Photo credit: Kelly Ivors, NSCU, Dept. of Plant Pathology

Distribution of Boxwood Blight Disease
No sampling Sampled but not found Intercepted or detected, but not established Under eradication Considered established in parts of the sate Boxwood blight was first reported in the United Kingdom in the middle of 1990s, followed by New Zealand in Since the first reports, this disease has spread throughout Europe including Austria, Belgium, Croatia, Czech Republic, Denmark, France, Georgia, Germany, Ireland, Italy, the Netherlands, Norway, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. Iran is the only country reporting the disease in Asia. In the United States, the disease was first reported in October 2011 in North Carolina and Connecticut. Since the initial detection, this fungal disease has been now reported in 11 additional states in the United States including Delaware, Georgia, Maryland, Massachusetts, New Jersey, New York, Ohio, Oregon, Pennsylvania, Rhode Island and Virginia. The disease has been reported in Canadian provinces including British Columbia, Ontario and Quebec. Although the pathogen appears to be endemic to Central America, the Caribbean, and Mexico, these claims have not been confirmed by scientific research. The origin of the pathogen is not known yet nor is how the pathogen was introduced into the U.S. The pathogen may have been imported with symptomless plants or propagating materials, which can survive well in plant debris and soil. For latest information about Boxwood Blight Disease distribution, see distribution map at Information sources: 4) 19) 20) 23) 24) 31) Map based on NAPIS Pest Tracker - and Malpi-Wight et al. 2014

The Fungal Pathogen Sporodochium with spores and vesicles
This fungal pathogen belongs to the family Nectriaceae. The scientific name of this fungal pathogen is Calonectria pseudonaviculata Crous, J.Z. Groenewald and C.F. Hill. There is a synonym however Cylindrocladium buxicola. When the disease was initially described in the United Kingdom, the pathogen was not identified. In 2002, after the detection of the pathogen in New Zealand, the fungus was described as a new species. In that same year, in Europe however, a new fungal pathogen that also attacked boxwoods was described as Cy. buxicola. Later, these two pathogens were shown to be the same species. The correct scientific name to use is Calonectria pseudonaviculata which is described based on the teleomorph structure. On hosts, this fungus produces spores and fruiting structures called sporodochia which are usually seen on the undersides of infected leaves and in the black lesions on the stems. Huge numbers of spores called conidia are formed in the sporodochia which show the typical crystalline appearance due to the hyaline color. Spores (green arrow) are cylindrical in shape and 42 to 68µm x 4 to 6µm in size. Vesicles (red arrow), the terminal swollen hyphal structure of conidiophore, are also produced in the fruiting structures. The pathogen growth is optimal at 25°C, it cannot grow at over 30°C. This fungal pathogen belongs to the genera Calonectria which contains many other fungal pathogens that affect the cut-flower and ornamental plant industries. For example, Ca. morganii causes blight and wilt of azalea and rhododendron, while Ca. pauciramosa causes disease in many ornamental plants that are grown in pots. Ca. ilicicola causes peg, pod, and root necrosis of peanuts and blight crown and root rot in several other hosts. Information sources: 4) 5) 8) 11) 16) 24) 27) Sporodochium with spores and vesicles Vesicles and cylindrical spores Photo credits: Left and right - Sandra Jensen, Cornell University, bugwood.org # and #

Alternative Life Cycle of the Disease
The pathogen can survive as mycelium in cankers on infected stem tissues and in leaf debris for at least 5 years. The pathogen can produce clamydospores and microsclerotia, long-term survival resting structures, in infected leaf and stem tissues when incubated in a moist chamber. In general, some Cylindrocladium species produce microsclerotia that are hardened spores or mass of hyphal structures in host tissue that can survive as long as 15 years in soil. Although roles of the resting structures are not well understood in field conditions, the boxwood blight pathogen may also persist for a long time in the infected tissues. The resting structures can sporulate under proper environmental conditions. The surviving pathogen can produce spores if the environmental conditions are appropriate and infect susceptible hosts. Those spores then start to attack the hosts. Information sources: 4) 5) 8) 13) 24) 28) Pathogen can overwinter as mycelium in dead leaf material Pathogen can also survive as clamydospores and microsclerotia in infected leaf tissue Spores produced from clamydospores and microsclerotia can then infect other hosts Photo credits: Left - Mary Ann Hansen, Virginia Polytechnic Institute and State University, Bugwood.org, # ; Center – Norman L. Dart, Virginia Department of Agriculture; and Right - Sandra Jensen, Cornell University, bugwood.org #

