Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Datasheet

Diaporthe helianthi
(stem canker of sunflower)

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Datasheet

Diaporthe helianthi (stem canker of sunflower)

Summary

  • Last modified
  • 26 November 2019
  • Datasheet Type(s)
  • Documented Species
  • Pest
  • Preferred Scientific Name
  • Diaporthe helianthi
  • Preferred Common Name
  • stem canker of sunflower
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Fungi
  •     Phylum: Ascomycota
  •       Subphylum: Pezizomycotina
  •         Class: Sordariomycetes
  • Summary of Invasiveness
  • No effect of D. helianthi on wild Helianthus spp. in North America has been documented. Though the fungus could be said to have invaded Europe, its spread has probably been mediated by human activity r...

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    Compendia
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    OX10 8DE
    UK
    compend@cabi.org
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Identity

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Preferred Scientific Name

  • Diaporthe helianthi Munt.-Cvetk., Mihaljc. & M. Petrov

Preferred Common Name

  • stem canker of sunflower

Other Scientific Names

  • Phomopsis helianthi Munt.-Cvetk., Mihaljc. & M. Petrov

International Common Names

  • English: grey stem spot of sunflower; Phomopsis stalk rot of sunflower; Phomopsis stem canker of sunflower; stalk rot: sunflower
  • French: Phomopsis du tournesol
  • Russian: Fomopsis podsolnechnika

EPPO code

  • DIAPHE (Diaporthe helianthi)

Summary of Invasiveness

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No effect of D. helianthi on wild Helianthus spp. in North America has been documented. Though the fungus could be said to have invaded Europe, its spread has probably been mediated by human activity rather than by natural means. In any case, sunflower is an annual exotic crop in Europe, planted in monoculture, and the disease has not affected the extent of sunflower cultivation. So D. helianthi cannot be said to be invasive.

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Fungi
  •         Phylum: Ascomycota
  •             Subphylum: Pezizomycotina
  •                 Class: Sordariomycetes
  •                     Subclass: Sordariomycetidae
  •                         Order: Diaporthales
  •                             Family: Diaporthaceae
  •                                 Genus: Diaporthe
  •                                     Species: Diaporthe helianthi

Notes on Taxonomy and Nomenclature

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Diaporthe helianthi was described as the causal pathogen of Phomopsis stem canker, when the disease was first described from Voivodina region of the former Yugoslavia in 1980 (Muntanola-Cvetkovic et al., 1981).

Description

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The ascoma (perithecia) of D. helianthi form on overwintered crop debris, are 290-450 µm diameter with a prominent beak, 350-600 µm long. Asci are colourless, 8-spored, sac-like, 44-76.5 x 7.5-12.5 µm. Ascospores are colourless, two-celled, elliptical, and constricted at the septum, 12.5-19 x 2.8-12.5 µm. Conidioma (pycnidia) are brown to black, spherical, ostiolate, submersed in host tissue, 120-450 µm diameter (Muntanola-Cvetkovic et al., 1981). They contain two types of conidia: alpha-conidia, which are biguttulate, fusiform, and easily germinate on artificial media, 8-21 x 1.7-5.5 µm; and beta-conidia, which are unicellular, filiform, rarely germinate, 16-42 x 0.5-6.9 µm. The proportions of alpha- and beta-conidia vary among isolates, and with production under natural or artificial culture conditions.

Distribution

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After initial concern in Europe about the appearance of this new sunflower disease, control methods have been developed in the main sunflower-growing countries and the 'profile' of the disease has fallen. It is likely that it now occurs in most European countries where sunflowers are grown.

A record of D. helianthi in California published in previous versions of the Compendium was erroneous. The paper cited for this record, Gulya et al. (2012), states that this disease is not present in California.

