Cultivar resistance and chemical, biological and fertilizer treatments for controling Botrytis leaf blight of onion
Botrytis leaf blight, caused by Botrytis squamosa, is an important disease of onion, mainly in the Southern region of Brazil. Studies on disease management that include host resistance, chemical, biological and alternative methods are scarce in the region. This work aimed to evaluate the effect of control treatments and 40 onion genotypes with varying resistance levels on disease management. Control treatments included seven fungicides, one biocontrol agent, and a calcium phosphite treatment. Among the genotypes, Ônix and Libório cv. exhibited the lowest levels of disease severity in the 2015 experiment, while the Bola Agroecológica, Preciosa, Ônix, and Super Agroecológica cv. were least affected in the 2016 experiment. Trifloxistrobin (75 g/ha) + tebuconazole (150 g/ha); boscalid (200 g/ha) + kresoxim-methyl (100 g/ha); and fluazinam (398.4 g/ha) best controlled the disease, while dicarboximides, Bacillus subtilis and phosphorus pentoxide (600 g/ha) + calcium (120 g/ha) did not differ from the control. We updated the data on host resistance to Botrytis squamosa and report for the first time the inefficacy of iprodione and procymidone for controlling Botrytis leaf blight in Brazil.
KeywordsAllium cepa Botrytis squamosa Chemical control Resistance
The authors would like to thank Edmar Bittencourt for the support during the fieldwork. This research was funded by: Epagri; SC Rural; CNPq (449218/2014-7).
- Boff P (1996) Avaliação da resistência de genótipos de cebola a Botrytis squamosa, na fase de muda. In: Reunião da Pesquisa na Cultura de Cebola no Mercosul, 1996, Ituporanga, Sc. [Anais...]. Epagri, Florianópolis p 33Google Scholar
- Brasil (2016) Agrofit- Sistema de Agrotóxicos Fitossanitários. Available in http://www.agricultura.gov.br/servicos-e-sistemas/sistemas/agrofit, 08/01/2016
- FRAC (2017) FRAC Code List© 2017: fungicides sorted by mode of action (including FRAC Code numbering). http://www.frac.info/docs/default-source/publications/frac-code-list/frac-code-list-2017-final.pdf?sfvrsn=fab94a9a_2. Accessed 18 Sept 2017
- Galván G, González PH, Reggio A (2004) Onion leaf blight caused by Botrytis squamosa in Uruguay and the differential response of local cultivars. Allium Improvement Newsletter 13:51–54Google Scholar
- Hancock JG, Lorbeer JW (1963) Pathogenesis of Botrytis cinerea, B. squamosa, and B. allii on onion leaves. Phytopathology 53:669–673Google Scholar
- IBGE (2016) Levantamento Sistemático da Produção Agrícola. Rio de Janeiro 29:1–79Google Scholar
- Lorbeer JW, Jares TW (1981) Field sampling patterns for determining the critical disease level for initiating fungicidal control of Botrytis leaf blight of onion. Phytopathology 71:238Google Scholar
- Nielsen K, Justesen AF, Funck Jensen D, Yohalem DS (2001) Universally primed polymerase chain reaction alleles and internal transcribed spacer restriction fragment length polymorphisms distinguish two subgroups in Botrytis aclada distinct from B. byssoidea. Phytopathology 91:527–533CrossRefPubMedGoogle Scholar
- Sutton JC, James TDW, Rowell PM (1983) Relation of weather and host factors to an epidemic of botrytis leaf blight in onions. Canadian Journal of Plant Pathology 5:256–265Google Scholar