Signs Fruiting structures containing conidiophores,
As symptoms develop on the leaves and stems, the pathogen produces asexual fruiting bodies called sporodochia. Sporodochia contain conidiophores where a number of stick cylindrical spores and terminal vesicles are formed under high humidity and warm temperature conditions. Sporodochia produced by boxwood blight are unique due to their white color (which are visible with a hand lens) which makes them an important sign to look for when scouting for boxwood blight. Information sources: 5) 8) 25) Fruiting structures containing conidiophores, conidia and vesicles developing on a leaf spot Fruiting structures containing conidiophores, conidia and vesicles developing on black streaks Photo credit: Left and Right – Sandra Jensen, Cornell University, Bugwood.org # and #

Life Cycle of the Disease
Spores (conidia) disperse through water (such as rainfall or watering) as well as wind to infect boxwood leaves. Germination occurs 3 hours after inoculation. The pathogen produces germ tubes which enter through the stomata or can directly penetrate through the cuticle in 5 hours without forming an appressorium (a specialized organ of many fungal pathogens used for infection). The pathogen colonizes the host tissues intercellularly and conidiophores are produced on the leaf surface after 7 days. Spores and vesicles are produced on conidiophores. They are aggregated and develop into white asexual fruiting structures called sporodochia which are easily recognized with the naked eye. The spores are then released to infect other healthy hosts. The life cycle of this disease can be completed in one week. For a successful infection, warm (18 to 25°C or 64 to 77°F) and high humid conditions are necessary. Information sources: 4) 5) 8) 24) 25) Spores disperse through water Defoliated boxwood Germination occurs 3 hours after inoculation Conidiophores are produced after 7 days Photo credits: Spore dispersed - Sandra Jensen, Cornell University, bugwood.org # , Colonization of stems - -Mary Ann Hansen, Virginia Polytechnic Institute and State University, bugwood.org # and Kelly Ivors and Mike Munster, NC State; conidiophores - Elizabeth Bush, Virginia Polytechnic Institute and State University, Bugwood.org, # ; defoliated boxwood - Kelly Ivors, NSCU, Dept. of Plant Pathology

Hosts Plants in the Buxaceae family are affected All Buxus spp.
Pachysandra spp. Sarcococca spp. Master file of all known hosts: Other hosts of Calonectria pseudonaviculata Although there are differences in susceptibility between some species and cultivars, all boxwood (Buxus spp.) species are considered susceptible hosts. English boxwood (Buxus sempervirens ‘Suffruticosa’) and American boxwood (B. sempervirens) are highly susceptible while the leathery-leaved B. balearica is the most resistant. Although there is no evidence of infection in the landscape, sweet box (Sarcococca spp.) is also susceptible when artificial inoculation tests are done. Spurge (Pachysandra terminalis), a common groundcover in the boxwood family, and P. procumbens are also considered as susceptible hosts showing small scale symptoms like yellow-haloed and tan leaf spots. Information sources: 5) 7) 8) 12) 16) Little leaf boxwood (B. microphylla) English boxwood (B. sempervirens) Spurge (Pachysandra terminalis) Photo credit: Left – Jerzy Opiola, wikimedia commons, Center - Karan A. Rawlings, University of Georgia, Bugwood.org # , Right – Rob Routledge, Sault College, Bugwood.org #

Initial Symptoms Dark or brown leaf spots Dark or brown lesions
Initial symptoms include dark or light brown spots on the leaf surface and then lesions which coalesce with a concentric pattern or zonate lines (yellow arrow). The initial symptoms quickly progress under warm and humid conditions, resulting in expanded areas of brown leaves. Information sources: 7) 8) 25) Dark or brown leaf spots Dark or brown lesions Photo credits: Kelly Ivors and Mike Munster, NC State

Advanced Symptoms Black streaks on stem Blighted leaves
The pathogen also infects the stem from the soil line to the shoot tips, producing distinctive and diagnostic dark stem cankers or black streaks. Heavily infected boxwood are usually defoliated and the pathogen repeats infection, which causes weakened root function and eventually leads to death of the plant. Advanced symptoms on the leaves includes blight, followed by severe defoliation in a few days. The disease affects all above ground parts of boxwood, but does not seem to infect the roots. Information sources: 5) 7) 8) 25) Black streaks on stem Blighted leaves Defoliated boxwood Photo credits: Mary Ann Hansen, Virginia Polytechnic Institute and State University, bugwood.org # , # , and #

