Leveillula taurica

Pest (common name): 
Powdery mildew
Pest type: 
Fungus
Hosts:
Garlic, Onion, Tomato
Biological characteristics: 

Taxonomic position: Domain: Eukaryota; Kingdom: Fungi; Phylum: Ascomycota

Description: Powdery mildew is caused by Leveillula taurica (teleomorph) and Oidiopsis taurica (anamorph). This fungus can attack the crops at any time of their development; however, the most serious attacks occur on mature leaves. At the beginning, there are light green to bright yellow, somewhat angular, spots, irregularly distributed on the leaf surface. Later, there appears a necrotic brown area that grows larger. The leaf can die and fall, thus causing defoliation. In high humidity conditions it is possible to detect the fruitings of the fungus on the underside of the spot. These have the appearance of a dim whitish mold. It must be observed that the necrosis can bear concentric rings, as is the case with Alternaria solani, thus mistaking one fungus for the other if the fruitings are not observed with care.
L. taurica is a biotroph fungus and, in order to survive, needs a living plant or the cleistothecia (sexual fructification bodies), which, in Argentina, are to be found only in artichokes.
The fungus can be found on weeds such as Sonchus oleraceus and Solanum sisymbrifolium, among others. Some fungus strains are very specific; others are highly polyphagous.

The conidia of L. taurica are windborne and usually fall on leaves where they can germinate under temperature conditions ranging between 10 and 35 ºC. Optimal conditions are a temperature of 26 ºC and a relative humidity of about 70%. However, it seems that the environmental conditions do not play a significant role in the epidemiology of the disease. The conidia germinate with a short germinative tube that penetrates the stomata. They later grow intercellularly in the mesophyll of the plant. The fruitings emerge through the stomata.

Bibliography:
Mitidier, M.; Strassera, M. E.; Amoia, P. ; Martínez Quintana, O. 2010. Evaluación de fungicidas para el control de oidiopsis (leveillula taurica (Lév.) Arn.) en el cultivo de pimiento bajo cubierta. Instituto Nacional de Tecnología Agropecuaria (INTA); Estación Experimental Agropecuaria San Pedro; Horticultura Argentina 29(68). Page/s: 5 - 9. URL: http://www.inta.gov.ar/sanpedro/info/doc/2010/mm_1002re.htm. Checked on: 18/01/2011. Hosts: Onion; Tomato - Reference: 364.
Brandán de Antoni, E. Z.; González, A. G.; del Carmen Seco, E. 2009. Tomate destinado a la industria. Universidad Nacional de Catamarca, Facultad de Ciencias Agrarias, Cátedra de Horticultura y Economía Agraria. Page/s: 35. ISBN: 978 - 987 - 1341 - 77 - 1. URL: http://www.editorial.unca.edu.ar/Publicacione%20on%20line/CUADERNOS%20DE%20CATEDRA/Ana%20Gabriela%20Gonzalez/Tomate%20Industria%20UNCa%202009%20_Matdidactico%20Brandan_Gonzalez.pdf. Checked on: 30/11/2010. Host: Tomato - Reference: 343.
Argerich, C.A.; Lorenzo, M.G.; Aquindo, M.S.; Navarro, A.P.; Angelelli, H.; Gamarra Luque, L.; Muzaber, J.; Álamo, M.; Guevara, P.; Daruich, J.P. 2008. Ensayos regionales de variedades precoces y tardías campaña 2007-2008. Instituto Nacional de Tecnología Agropecuaria (INTA); Estación Experimental Agropecuaria - La Consulta; Asociación Tomate 2000. Page/s: 11. URL: http://www.inta.gov.ar/laconsulta/info/documentos/Tomate/2007%20-%202008/L-Regionales%2008.pdf. Checked on: 20/1/2011. Host: Tomato - Reference: 430.
Colombo, M.; Obregón, V. 2008. Horticultura General: Consideraciones de cultivo y manejo. VII: Sanidad de los cultivos hortícolas. Instituto Nacional de Tecnología Agropecuaria (INTA); Estación Experimental Agropecuaria - Bella Vista; Centro Regional Corrientes. Page/s: 51-65. ISSN 1515-9299. URL: http://www.inta.gov.ar/bellavista/info/documentos/hortalizas/ST24.pdf. Checked on: 20/08/2010. Host: Tomato - Reference: 60.
Piccolo, R.J. 2007. Enfermedades micológicas y bacterianas del ajo (Allium sativum). Instituto Nacional de Tecnología Agropecuaria (INTA); Estación Experimental Agropecuaria - La Consulta; Curso de producción de ajo - posgrado de horticultura; Universidad Nacional de Cuyo - 11 de abril de 2007. Page/s: 1 - 27. URL: http://www.inta.gov.ar/laconsulta/info/indices/tematica/ajo/Doc%20084%20enfermedades%20del%20ajo.pdf. Checked on: 20/09/2010. Host: Garlic - Reference: 300.
Miltidieri, M.; Polack, L.A. 2005. Guía de monitoreo y reconocimiento de plagas, enfermedades y enemigos naturales de tomate y pimiento. 8. Guía de reconocimiento de enfermedades en tomate y pimiento. Instituto Nacional de Tecnología Agropecuaria (INTA); Estación Experimental Agropecuaria - San Pedro. Page/s: 12. URL: http://www.inta.gov.ar/sanpedro/info/doc/2005/mm_0506enf.htm. Checked on: 18/10/2010. Host: Tomato - Reference: 219.
Polack, A.; Mitidieri, M. 2002. Producción de tomate diferenciado. Protocolo preliminar de manejo integrado de plagas y enfermedades. Instituto Nacional de Tecnología Agropecuaria (INTA); Estación Experimental Agropecuaria San Pedro; Información para extensión - Protección Vegetal n°20. Page/s: 18. ISSN: 0327 - 3245. URL: http://www.inta.gov.ar/sanpedro/info/doc/pdf/polack_protocolo_mip_pdf.pdf. Checked on: 18/01/2011. Host: Tomato - Reference: 363.
Mazzanti de Castañon, M.A.; Cundom, M.A.; Cabrera de Alvarez, M.G. 1994. Enfermedades en cultivos protegidos de tomate, pimiento y berenjena, en el nordeste argentino. Hort. Arg. 13(34-35): 1-8. may.-dic. 1994. Page/s: 8. Host: Tomato - Reference: 347.

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