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Asia

PakistanPresentCABI/EPPO, 1999; EPPO, 2014

Africa

MoroccoPresentCABI/EPPO, 1999; EPPO, 2014

North America

MexicoPresentCABI/EPPO, 1999; EPPO, 2014
USARestricted distributionCABI/EPPO, 1999; EPPO, 2014; Mathew et al., 2015
-IllinoisPresentMeyer et al., 2009
-MinnesotaPresentHajdu et al., 1984; CABI/EPPO, 1999; EPPO, 2014; Mathew et al., 2015
-North DakotaPresentHajdu et al., 1984; Gulya et al., 2012; Mathew et al., 2015
-OhioPresentHerr et al., 1983; CABI/EPPO, 1999; EPPO, 2014
-South DakotaPresentMathew et al., 2015
-TexasPresentYang and Gulya, 1984; CABI/EPPO, 1999; EPPO, 2014

South America

ArgentinaPresentCABI/EPPO, 1999; EPPO, 2014; Mancebo et al., 2019
VenezuelaPresentCABI/EPPO, 1999; EPPO, 2014

Europe

BulgariaPresentBistrichanov et al., 2000; Entcheva, 2002
CroatiaPresentJurkovic and Culek, 1998
FranceWidespreadLamarque and Perny, 1985; Regnault, 1985; CABI/EPPO, 1999; EPPO, 2014
HungaryPresentNemeth et al., 1981; CABI/EPPO, 1999; EPPO, 2014
ItalyRestricted distributionCABI/EPPO, 1999; EPPO, 2014
MoldovaPresentBogdanova et al., 1986; CABI/EPPO, 1999; EPPO, 2014
RomaniaPresentCABI/EPPO, 1999; EPPO, 2014
Russian FederationRestricted distributionCABI/EPPO, 1999; EPPO, 2014
-Central RussiaRestricted distributionCABI/EPPO, 1999; EPPO, 2014
-Southern RussiaRestricted distributionCABI/EPPO, 1999; EPPO, 2014
SerbiaPresentCABI/EPPO, 1999; EPPO, 2014
SlovakiaPresentCABI/EPPO, 1999; EPPO, 2014
SpainPresentCABI/EPPO, 1999; EPPO, 2014
UkrainePresentCABI/EPPO, 1999; EPPO, 2014
Yugoslavia (Serbia and Montenegro)Present1980Muntanola-Cvetkovic et al., 1981; CABI/EPPO, 1999

History of Introduction and Spread

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After Phomopsis stem canker was first reported in former Yugoslavia in Europe, it was soon reported in several sunflower-producing countries including Hungary (Nemeth et al., 1981), Bulgaria (Mihailova 1984), USA (Herr et al., 1983; Yang et al., 1984; Hajdu et al., 1984; Mathew et al., 2015), France (Lamarque and Perny, 1985; Regnault, 1985), Ukraine and Moldova (Bogdanova et al., 1986), and Russia (Scripka et al., 1993). In all of these countries, D. helianthi was assumed to be the only fungus causing Phomopsis stem canker. However, several researchers suspected that Phomopsis stem canker was caused by other species of Diaporthe, besides D. helianthi (Aćimović and Štraser, 1982; Herr et al., 1983; Yang and Gulya, 1984).

Risk of Introduction

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D. helianthi presents a considerable security risk to sunflower cultivation in Australia (National Plant Biosecurity report 2014), China (USDA-FAS, 2007), Iran (Bureau of Plant Pest Surveillance and Pest Risk Analysis, 2015) and Russia (Savotikov and Smetnik, 1995).

Hosts/Species Affected

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D. helianthi can infect members of the Asteraceae family, which includes wild sunflower (Helianthus annuus), Italian cocklebur (Xanthium italicum), common cocklebur (Xanthium strumarium), Noogoora burr (Xanthium pungens) and burdock (Arctium lappa) (Vrandecic et al., 2010). Other hosts of D. helianthi such as annual marsh elder (Iva annua var. annua) and ragweed (Ambrosia psilostachya) have been identified in the USA using molecular techniques (Gilley et al., 2019); however, the pathogenicity has not been tested.

Growth Stages

Top of page Flowering stage, Fruiting stage, Vegetative growing stage

Symptoms

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D. helianthi infects sunflower during the reproductive growth stages and early symptoms include brown, irregularly-shaped spots at the tip of the leaves which extend into large patches from the leaf margin. The leaf surrounding the veins may be yellow (chlorotic), later becoming brown (necrotic), and eventually the entire leaf dies. The infection spreads from the dead leaf through the petiole, which turns dark brown to reach the stem where a light-to-dark brown lesion develops at the node. Over time, the lesions at the node increase in length and may girdle the stem, when the weather conditions are conducive for disease development. The fungus can also degrade the pith tissue beneath the epidermis and cause the stem to become hollow and lodge. 