Dispersal The pathogen is spread by rain splash or wind for short distances The pathogen can spread long distances through Movement of infected plant materials Contaminated agricultural tools Worker’s shoes and clothing Animals and birds “Trojan horses” and “Thyphoid Marys” The pathogen spores are dispersed by rain splash or wind for short distances. Long distance spread occurs through the movement of infected plant materials. Humans can move the pathogen as they go from landscape to landscape. In addition, the spores can adhere to shoes, gardening shears, lawn mowers, etc. Because the spores are sticky, it is possible that they can be dispersed via animals and birds. Unintentional spread of this pathogen occurs through the movement of apparently healthy plant material. When conditions are not conducive to disease, plants can harbor the fungus but appear asymptomatic. Some fungicides can suppress the disease but not kill or eradicate the fungus, so plants appear healthy for some time until the fungicide is no longer effective and the pathogen resumes killing the plant. This phenomenon is called the “Trojan horse” or “Typhoid Mary” syndrome. Information sources: 8) 24)

Scouting for Boxwood Blight
Train staff and workers on boxwood blight symptoms Scout all susceptible hosts regularly Suspected plant should be submitted to plant diagnostic lab for identification Managing boxwood blight should be focused on Integrated Pest Management which combines scouting, cultural, and chemical practices. Scouting the crop is important for managing boxwood blight. All staff and workers should be trained to recognize the symptoms of boxwood blight and scout frequently during pathogen favored seasons. Since other genera including Pachysandra spp. and Sarcococca spp. are reported as susceptible hosts, it is important to scout all possible host plants. Once suspected plants are found, they should be submitted to a plant diagnostic lab for confirmation. Information sources: 8) 13) 16)

Cultural Control of Boxwood Blight
Sanitation Disease-free materials Removing infected plant material Disinfect all equipment Adequate planting space Temperature and moisture management No overhead watering Use resistant species of boxwood The most effective control practice is the exclusion of the disease. All infected plant material should be destroyed immediately in order to reduce the further spreading of the pathogen. The removal and destruction of leaf and stem debris is important because the pathogen can survive in the plant material for a long time. All equipment such as pruning shears, worker’s outfits and shoes, and other tools should be sanitized, using ethyl or isopropyl alcohol at 70 to 100%, sodium hypochlorite (10% Clorox), phenolics at concentrations of 0.4 to 5% or quaternary ammonium at concentrations of 0.5 to 1.5%. Disease-free plant materials should be used after careful inspection of symptoms. It is important to leave appropriate space between plants, which helps to circulate the air and reduce conditions favorable for pathogen development. Overhead watering should be avoided because water is critical for the spread and development of the disease. Less susceptible or disease resistant species of boxwood can reduce the potential of the blight disease. Buxus balearica and Sarcococca sp. are reported to have lower rates of infection. Information sources: 8) 17) 25)

Chemical Control of Boxwood Blight
Some fungicides inhibit sporulation and growth of the fungus Fungicides tested include: Chlorothalonil, Fludioxonil, Carbendazim, kresoxim-methyl, a mixture of epoxiconazole + pyraclostrobin, a mixture of boscalid + pyraclostrobin, azoxystrobin, and mancozeb You must check with local extension faculty as recommendations differ from state to state There is no fungicide that kills the pathogen but some fungicides can inhibit sporulation and growth of the pathogen. In the lab, Chlorothalonil and Fludioxonil were reported as a very effective protectants. Carbendazim did not affect fungal spore germination rates, but mycelial growth was inhibited. Mycelial growth was also inhibited by kresoxim-methyl, a mixture of epoxiconazole + pyraclostrobin, and a mixture of boscalid + pyraclostrobin. Other fungicides recommended are azoxystrobin and mancozeb. You must check with your local county agent as fungicide application recommendations and rates differ from state to state as well as on which plants they can be used and at what time of the year. Information sources: 8) 12) 17) 24) 31)

Diseases Similar to Boxwood Blight

Phytophthora Root and Crown Rot
Complex of causal agents Phytophthora cinnamomi, P. nicotianae, P. citrophthora and P. parasitica Phytophthora root rot is one of the most serious diseases of many container and field grown woody ornamentals. The causal agents are water molds which are fungus-like organisms called Oomycetes. The causal agents of Phytophthora root and crown rot, sometimes called Phytophthora blight, on boxwood are related to the complex of Phytophthora nicotianae, P. cinnamomi, P. citrophthora and P. parasitica. Phytophthora spp. belong to a family Pythiacea. Information sources: 8) 18) 21) 24) 26) 32) Asexual spores in Phytophthora spp. Sexual spores in Phytophthora spp. Photo credit: Left – Paul Bachi, University of Kentucky Research and Education Center, Bugwood.org # and Right - Mary Ann Hansen, Virginia Polytechnic Institute and State University, bugwood.org #

