Pathogens
Botryosphaeria canker is an important disease for numerous trees and shrubs across forests, plantations, orchards, and managed landscapes. To date, there are more than 20 closely related genera in the family Botryosphaeriaceae, many of which were previously described only as Botryosphaeria (Zhang et al. 2021a, 2021b; Rathnayaka et al. 2023). Some of these genera are well known to green industry professionals, such as Botryosphaeria sensu stricto (s.s.), Diplodia, and Sphaeropsis (Sinclair and Lyon 2005). However, much remains to be understood about the taxonomy and host range of many lesser-known species. Therefore, for the purpose of this fact sheet, these fungi will be collectively referred to as Botryosphaeria sensu lato (s.l.).
Currently recognized species in the Botryosphaeriaceae family include Alanomyces, Barriopsis, Botryobambusa, Botryosphaeria s.s. (type genus), Cophinforma, Dibotryon, Diplodia, Dothiorella, Endomelanconiopsis, Eutiarosporella, Lasiodiplodia, Macrophomina, Mucoharknessia, Neodeightonia, Neofusicoccum, Neoscytalidium, Oblongocollomyces, Phaeobotryon, Sakireeta, Sardiniella, Sphaeropsis, and Spencermartinsia (Zhang et al. 2021a; Rathnayaka et al. 2023).
Hosts
Due to the tremendous diversity of genera and species in Botryosphaeria s.l., hundreds of woody plants are susceptible to infection, especially when they are stressed (Sinclair and Lyon 2005). Many Botryosphaeria s.l. species are relatively host-specific, while a few, such as Botryosphaeria dothidea, have broad host ranges among conifers and hardwoods (Batista et al. 2021; Silva-Valderrama et al. 2024).
Based on samples submitted to the UMass Plant Diagnostic Laboratory, some of the most frequently diseased trees and shrubs in managed landscapes of southern New England include maple (Acer), dogwood (Cornus), ash (Fraxinus), honeylocust (Gleditsia tricanthos), holly & inkberry (Ilex), magnolia (Magnolia), apple & crabapple (Malus), spruce (Picea), pine (Pinus), cherry (Prunus), oak (Quercus), rhododendron (Rhododendron), hemlock (Tsuga), and elm (Ulmus).
Symptoms & Signs
Cankering fungi like Botryosphaeria s.l. attack the phloem, cambium, and outer sapwood of woody plants (Sinclair and Lyon 2005). The subsequent damage disrupts or ceases transport of water and minerals beyond the infection site. They invade the host through various wounds and natural openings, and plants weakened by biotic and abiotic stresses are particularly susceptible to disease. The extent of Botryosphaeria canker infections can range from small areas of necrotic bark, girdled shoots and small branches, and extensive cambial death of large branches and even the main trunk. Symptoms of the disease are variable depending on the host, pathogen, and predisposing stresses present (Sinclair and Lyon 2005).
Typical symptoms of infection include thinning canopies, browning and prematurely shedding foliage, scattered branch dieback, and eruptive cankers on the bark. There may also be sunken lesions on shoots and branches with sap-stained bark, along with cracking, splitting, and sloughing bark or oozing sap near the canker site (Sinclair and Lyon 2005). Conversely, there may be no visible symptoms of infection aside from a progressively worsening canopy dieback. Shaving the bark on branches suspected of harboring Botryosphaeria s.l. may reveal discolored and stained vascular tissue in some cases. By themselves, the individual cankers often cause only minimal damage, but they are produced in such large numbers that they coalesce to girdle shoots and branches. It's less common to find the pathogen on large, primary branches but exceptions do occur. At times, even the main trunk can be infected (Munck et al. 2016).
During wet and mild weather, primarily during the spring, black pads of fungal tissue (pycnidia or pseduothecia) swell from the site of the canker and erupt to release large volumes of spores (conidia) (Sinclair and Lyon 2005). These may be visible on infected shoots and branches with a hand lens. The spores are blown and splashed onto adjacent stems and branches to initiate new infection centers. Spores will germinate and invade any wounds, or natural openings present in the bark. Insects are also vectors of the pathogen or create infection sites through feeding (Michailides et al. 2016; Panzavolta et al. 2017). The fungus overwinters within infected and dead branches in the canopy or those that have fallen to the ground. Predisposing stresses include, but are not limited to, winter injury, transplant shock, drought, insect feeding, root disease, excessive pruning, and mechanical injury (i.e. root compaction and severing).
Management
Generally, Botryosphaeria s.l. species behave as opportunistic pathogens that attack weakened and stressed hosts (Sinclair and Lyon 2005). In addition, certain Botryosphaeria s.l. species can survive as endophytes, invading hosts yet causing no observable symptoms until the plants become stressed (Marsberg et al. 2017; Blumenstein et al. 2021). As with any opportunistic pathogen, minimizing stresses that predispose woody plants to infection is critical. Maintaining high plant vigor is important since natural defenses are often sufficient to minimize damage by the pathogen. To that end, irrigate susceptible trees and shrubs on regular intervals during extended dry periods to minimize drought stress, fertilize if soil nutrients are lacking, ensure the root zone is mulched to help retain soil moisture, limit mechanical wounds (e.g. string trimmers), avoid excessive pruning, especially on recently transplanted trees and shrubs, and avoid needless damage to the canopy and roots. For certain trees and shrubs, especially those with thin and easily wounded bark (e.g. beech, Japanese maple, dogwood), regular sanitation pruning should take place to remove dead twigs from the canopy. If possible, avoid pruning during wet periods in the spring as this is the time when the fungus is most actively sporulating, and sanitize pruning tools after working with plants known or suspected of being infected by Botryosphaeria canker.