List of Symptoms/Signs

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SignLife StagesType
Fruit / lesions: black or brown
Fruit / reduced size
Inflorescence / dwarfing; stunting
Inflorescence / lesions; flecking; streaks (not Poaceae)
Leaves / necrotic areas
Seeds / empty grains
Seeds / lesions on seeds
Stems / discoloration
Stems / lodging; broken stems
Stems / necrosis
Whole plant / plant dead; dieback
Whole plant / uprooted or toppled

Biology and Ecology

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Development of Phomopsis stem canker on sunflower plants begins with the release of ascospores that are produced in the perithecia maturing on the crop residues. These spores are splashed by rain or blown by wind onto the sunflower plants. The ascospores infect the older leaves along the margin via guttation droplets and the infection requires temperatures anywhere between 20 and 25°C (Pinochet, 1995) and rainfall. After the leaf infection, the fungal mycelia progress down the petiole to infect the stem systemically where an elongated light to dark-brown lesion is formed (Muntañola-Cvetkovic et al., 1991). The hyphae enters through the vascular system and spreads via the cortex (Muntañola-Cvetkovic et al., 1989) where formation of pycnidia is initiated.

Means of Movement and Dispersal

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The ascospores can travel considerable distance from infected hosts (such as weed hosts or diseased sunflower) and overwintering structures in crop debris. These spores infect sunflower mainly because of no air movement and relative humidity that develops from the canopy (Mihaljcevic et al., 1985). 

Seedborne Aspects

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Seeds in heavily infected capitula can become infected, but it is unlikely that such seeds would either be viable or be harvested and traded. Slyusar' et al. (1998) showed that the fungus in infected seeds loses viability after storage for 10 months. Battilani et al. (2003) consider that seed transmission has low importance as a source of inoculum in areas that are already infested, but could be significant as a means of introduction to new areas. Smetnik et al. (1998) are concerned about seed transmission as a means of spread of the disease in Russia

Plant Trade

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Plant parts liable to carry the pest in trade/transportPest stagesBorne internallyBorne externallyVisibility of pest or symptoms
Flowers/Inflorescences/Cones/Calyx fruiting bodies; hyphae Yes Pest or symptoms not visible to the naked eye but usually visible under light microscope
Fruits (inc. pods) fruiting bodies; hyphae Yes Pest or symptoms not visible to the naked eye but usually visible under light microscope
Leaves fruiting bodies; hyphae Yes Pest or symptoms not visible to the naked eye but usually visible under light microscope
Stems (above ground)/Shoots/Trunks/Branches fruiting bodies; hyphae Yes Pest or symptoms not visible to the naked eye but usually visible under light microscope
True seeds (inc. grain) fruiting bodies; hyphae Yes Pest or symptoms not visible to the naked eye but usually visible under light microscope
Plant parts not known to carry the pest in trade/transport
Bark
Bulbs/Tubers/Corms/Rhizomes
Growing medium accompanying plants
Roots
Seedlings/Micropropagated plants
Wood

Wood Packaging

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Wood Packaging not known to carry the pest in trade/transport
Loose wood packing material
Non-wood
Processed or treated wood
Solid wood packing material with bark
Solid wood packing material without bark

Impact

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Phomopsis stem canker caused by D. helianthi and other species of Diaporthe is one of the major diseases of sunflower. The disease can compromise yield by 30-40% in the USA and Europe (Harveson et al., 2016; Mathew et al. 2018a).

Impact: Environmental

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D. helianthi has only been recorded to attack sunflower, and this plant is an exotic annual crop, grown as a monoculture, in Europe. Possibilities for any effect on the environment are therefore limited. Fungicides are in any case used on sunflower against other pathogens, so any impact through pesticide load on the environment is difficult to evaluate. The impact of the disease has not been such as to reduce its cultivation, and thus affect land use.