Symptoms Leaves light green, yellow and bronze Crown wilt Roots discolored and rotted Bark rotted and peeled at the crown Infected trees show rotten roots, stunting, necrotic bark lesions, leaf chlorosis and crown wilt. Leaves initially appear light green, then turn yellow and bronze in color, extending through the whole crown. Rotten roots are dark brown or black in color, which sometimes extend above soil. Information sources: 18) 26) 32) Damage by P. nicotianae Photo credit: Raj Singh, LSU AgCenter

Management Avoid high soil moisture and poorly drained soil Use of disease-free plants Appropriate fungicides for preventative effects Be sure that trees are planted where the disease has not occurred. It is essential to manage soil water and moisture because the pathogens develop well in poorly drained soil. Be sure to sanitize pots that are to be reused. For chemical control practices, there are fungicides that can be used preventatively against Phytophthora. These chemical should be applied and are most effective when applied prior to establishment of the pathogens in the plant host. Group 4 and Group 33 fungicides are used to manage the causal agent, but do not kill it. They can stop it before it gets to the plant, but will only slow down the growth once the plant is infected. Be sure to rotate fungicides that have a different mode of action to prevent Phytophthora from developing resistance to the management product. Information sources: 1) 21) 32) Damage by Phytophthora root rot Photo credit: William Fountain, University of Kentucky, Bugwood.org #

Phytophthora Root and Crown Rot vs. Boxwood Blight
Phytophthora spp. that cause root and crown rot can be confused with Boxwood blight because of symptoms which include wilting and discoloring of the foliage. However, Phytophthora spp. do not produce sporodochia on the leaves but they do affect the root system. Information sources: 8) 24) Wilting and discoloring of the foliage due to Boxwood Blight Wilting and discoloring of the foliage due to Phytophthora Root and Crown Rot Photo credit: Left – Mary Ann Hansen, Virginia Polytechnic Institute and State University, bugwood.org # ; Right - Elizabeth Bush, Virginia Polytechnic Institute and State University, Bugwood.org, #

Volutella Blight Volutella buxi Also called canker or leaf blight
Pseudonectria rousseliana Also called canker or leaf blight Volutella buxi (sexual stage: Pseudonectria rousseliana) is the causal agent for Volutella blight on boxwood. It is also called canker or leaf blight. The pathogen affects both American and English boxwood. Volutella buxi is in the family Nectriaceae. Information sources: 6) 8) 32) Fruiting bodies Photo credit: Bruce Watt, University of Maine, Bugwood.org, #

Salmon colored sporodochia of Volutella blight
Straw colored leaves Symptoms and signs Poor growth Leaf tip turns red, bronze, straw-tan color Branch dieback Discoloration of wood Salmon-colored fruiting structures; sporodochia Symptoms usually appear in the spring beginning with poor growth. Infected leaves turn red and bronze and then finally a distinctive straw-tan color. Infected branches dieback, revealing loose bark and discoloration of the wood. Salmon-colored fruiting structures of the fungal pathogen are produced on leaves and stems. Information sources: 6) 8) 32) Salmon colored sporodochia of Volutella blight Photo credit: Raj Singh, LSU AgCenter and Elizabeth Bush, Virginia Tech

Volutella Blight Management Removing dead materials
Improve air circulation and light penetration Application of a copper or lime-based fungicides Infected plant material should be removed as soon as possible. Thinning practices are necessary for the plants in order to improve air circulation and light penetration. Copper or lime-based fungicides are effective for preventing the disease, which should be applied after dead leaves and branches are pruned out and before new growth begins in the spring. Information sources: 6) 32) Photo credit: Raj Singh, LSU AgCenter

