View source for Biology:Raspberry spur blight

{{Short description|Species of fungus}}
{{Speciesbox
|image = Didymella applanata (4).jpg
|image_alt = Didymella applanata on Rubus idaeus
|image_caption = ''Didymella applanata'' on ''[[Biology:Rubus idaeus|Rubus idaeus]]''
|genus = Didymella
|species = applanata
|authority = (Niessl) Sacc., (1882)
|synonyms = *''Ascochyta argillacea'' <small></small>
*''Didymosphaeria applanata'' <small></small>
*''Endophlaea applanata'' <small></small>
*''Mycosphaerella rubina'' <small></small>
*''Phoma argillacea'' <small></small>
*''Phyllosticta argillacea'' <small></small>
*''Sphaerella rubina'' <small></small>
*''Sphaeria applanata'' <small></small>
*''Xenodidymella applanata'' <small>(Niessl) Q. Chen & L. Cai, (2015)</small>
|synonyms_ref = <ref name="Chen2015">{{cite journal|author=Chen|display-authors=0|year=2015|title=Resolving the ''Phoma'' enigma|journal=Studies in Mycology|volume=82|pages=137–217|doi=10.1016/j.simyco.2015.10.003|pmid=26955202|pmc=4774273}}</ref>
}}
{{infobox plant disease
|name=Raspberry spur blight
|image=Didymella applanata (5).jpg
|caption=''Didymella applanata'' on ''[[Biology:Rubus idaeus|Rubus idaeus]]''
|common_names=
|hosts=[[Biology:Raspberry|Raspberry]]
|causal_agents=''Didymella applanata''
|vectors=
|EPPO_codes=DIDYAP
|distribution=
|treatment=
}}

'''Raspberry spur blight''' is caused by the fungus '''''Didymella applanata'''''.<ref>Ellis, Michael A. http://ohioline.osu.edu/hyg-fact/3000/pdf/HYG_3008_08.pdf "Spur Blight of Red Raspberries", 2008.</ref> This plant pathogen is more problematic on red raspberries ''([[Biology:Rubus idaeus|Rubus idaeus]])'' than on black or purple raspberries. The fungus infects the leaves first and then spreads to the cane. It causes necrotic spots on the cane near the base of the [[Biology:Petiole (botany)|petiole]] attachment.<ref name="http://www.mda.state.mn.us/plants/pestmanagement/ipm/~/media/Files/plants/ipm/20120907fruitipmart2.ashx">{{cite web|last=McCamant|first=Thaddeus|title=Apple, Raspberry, & Strawberry Pests|url=http://www.mda.state.mn.us/plants/pestmanagement/ipm/~/media/Files/plants/ipm/20120907fruitipmart2.ashx|publisher=Minnesota Department of Agriculture|accessdate=3 December 2012}}</ref>  Raspberry spur blight can cause a significant reduction in yield, fruit blight, premature leaf drop, and weak bud and cane growth. The magnitude of damage is not clearly understood in the United States, however, studies from Scotland suggest damage to the cane itself is limited.<ref name="ohioline">Ellis, Michael A. [http://ohioline.osu.edu/hyg-fact/3000/pdf/HYG_3008_08.pdf "Spur Blight of Red Raspberries"], 2008.</ref> The disease has minor economic impacts by reducing leaves in the summer or killing buds. Major economic damage occurs if the disease manages to kill the entire cane.<ref name="http://www.mda.state.mn.us/plants/pestmanagement/ipm/~/media/Files/plants/ipm/20120907fruitipmart2.ashx"/>
In the United States, this disease is found in Oregon and Washington.<ref name="Compendium of Raspberry and Blackberry Diseases and Insects.">{{cite web|title=Raspberry (Rubus sp.)-Spur Blight|url=http://pnwhandbooks.org/plantdisease/raspberry-rubus-sp-spur-blight|publisher=APS Press|accessdate=3 December 2012}}</ref>

==Signs==
In the late summer, the bark of infected areas split and the lesions produce fruiting bodies called [[Biology:Pycnidium|pycnidia]]. Pycnidia appear as small black dots to the naked eye and can be seen as flask-shaped structures under a microscope. Perithecia, another fruiting body, forms after the pycnidia. Perithecia appear as medium, black, erupting dots.<ref name="ohioline" /> In the spring, spur blight can be mistaken for winter injury therefore it is important to scout for these signs in September to assess the potential damage that will be done in the following season.<ref name="http://www.mda.state.mn.us/plants/pestmanagement/ipm/~/media/Files/plants/ipm/20120907fruitipmart2.ashx"/>

==Symptoms==
Infection generally occurs in the late spring when the environment is wet and optimal for fungus to proliferate. Symptoms do not become visible until mid to late summer. Visible symptoms include purple and brown expansive lesions appearing below buds, leaves and the lower portion of the stem. [[Biology:Leaflet (botany)|leaflets]] that are infected have wedge-shaped brown patches. Infected leaflets may fall, leaving only the petiole and canes behind. During the next season, branch growth from diseased canes will often be weak and wilted.<ref name="fruit.cornell">Heidenreich, Cathy. http://www.fruit.cornell.edu/berry/ipm/ipmpdfs/Raspberry%20cane%20disease%20mgmt.pdf "Managing Raspberry Cane Diseases", March 13, 2006.</ref>