Impact: Biodiversity

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In the absence of any knowledge of where D. helianthi is native, or of any records of it attacking wild plants, it is impossible to assess any effect on biodiversity. As sunflower is native to North America, such effects could exist there, but their significance would depend on whether the fungus is or is not native to North America, and whether it does have other hosts. The subject is not apparently under study in North America.

Prevention and Control

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Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

D. helianthi can survive in crop residues for up to 5 years (Masirevic and Gulya, 1992) and thus, tillage or burying the crop residues is recommended. Crop rotation with non-hosts (small grains and maize) is recommended to reduce the inoculum levels of the pathogen. Weeds can host D. helianthi and other species of Diaporthe (Thompson et al., 2015) and it is important to manage weeds in a sunflower field. Fungicides have been used in the USA and Europe to manage Phomopsis stem canker. For example, in Europe, Debaeke et al. (2003) observed that application of a protectant fungicide at the R1 growth stage can reduce the incidence of Phomopsis stem canker. In the USA, Olson (2017) observed greater yield in plots with one application of pyraclostrobin at the R1 growth stage on susceptible and partially tolerant hybrids when comparing with plots where fungicides were not sprayed. As for genetic resistance, studies have suggested that resistance to D. helianthi is quantitative in nature (Viguié et al., 1999). Gulya (1997) evaluated 1106 accessions of the USDA cultivated sunflower collection and 2% of the total accessions had resistance to the disease. Talukder et al. (2014) identified 30 parental lines from Russia and Europe, which have resistance to D. helianthi in the field. More recently, Mathew et al. (2018b) screened 54 USDA cultivated sunflower accessions for resistance to D. helianthi in the greenhouse and identified 13 accessions that were resistant to D. helianthi.

References

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Acimovic M, Straser N, 1982. Phomopsis sp. - a new parasite of sunflower. Zastita Bilja, 33(2):117-158

Battilani P, Rossi V, Girometta B, Delos M, Rouzet J, André N, Esposito S, 2003. Estimating the potential development of Diaporthe helianthi epidemics in Italy. Bulletin OEPP/EPPO Bulletin, 33: (in press)

Bistrichanov S, Alexandrov V, Hristov I, 2000. Impact of some agrotechnical factors on the diseases' spreading on sunflower in the North Western Bulgaria. Pochvoznanie, Agrokhimiya i Ekologiya, 35(5):37-40; 5 ref

Bogdanova, V. N., Karadzova, L.V., Steinberg, M.E., 1986. (Vovremia obnaruzit Phomopsis). Seljskoe hozjaistvo Moldavii, 12, 24-25.

CABI/EPPO, 1999. Diaporthe helianthi. In: Distribution Maps of Plant Diseases, April (Edition 1). (No. 776) . Wallingford, UK: CAB International.

Debaeke, P., Estragnat, A., Reau, R., 2003. Influence of crop management on sunflower stem canker (Diaporthe helianthi). Agronomie, 23(7), 581-592. doi: 10.1051/agro:2003032

Delos M, Moinard J, 1997. Phomopsis on sunflower. Recent progress in disease forecasting. Phytoma, 49(492):17-21; 19 ref

Dozet B, Atlagic J, Vasic D, 1996. Transferring stem canker resistance from Helianthus tuberosus L. into inbred line of sunflower by embryo rescue technique. Helia, 19(25):87-94; 20 ref

Entcheva V, 2002. Variation in the aggressiveness of isolates from Phomopsis/Diaporthe helianthi Munt.-Cvet. et al. on sunflower. Bulgarian Journal of Agricultural Science, 8(4):349-352

EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm

Gilley, M., Kontz, B., Mathew, F., Markell, S., 2019. Identification of crop and weed species as possible hosts to the pathogens causing Phomopsis stem canker on sunflower. In: Proceedings of the 41st Annual Sunflower Research Forum, Fargo, ND, January 9-10, 2019

Gulya TJ, Rooney-Latham S, Miller JS, Kosta K, Murphy-Vierra C, Larson C, Vaccaro W, Kandel H, Nowatzki JF, 2012. Sunflower diseases remain rare in California seed production fields compared to North Dakota. Plant Health Progress, No.December:PHP-2012-1214-01-RS. http://www.plantmanagementnetwork.org/php/elements/sum2.aspx?id=10506

Gulya, T. J., 1997. Phomopsis stem canker resistance in USDA and commercial sunflower germplasm. In: Proceedings of the 19th Sunflower Research Workshop, Fargo, ND, USA . 76-78.