Volutella Blight vs. Boxwood Blight
Volutella blight caused by Volutella buxi is sometimes confused with boxwood blight due to similar symptoms including straw to tan colored shoots, discoloration of wood underneath, and leaf drop and dieback. However, the main difference is that the Volutella blight pathogen produces pink to orange or salmon-colored sporodochia on infected tissues, while boxwood blight pathogen produces white sporodochia. Information sources: 8) 24) Leaf spots and sporodochia on Boxwood blight Leaf spots and sporodochia on Volutella blight Photo credit: Left – Sandra Jensen, Cornell University, Bugwood.org # and # , Right (leaf spots) – Florida Division of Plant Industry Archive, Bugwood.org # , (sprodochia) – Elizabeth Bush, Virginia Tech

Caused by the fungus Colletotrichum theobromicola
Boxwood Stem Canker Caused by the fungus Colletotrichum theobromicola Boxwood stem canker is caused by the fungus Colletotrichum theobromicola. This species is part of the 22 species and one subspecies of the Colletotrichum gloeosporioides complex. It is broadly distributed in tropical and subtropical regions and has a wide range of hosts. Information sources: 23) 29) Photo credit: Raj Singh, LSU Ag Center

Removal of bark revealing black discoloration
Boxwood Stem Canker Symptoms include light tan to yellow colored foliage that remain attached to the plant. Defoliation seldom occurs. Removal of the bark on infected stems reveal bright black discoloration that may extend to the tip of the stem. Symptoms can be easily confused with Phytophthora root rot. In the case of Boxwood stem canker though, the roots remain healthy. Information sources: 23) Removal of bark revealing black discoloration While the foliage is yellow, yet still attached, the roots remain healthy. Photo credit: Raj Singh, LSU Ag Center

Boxwood Stem Canker Management
Prune dead materials well below the obvious symptoms Disinfect equipment Improve air circulation to dry the foliage faster There is not much information on good management strategies for boxwood stem canker. Good cultural practices to avoid infection and reduce disease or pathogen spread must be incorporated. Disinfection of cutting or pruning tools, discarding the diseased material properly and improving air circulation to promote rapid drying of foliage must be practiced. Information sources: 23)

Boxwood Stem Canker vs. Boxwood Blight
Boxwood stem canker has yellow to tan colored foliage that do not fall off the shrub. There is also black discoloration under the bark. Plants suffering from boxwood blight also have black discoloration, but the yellowed leaves fall off the plant. Information sources: 23) Symptoms of boxwood stem canker Symptoms of boxwood blight Photo credit: boxwood stem canker - Raj Singh, LSU Ag Center; boxwood blight - : S. M. Douglas, CAES, University of Kentucky

Macrophoma Leaf Spot Macrophoma candollei Symptoms: Signs: Management:
Leaves turn yellow or straw-colored and leaf drop Signs: Fruiting structures; black dots on the infected leaves Management: Generally no control needed Marcophoma leaf spot is caused by Macrophoma candollei which is usually a weak fungal pathogen. Typical symptoms are yellowing leaves and leaf drop. Diagnostic signs are black fruiting structures of the pathogen that appear as small dots on the symptomatic leaves. This disease is usually not a serious problem so generally controls are not needed. Macrophoma candollei is in the family Botryosphaeriaceae. Information sources: 8) 15) 32) Fruiting structures on leaf surface Photo credit: Sharon M. Douglas, The Connecticut Agricultural Experiment Station

Macrophoma Leaf Spot vs. Boxwood Blight
Both Macrophoma leaf spot and boxwood blight cause yellowing of the leaves and leaf drop. However, Macrophoma leaf spot has small black fruiting bodies on the symptomatic leaves whereas boxwood blight has white to dull gray sporulation on the undersides of the green leaves. Information sources: 8) 14) Fruiting structures on leaf surface caused by Macrophoma leaf spot White to dull gray sporulation on undersides of green leaves caused by boxwood blight Photo credit: Sharon M. Douglas, The Connecticut Agricultural Experiment Station

Other Disease and Insect Problems on Boxwood

Boxwood Leafminer Monarthropalpus flavus Adults look like mosquitoes
Emerge late April or early May Larvae are found between the tissues of the leaves Adult of boxwood leafminer Boxwood leafminer (Monarthropalpus flavus (Diptera: Cecidomyiidae)) is the most serious insect pest damaging boxwood. Adults are small (3mm or 1/8 of an inch long) and look like orange mosquitoes. They emerge over a period of 10 to 14 days from late April to early May. The length of the emergence period depends on the weather conditions but an individual leafminer only lives around 24 hours. A female lays about 30 eggs. The eggs are white, oval, and tiny (about 0.3mm in length) and laid inside the leaf. It takes 3 weeks for the eggs to hatch. The mature larvae are yellowish white and 2mm or 1/10 of an inch in length. They feed inside tissues of leaves from June through early fall. They overwinter in the leaves and pupate the following April. The pupae are yellowish white in the beginning, turning dark brown shortly before the adults emerge. There is one generation per year. Information sources: 9) 15) 32) Larva of boxwood leafminer Photo credit: Adult - Jim Baker, North Carolina State University, Bugwood.org # , and larva – Clemson University – USDA Cooperative Extension Slide Series, Bugwood. org # UGA