==Disease cycle==
The raspberry spur blight fungus spreads through the [[Biology:Pycniospore|pycniospore]]s that are released from the pycnidia. The spores are released and infect other raspberry plants with the help of rain through open wounds or natural openings.<ref>"IPM : Fruits : Spur Blight and Cane Blight of Raspberries." Integrated Pest Management at the University of Illinois. N.p., n.d. Web. 23 Oct. 2012. {{cite web |url=http://ipm.illinois.edu/fruits/diseases/spur_blight/index.html |title=IPM : Fruits : Spur Blight and Cane Blight of Raspberries |accessdate=2012-10-24 |url-status=dead |archiveurl=https://web.archive.org/web/20130215222801/http://ipm.illinois.edu/fruits/diseases/spur_blight/index.html |archivedate=2013-02-15 }}.</ref> The fungus will then spread throughout the plant and will live in lesions during the winter to survive. After winter there are two spore types that are formed pycniospores and [[Biology:Ascospore|ascospore]]s. The pycniospores come from [[Biology:Conidium|conidia]] and the ascospores come from the perithecia that was formed. Both of these spores will spread through rainfall onto new plants and start the process over again.<ref>Ellis, Mike A., and Mizuho Nita. "Organic Fruit Management Workshop." Ohio Agricultural Research and Development Center - Home. N.p., n.d. Web. 23 Oct. 2012. http://www.oardc.ohio-state.edu/fruitpathology/organic/brambles/All-Brambles.html.</ref>

==Environment==
The environments that are favorable for raspberry spur blight are conditions that usually favor spore production. Infection generally occurs in late spring when the environment is wet and moist. Thick and dense patches of raspberries also increase infection.

==Disease control==
Methods of controlling this disease include improving air circulation to allow fast drying of the plant, removing weeds that slow airflow, reducing the number of wet periods the plant is exposed to, avoiding the use of fertilizers because it promotes growth of susceptible tissue targeted by the pathogen, thinning plants for better light exposure and removing possible sources of inoculum. Removing sources of inoculum can be completed by destroying wild brambles that may carry the disease, removing and destroying all previously infected material and using special fungicide in certain situations.<ref name="ohioline" />

Other methods include starting with disease free plants, buying cultivars that are less susceptible to raspberry spur blight such as Brandywine, Killarney, Latham and Newburgh, and avoiding cultivars that have greater susceptibility such as Royalty, Titan, Canby, Skeena, Willamette, Reveille, and Sentry. Willamette readily infects with spur blight but is tolerant to the disease and still produces satisfactory yields.<ref name="fruit.cornell"/>

It is important to minimize plant wounding and maintain proper soil nutrition. If you plan on pruning, always allow four to five days for healing before exposing the plants to water. Chemicals can be used in some cases. However, the spraying of chemicals is only efficient if it is sprayed on the entire raspberry plant.<ref>Rekanović, E., Stepanović, M., Potočnik, I., Milijašević-Marčić, S., Todorović, B., Duduk, B. and Gavrilović, V. 2012. FIELD EFFICACY OF FUNGICIDES AND BIOFUNGICIDES IN THE CONTROL OF SPUR BLIGHT OF RASPBERRIES IN SERBIA. Acta Hort. (ISHS) 946:289-292
http://www.actahort.org/books/946/946_47.htm</ref>  These include [[Chemistry:Lime sulfur|lime sulfur]] or [[Chemistry:Copper|copper]] application, [[Chemistry:Captan|captan]]/fenhexamid mixture (Captevate 68WDG) applied when 8-10" shoot growth, and [[Biology:Strobilurin|Strobilurin]]s.<ref name="fruit.cornell" /> Recent research indicates that [[Biology:Chitinase|chitinase]]s may effectively control against raspberry spur blight. Specifically, chitinases, when applied, were found to reduce lesion size, and control infection of internal tissues.<ref>Shternshis, Margarita et al. (2006). "The effect of chitinase on ''Didymella applanata'', the causal agent of raspberry cane spur blight," Biocontrol, Volume 51, Number 3 (2006), 311-322, DOI: 10.1007/s10526-005-1034-2</ref>
Notably, the application of Phytoverm, a ''Streptomyces avermitilis'' metabolite, had a similar inhibitory effect on disease growth.<ref>Shternshis, Margarita et al. (2002). "Field testing of BACTICIDE (R), PHYTOVERM (R) and CHITINASE for control of the raspberry midge blight in Siberia," Biocontrol, Volume 47, Issue 6, 697-706, DOI: 10.1023/A:1020574914831</ref> Other plant pathogens have also been found to reduce the growth rate of casual agent ''D. applanata'' such as entornopathogenic fungi ([[Biology:Hyphomycetes|Hyphomycetes]]).<ref>Shternshis, Margarita et al. (2005). "The influence of enthomopathogenic fungi and formulation phytoverm on the raspberry cane midge (Resseliella theobaldi) and spur blight causal agent (''Didymella applanata'')," MIKOLOGIYA I FITOPATOLOGIYA, Volume 39, Issue 1, 76-82, WOS:000228409300012</ref>

==Importance==
The United States is the third largest country in producing raspberries. Raspberries are grown all over the country, but the majority are produced in Washington, California and Oregon.<ref>{{cite web|url=http://www.agmrc.org/commodities__products/fruits/raspberries/|title=Raspberries - Agricultural Marketing Resource Center|date=|website=www.agmrc.org|accessdate=16 February 2018}}</ref> However, in the United States the magnitude of damage caused by raspberry spur blight is not clearly understood.<ref name="ohioline"/>

==References==
{{Reflist}}

{{Taxonbar|from=Q5274261|from2=Q7295200}}

[[Category:Pleosporales]]

{{Sourceattribution|Raspberry spur blight}}