Hajdu, F., Baumer, J. S., Gulya, T., 1984. Occurrence of Phomopsis stem canker in Minnesota and North Dakota. In: Proceedings of the Sunflower Research Workshop, Bismarck, North Dakota, USA . 15.

Harveson, R. M., Markell, S. G., Block, C. C., Gulya, T. J., 2016. Compendium of sunflower diseases and pests, [ed. by Harveson, R. M., Markell, S. G., Block, C. C., Gulya, T. J.]. St. Paul, USA: American Phytopathological Society (APS Press).140 pp.

Herr LJ, Lipps PE, Watters BL, 1983. Diaporthe stem canker of sunflower. Plant Disease, 67(8):911-913

Jurkovic D, Culek M, 1998. Incidence of the most important sunflower diseases in eastern Croatia. Fragmenta Phytomedica et Herbologica, 26(1/2):67-75; 5 ref

Lamarque, C., Perny, R. A., 1985. (Nouvelle maladie du tournesol: Le phomopsis). Cultivar, 179, 57-59.

Mancebo, M. F., Bazzalo, M. E., Reid, R. J., Kontz, B., Mathew, F. M., 2019. First report of Diaporthe gulyae causing Phomopsis stem canker of sunflower (Helianthus annuus L.) in Argentina. Plant Disease, 103, 1769.

Masirevic, S., Gulya, T. J., 1992. Sclerotinia and Phomopsis - two devastating sunflower pathogens. Field Crop Res, 30, 271-300.

Mathew, F. M., Alananbeh, K. M., Jordahl, J. G., Meyer, S. M., Castlebury, L. A., Gulya, T. J., Markell, S. G., 2015. Phomopsis stem canker: a reemerging threat to sunflower (Helianthus annuus) in the United States. Phytopathology, 105(7), 990-997.

Mathew, F., Harveson, R., Gulya, T., Thompson, S., Block, C., Markell, S., 2018. Phomopsis stem canker of sunflower. Plant Health Instructor, doi: 10.1094/PHI-I-2018-1103-01

Mathew, F., Olson, T., Marek, L., Gulya, T., Markell, S., 2018. Identification of sunflower (Helianthus annuus) accessions resistant to Diaporthe helianthi and Diaporthe gulyae. Plant Health Prog, 19, 97-102.

Meyer MD, Zhang GR, Pedersen DK, Bradley CA, 2009. First report of phomopsis stem canker of sunflower in Illinois caused by Phomopsis helianthi. Plant Disease, 93(7):760. http://apsjournals.apsnet.org/loi/pdis

Mihaljcevic M, Muntanola-Cvetkovic M, Vukojevic J, Petrov M, 1985. Source of infection of sunflower plants by Diaporthe helianthi in Yugoslavia. Phytopathologische Zeitschrift, 113(4):334-342

Mihaljcevic M, Vukojevic J, 1994. Diaporthe (Phomopsis) spp. on weeds as possible causative agents of sunflower stem cancer in the Vojvodina province. Helia, 17(20):39-48

Muntanola-Cvetkovic M, Mihaljcevic M, Petrov M, 1981. On the identity of the causative agent of a serious Phomopsis-Diaporthe disease in sunflower plants. Nova Hedwigia, 34(3/4):417-435

Muntañola-Cvetkovic, M., Vukojevic, J., Mihaljcevic, M., 1991. The systematic nature of the sunflower disease caused by Diaporthe helianthi. Canadian Journal of Botany, 69(7), 1552-1556. doi: 10.1139/b91-199

Nemeth, F., Princzinger, G., Vörös, J., 1981. New disease in Hungary. Magyar Mezogazdasag, 48, 10-11.