Blister symptoms caused by larvae feeding within the leaves
Boxwood Leafminer Signs include blotchy, puffy mines Symptoms include distorted, yellow or brown splotchy leaves The larvae feed in between the outer surfaces of leaves causing blotch shaped mines which are signs of their presence. Symptoms include distorted, yellow or brown leaves which are seen from late summer through the following spring. They have a blistered-like appearance from late summer through the following spring, but this may not be noticable until late summer. A heavily affected boxwood trees can be killed by serious loss of leaves. Information sources: 15) 32) Blister symptoms caused by larvae feeding within the leaves Photo credit: John A. Weidhass, Virginia Polytechnic Institute and State University, Bugwood.org #UGA

Damage caused by boxwood leafminer to boxwood
Management Insecticides Malathion and Carbaryl for adults hovering Acephate (foliar systemic) for leafminers in leaves Dinotefuran or Imidacloprid for soil treatments Spraying with systemic insecticides such as acephate are effective when larvae are present in the mines and malathion and carbaryl are effective for adults. Dinotefuran or imidacloprid will control leafminers when treating the soil. Please contact your local extension office for management recommendations. Information sources: 15) 32) Damage caused by boxwood leafminer to boxwood Photo credit: Bruce Watt, University of Maine, Bugwood.org, #

Boxwood Mite Eurytetranychus buxi
Overwinters as eggs on the underside of leaves More than eight generations per year The boxwood mite (Eurytetranychus buxi), also called boxwood spider mite, is in the family Tetranychidae. The boxwood mite is unusual as it feeds on both the upper and lower surfaces of leaves, while most spider mites only feed on the lower surface of leaves. Adults are green to yellowish brown in color and less than 0.5 mm long. The boxwood mite overwinters as eggs on the underside of leaves. They hatch in April and breed rapidly producing more than eight generation per year. Eggs are lemon-yellow in color, flattened on the bottom and slightly flattened on top. Larva is green in color and has 6 legs, while adults have 8 legs. All stages of boxwood mite damage boxwood leaves. Information sources: 3) 15) 32) Adult and egg of boxwood mite Photo credits: Rayanne Lehman, Pennsylvania Department of Agriculture, Bugwood.org: #UGA

Boxwood Mite Symptoms: Stippling Grayish, dingy and unhealthy leaves
Feeding damage on leaf surface Early symptoms are not noticeable because the mites are so tiny. The mites pierce the leaf and suck the plant sap, injecting toxic saliva causing stippling. This stipling looks like tiny, yellow scratches on the leaf surface early in the season. Although boxwood mites feed on young leaves, severe damage appears on second and third year leaves. These have a general grayish, dingy and unhealthy appearance. Information sources: 15) 32) Damage of boxwood mite Photo credits: Upper - Rayanne Lehman, Pennsylvania Department of Agriculture, Bugwood.org: #UGA , and lower - Eric R. Day, Virginia Polytechnic Institute and State University, Bugwood.org; #

Boxwood Mite Management:
Natural enemies include predatory mites and ladybird beetles Insecticides may kill the beneficial natural enemies Strong spray of water and horticultural oil s can get rid of adults and eggs Miticides such as tau-fluvalinate have also been used To control boxwood mite, natural enemies such as predator mites, ladybird beetles and other insects can be used as biological control to suppress mite populations. Application of insecticides may kill the beneficial insects and natural enemies of the mite so it is best to use these only when absolutely necessary. Mites can be knocked off the plant with a strong spray of water and horticultural oil can be applied to kill eggs and adult mites. Miticides such as tau-fluvalinate can be used for homeowners. Information sources: 15) 32) Damage caused by boxwood mite Photo credits: Eric R. Day, Virginia Polytechnic Institute and State University, Bugwood.org: #