Pruning of cankered stems and branches, at least 6–12 inches away from the blighted tissue (if possible), and removal of the diseased material from the site is the best management practice. Repeated scouting and pruning are often required, and complete eradication is difficult to achieve (Moorman and Lease 1999). For large and mature trees and shrubs, fungicides may also be helpful in suppressing the pathogen once the disease has been identified. Keep in mind that it can be difficult to control cankering fungi like Botryosphaeria s.l. with fungicides because the fungus lives beneath the bark and may be present on branches that show no symptoms of disease. Fungicides registered for use against Botryosphaeria s.l. include: azoxystrobin, boscalid, copper salts of fatty and rosin acids, copper hydroxide, mancozeb, phosphites, propiconazole, pyraclostrobin, tebuconazole, thiophanate-methyl, and trifloxystrobin. Applications should be made in the spring to protect newly developing tissues from becoming infected before these tissues mature.
A greenhouse trial of Botryosphaeria canker management on potted redbuds (Cercis canadensis) found that canker lesion length was best controlled using two biofungicides applied directly to the wounds (BotryStop and RootShield PLUS), and a combination fungicide (triticonazole + pyraclostrobin) applied as a foliar treatment (Subedi and Baysal-Gurel 2025). Chemical control may not be required if the cankered stems and branches can be thoroughly pruned and removed from the site. For large trees, a lower trunk drench or injection with phosphites may be the most practical option where fungicide drift is a concern. Do not apply fungicides to trees and shrubs that are actively flowering as the chemicals are harmful to pollinators.
References
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Blumenstein K, Bußkamp J, Langer GJ, Langer EJ, and Terhonen E. 2021. The Diplodia tip blight pathogen Sphaeropsis sapinea is the most common fungus in Scots Pines’ mycobiome, irrespective of health status—A case study from Germany. Journal of Fungi 7: 607. https://doi.org/10.3390/jof7080607
Marsberg A, Kemler M, Jami F, Nagel JH, Postma‐Smidt A, Naidoo S, Wingfield MJ, Crous PW, Spatafora JW, Hesse CN, and Robbertse B. 2017. Botryosphaeria dothidea: a latent pathogen of global importance to woody plant health. Molecular Plant Pathology 18(4): 477–488. https://doi.org/10.1111/mpp.12495
Michailides TJ and Morgan DP. 2016. Association of Botryosphaeria panicle and shoot blight of pistachio with injuries of fruit caused by Hemiptera insects and birds. Plant Disease 100(7): 1405–1413. https://doi.org/10.1094/PDIS-09-15-1077-RE
Moorman GW and Lease RJ. 1999. Effects of pruning in the management of dogwood and pine branch dieback in the landscape. Journal of Arboriculture 25(5): 274-277. https://doi.org/10.48044/jauf.1999.037
Munck IA, Wyka SA, Bohne MJ, Green WJ, and Siegert NW. 2017. First report of Diplodia corticola causing bleeding cankers on black oak (Quercus velutina). Plant Disease 101: 257. https://doi.org/10.1094/PDIS-08-16-1118-PDN
Panzavolta T, Panichi A, Bracalini M, Croci F, Ginetti B, Ragazzi A, Tiberi R, and Moricca S. 2017. Dispersal and propagule pressure of Botryosphaeriaceae species in a declining oak stand is affected by insect vectors. Forests 8(7): 228. https://doi.org/10.3390/f8070228
Rathnayaka AR, Chethana KT, Phillips AJ, Liu JK, Samarakoon MC, Jones EG, Karunarathna SC, and Zhao CL. 2023. Re-evaluating Botryosphaeriales: Ancestral state reconstructions of selected characters and evolution of nutritional modes. Journal of Fungi 9(2): 184. https://doi.org/10.3390/jof9020184
Silva-Valderrama I, Úrbez-Torres JR, and Davies TJ. 2024. From host to host: The taxonomic and geographic expansion of Botryosphaeriaceae. Fungal Biology Reviews 48: 100352. https://doi.org/10.1016/j.fbr.2023.100352
Sinclair WA and Lyon HH. 2005. Diseases of Trees and Shrubs, 2nd edn. Cornell University Press, Ithaca, NY.
Subedi P and Baysal-Gurel F. 2025. Evaluation of fungicides, biofungicides, and plant-based extract for the management of stem canker Caused by Botryosphaeria dothidea in eastern redbud (Cercis canadensis). HortScience 60(11): 1994–2001. https://doi.org/10.21273/HORTSCI18841-25
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Zhang Y, Zhou Y, Sun W, Zhao L, Pavlic-Zupanc D, Crous PW, Slippers B, and Dai Y. 2021b. Toward a natural classification of Botryosphaeriaceae: a study of the type specimens of Botryosphaeria sensu lato. Frontiers in Microbiology 12: 737541. https://doi.org/10.3389/fmicb.2021.737541