OEPP/EPPO, 2001. EPPO Standards PP 2/21 Good plant protection practice for sunflower. Bulletin OEPP/EPPO Bulletin, 31: 243-255

Olson, T. R., 2017. Managing Phomopsis stem canker of sunflower using improved diagnosis and quantification of the causal pathogens. South Dakota State University. 124 pp. http://openprairie.sdstate.edu/etd/1184

Pinochet, X., 1995. (Phomopsis et evaluation varie 'tale de la sensibilite'). In: Le Phomopsis du tournesol, [ed. by Le Page, R.]. Paris, France: CETIOM. 27-36.

Piven' VT, Dolzhenko EG, Slyusar' eL, 2000. Cyclachaena xanthiifolia - a potential alternative host of Phomopsis species. Zashchita i Karantin Rastenii^breve~, No.5:28-29

Regnault, Y., 1985. Preliminary observations on Phomopsis of sunflower. (Premières observations sur le phomopsis du tournesol). Bulletin CETIOM, (No. 92), 13-20.

Savotikov YuF, Smetnik AI, 1995. Manual of the pests, diseases and weeds of quarantine significance for the territory of the Russian Federation. Nizhnii Novgorod, Russia: Arnika, 143-145

Skripka, O. V., Shelukhin, V. I., Petina, V. V., Serebryakova, T. P., 1993. Phomopsis of sunflower. Zashchita Rastenii (Moskva), (No. 8), 24-25.

Slyusar' eL, Antonova TS, Bochkarev NI, 1998. On the spread of Phomopsis infection on sunflower. Zashchita i Karantin Rastenii^breve~, No. 1:33-35

Smetnik AI, Aleksandrov IN, Skripka OV, Izmalkova AG, 1998. Sunflower seeds as a way of preservation of Phomopsis infection. Zashchita i Karantin Rastenii^breve~, No. 1:35-36

Talukder, Z. I., Hulke, B. S., Marek, L. F., Gulya, T. J., 2014. Sources of resistance to sunflower diseasesin a global collection of domesticated USDA plant introductions. Crop Science, 54(2), 694-705. https://www.crops.org/publications/cs/abstracts/54/2/694 doi: 10.2135/cropsci2013.07.0506

Thompson, S. M., Tan, Y. P., Shivas, R. G., Neate, S. M., Morin, L., Bissett, A., Aitken, E. A. B., 2015. Green and brown bridges between weeds and crops reveal novel Diaporthe species in Australia. Persoonia, 35, 39-49. http://www.ingentaconnect.com/content/nhn/pimj doi: 10.3767/003158515X687506

Viguié, A., Vear, F., Labrouhe, D. T. de, 1999. Interactions between French isolates of Phomopsis/Diaporthe helianthi Munt.-Cvet. et al. and sunflower (Helianthus annuus L.) genotypes. European Journal of Plant Pathology, 105(7), 693-702. doi: 10.1023/A:1008715816205

Vrandecic, K., Jurkovic, D., Riccioni, L., Cosic, J., Duvnjak, T., 2010. Xanthium italicum, Xanthium strumarium and Arctium lappa as new hosts for Diaporthe helianthi. Mycopathologia, 170(1), 51-60. http://springerlink.metapress.com/link.asp?id=102966 doi: 10.1007/s11046-010-9289-2

Vörös J, 1988. Diaporthe helianthi. In: European Handbook of Plant Diseases. Oxford, UK: Blackwell, 315

Yang S, Berry RW, Luttrell ES, Vongkaysone T, 1984. A new sunflower disease in Texas caused by Diaporthe helianthi. Plant Disease, 68(3):254-255

Yang, S. M., Gulya, T. J., 1984. Groups of Diaporthe/Phomopsis isolates obtained from cultivated sunflower. Phytopathology, 74, 868.

Contributors

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22/08/19 Review by:

Febina Mathew, South Dakota State University, Brookings, SD, USA

Charles Block, Iowa State University, Ames, IA, USA

Robert Harveson, University of Nebraska-Lincoln, Scottsbluff, NE, USA

Thomas Gulya, USDA-ARS Northern Crop Science Laboratory, Sunflower and Plant Biology Research Unit, Fargo, ND, USA (Retired)

Mal Ryley, University of Southern Queensland, Toowoomba, QLD, Australia (Retired)

Susan Thompson, University of Southern Queensland, Toowoomba, QLD, Australia (Retired)

Samuel Markell, North Dakota State University, Fargo, ND, USA

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