Boxwood Psyllid Clear wings and strong legs for jumping
Feed on leaf surface and suck plant sap Overwinter as eggs Nymphs cause more damage Adult of boxwood psyllid The boxwood psyllid (Cacopsylla buxi) is in the family Psyllidae. Adult are small (3mm or 1/8 of an inch in length), greenish insects having clear wings and strong legs for jumping. They feed on the leaf surface and suck plant sap. The adult females lay their eggs on the outer scales of dormant buds. The eggs are stalked, measure 0.45mm long and 0.12mm across, and are milky white in color. They hatch before winter and the nymphs overwinter as first instar larvae. The nymphs are pale yellow to orange, somewhat flattened, and have red eyes. They are also covered in white waxy secretions. An interesting note here is that the first larval instars overwinter in the egg case from which they hatch. Adults appear again in the summer months. Nymphs feed on buds and expanding foliage. Adults also feed on boxwood but cause less damage than the nymphs. Only one generation occurs per year. Information sources: 2) 9) 15) 30) 32) Nymph of boxwood psyllid Photo credit: Adult - Wikimedia Commons, and nymph – Nancy Gregory, University of Delaware, Bugwood.org #

Boxwood Psyllid Symptoms Management Cupping of leaves and stunted twig
Acephate and Carbaryl for homeowner Dinotefuran or Imidacloprid for soil treatments The boxwood psyllid feeds on the leaf surface and sucks plant sap, causing a characteristic cupping of the leaves at the terminal and lateral buds of boxwood. Eventually, this feeding damage results in stunted twig growth. To control this insect pest, insecticides should be used when the damage is severe. Acephate and carbaryl can be used for homeowners. Dinotefuran or imidacloprid can be used for soil treatments. Dinotefuran should be applied for faster control because it may move into the shrubs more quickly than imidacloprid. Please contact your local extension office for management recommendations. Information sources: 9) 15) 32) Cupped and stunted leaves Photo credit: Left – Daniel Herms, Ohio State University, Bugwood.org #UGA

Questions? Contact: NPDN website First Detector Training Website:
Rachel McCarthy ) NPDN website First Detector Training Website:

Authors Kevin Ong, Ph.D. Associate Professor & Director of The Texas Plant Disease Diagnostic Laboratory, Texas A&M AgriLife Extension Service Raghuwinder Singh, D.P.M. Assistant Professor, Louisiana State University AgCenter Keumchul Shin, M.S. Doctor of Plant Medicine Program, University of Florida Molly Giesbrecht, M.S. Formerly of Texas Plant Disease Diagnostic Laboratory, Texas A&M AgriLife Extension Service

Editors Stephanie Stocks, M.S.
formerly of the Department of Entomology and Nematology, University of Florida Jennifer Carr, M.D.P. Lab manager, Biosecurity Research and Extension, Department of Entomology and Nematology, University of Florida Sage Thompson, Undergraduate assistant Biosecurity Research and Extension, Department of Entomology and Nematology, University of Florida

Reviewers Rachel McCarthy, MS
NPDN Training and Education Coordinator, Cornell University Amanda Hodges, Ph.D. Director of the Doctor of Plant Medicine Program, University of Florida

Publication Details This publication can be used for non-profit, educational use only purposes. Photographers retain copyright to photographs or other images contained in this publication as cited. This material was developed as a core training module for NPDN First Detector Training. Authors and the website should be properly cited. Images or photographs should also be properly cited and credited to the original source. Publication Date: June 2015

NPDN Partners United States Department of Agriculture Animal and Plant Health Inspection Service Plant Protection and Quarantine (USDA APHIS PPQ) Local and Regional Integrated Pest Management Programs Cooperative Agriculture Pest Survey Program (CAPS) National Plant board and State Departments of Agriculture Extension Disaster Education Network (EDEN) Center for Invasive Species and Ecosystem Health (Bugwood)

References 1) Boxwood (Buxus spp.)-Phytophthora Root and Crown Rot. Pacific Northwest Plant Disease Management Handbook. Accessed July 2) Boxwood Psyllid (Cacopsylla buxi). Plant disease and insect clinic factsheets. North Carolina State Cooperative extension. Accessed August 2014 3) Baker, James R. Boxwood Spider Mite. Insect and related pests of shrubs. North Carolina State University. Accessed August 2014 4) CABI Invasive Species Compendium. Calonectria pseudonaviculata. Accessed July 2014 5) Chalkley, D Systematic Mycology and Microbiology Laboratory, ARS, USDA. . Invasive Fungi. Shoot blight of boxwood-Calonectria pseudonaviculata. Accessed July 2014 mbuxicol

