No abstract

Efficiency and compatibility of Trichoderma spp. and Bacillus spp. isolates on the inhibition of Sclerotium cepivorum Eficiência e compatibilidade de isolados de Trichoderma spp. e Bacillus spp. na inibição de Sclerotium cepivorum

Bidens pilosa and B. subalternans are highly noxious herbaceous neotropical asteraceous weeds. A survey of fungal pathogens associated with these two species was undertaken in Brazil, aimed at finding natural enemies in order to establish the potential for introducing novel specific pathogens from other regions of the world, as classical biological control agents. Ten fungal species were found associated with both B. pilosa and B. subalternans, namely: Cercospora bidentis, C. maculicola, Entyloma bidentis, E. compositarum, E. guaraniticum, Neoerysiphe cumminsiana, Plasmopara halstedii, Podosphaera xanthii, Uromyces bidentis, and U. bidenticola. Three other species were found solely associated only with B. subalternans: Colletotrichum bidentis, Pseudocercosporella bidentis and Sphaceloma bidentis. Pseudocercosporella bidentis is described herein as new to science.

Stromatinia cepivora is one of the major pathogens of Allium species worldwide. Assuming that substances produced by plants may be used in the management of this pathogen, the effect of plant extracts and essential oils on the mycelial growth and germination of S. cepivora was assessed in this study. The fungus was grown on PDA medium with aqueous and ethanolic extracts (20 %, m:v) of mentrasto, rue, ginger, false saffron, garlic and citronella at the concentrations of 1 or 10 mL L -1 and the essential oils of citronella, rosemary, neem and Corymbia citriodora at 100, 200, 400, 800 or 1,200 µL L -1 . None of the plant extracts reduced the germination of the sclerotia. All aqueous extracts at 10,000 µL L -1 reduced the growth of the fungus from 28.0% to 53.5%. At the 1,000 µL L -1 , the ethanolic extracts of ginger, citronella, rue and false saffron reduced the mycelial growth of the pathogen up to 45.1 %, especially the extract of ginger. The essential oils of all the plants suppressed the mycelial growth of S. cepivora at 800 and 1,200 µL L -1 , especially the citronella and rosemary oils at 1,200 µL L -1 , which caused 100% of inhibition. 5 % of sclerotia germinated in PDA containing the oils at 1,200 µL L -1 , regardless the plants. The extracts of mentrasto, rue, ginger, false saffron and citronella and especially the essential oils of citronella, rosemary, neem and C. citriodora at 1,200 µL L -1 have substances that inhibit the growth of S. cepivora.Additional keywords: Allium spp.; alternative control; white rot. ResumoStromatinia cepivora é um dos principais patógenos de espécies de Allium em todo o mundo. Partindo do pressuposto de que substâncias produzidas por plantas podem ser usadas no manejo desse patógeno, o efeito de extratos vegetais e de óleos essenciais sobre o crescimento micelial e a germinação de S. cepivora foi avaliado neste estudo. O fungo foi cultivado em BDA com extratos aquosos e etanólicos (20%, m: v) de mentrasto, arruda, gengibre, falso-açafrão, alho e citronela, nas concentrações de 1 ou 10 mL L -1 e os óleos essenciais de citronela, alecrim, nim e eucalipto citriodora, a 100; 200; 400; 800 ou 1.200 µL L -1 . Nenhum dos extratos de plantas reduziu a germinação dos escleródios. Todos os extratos aquosos a 10.000 µL L -1 reduziram o crescimento do fungo, variando de 28,0% a 53,5%. Na concentração de 10.000 µL L -1 , os extratos etanólico de gengibre, citronela, arruda e falso-açafrão reduziram o crescimento micelial do patógeno até 45,1%, especialmente o extrato de gengibre. Os óleos essenciais de todas as plantas suprimiram o crescimento micelial de S. cepivora a 800 e 1.200 µL L -1 , especialmente a citronela e os óleos de alecrim, a 1.200 µL L -1 , que causaram 100% de inibição, 5% dos escleródios germinados em BDA contendo os óleos na concentração de 1.200 µL L -1 , independentemente da planta. Os extratos de mentrasto, arruda, gengibre, açafrão e falsa-citronela e, especialmente, os óleos essenciais de citronela, alecrim, nim e eucalipto citriodora, em 1200 µL L -1 , têm...

A leaf blight was observed on Costus spiralis in an experimental area in the campus of the Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil. Morphology and ITS sequences placed the fungus associated with the disease in Pyricularia grisea. Pathogenicity was demonstrated. This is the first record of P. grisea on Costus spiralis worldwide.