References 6) Clement, David. Volutella Blight of Boxwood. University of Maryland Extension. Accessed July 2014 7) Daughtrey, M New Blight Ravages Boxwood. Cornel University. Accessed July 8) Douglas, S Boxwood Blight: A new disease for Connecticut and the U.S. The Connecticut Agricultural Experiment Station. Accessed July _ pdf 9) Hamilton, C.C Insect Pests of Boxwood. New Jersey Agricultural Experiment Stations, Circular 178, pp 1-14. 10) Hebert, J.B., B. Gehesquiere, K. Heungens, and J.A. Crouch Phylogeography of the Boxwood Blight Fungus, Calonectria pseudonaviculata. Proceedings of the twenty-third annual Rutgers turfgrass symposium p36. Accessed July 2014

References 11) Henricot, B. and A. Culham Cylindrocladium buxicola, a new species affecting Buxus spp., and its phylogenetic status. Mycologia, 94(6): 12) Henricot, B., C. Gorton, G. Denton and J. Denton Studies on the Control of Cylindrocladium buxicola Using Fungicides and Host Resistance. Plant Disease 92: 13) Hemmelein, J. T. Dudek and J. Byrne. Boxwood blight disease identified in North America Claonectria pseudonaviculata or Cylindrocladium buxicola. Michican State University Extension. Accessed July 2014 14) Horst, R.K Westcott’s Plant Disease Handbook. 7th Edition. Springer Reference, New York. 15) IPM Series: Boxwood University of Maryland Extension HG 52. Accessed July 2014

References 16) Ivors, K. and A. Lebude A new pest to the U.S. Ornamental Industry: The “box blight” pathogen Cylindrocladium pseudonaviculatum = Cylindrocladium buxicola. North Carolina State University Pest Alert. Accessed July 2014 17) Ivors, K Prevention and Management of Boxwood Blight. North Carolina State University. Accessed July 2014 ment%20relations/Boxwood%20Blight/Box%20blight%20Guide% pdf 18) Luongo, L., M. Galli, A. Haegi, P. Proietti, and A. Belisario New Disease Reports Dec 2013, Volume 28: , 5. Accessed July 2014 19) Malpi-Wight, M., J.B. Hebert, R. Buckley, M.L. Daughtrey, N.F. Gregory, K. Rane, S. Tirpak, and J.A. Crouch First Report of Boxwood Blight Caused by Calonectria pseudonaviculata in Delaware, Maryland, New Jersey, and New York. Plant Disease 98(5): 698

References 20) National Agricultural Pest Information System (NAPIS). Purdue University. "Survey Status of Boxwood Blight; Leaf and Stem Blight - Calonectria pseudonaviculata (2011 to present)." Accessed July 2014 21) Phytophthora Root Rot on Woody Ornamentals. Alabama Cooperative Extension system ANR-571. Accessed July 2014 22) Rezaee, S., H. Kia-Daliri, K. Sharifi, Y. Ahangaran, and S. Hajmansoor Boxwood Blight Caused by Cylindrocladium buxicola in Tonekabon Forest. Applied Entomology and Phytopathology 80(2): 23) Singh, R., Graney, L., and Williamson, M First Report of Stem Canker of Boxwood caused by Colletotrichum theobromicola . Plant Dis. (in press). 24)USDA-APHIS-PPQ-CPHST and NCSU-Dept. of Plant Pathology. “The ‘box blight’ pathogen: Cylindrocladium pseudonaviculatum”. Accessed July v4.pdf

References 25) Vann, S. R. and Mason, D Boxwood Blight: A New Ornamental Disease Threat. University of Arkansas Division of Agriculture Research and Extension FSA Accessed July 2014 26) Vettraino, A.M., Franceschini, and S., Vannini, A., First Report of Buxus rotundifolia root and collar rot caused by Phytophthora citrophthora in Italy. Plant Disease 94, 272. 27) Vitale, A., P.W. Crous, L. Lombard, and G. Polizzi Calonectria diseases on ornamental plants in Europe and the Mediterranean basin: an overview. Journal of Plant Pathology, 95(3), 28) Weeda, S.M., and N.L. Dart Histological Evidence that Microsclerotia Play a Significant Role in Disease Cycle of the Boxwood Blight Pathogen in Southeastern United States and Implications for Disease Mitigation. Plant Health Progress. Online. Plant Health Progress doi: /PHP BR. 29) Weir, B.S., P.R. Jonson, and U. Damm “The Colletotrichum gloeosporioides species complex”. Studies in mycology, 73(1):

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