Essential oils for rust control on coffee plants

Abstract

Rust is considered the most important disease in coffee because it causes severe defoliation in plants and, consequently, reduction in productivity. This study evaluated the in vitro effect of essential oils of cinnamon, citronella, lemongrass, clove, tea tree, thyme, neem and eucalyptus on the germination of urediniospores of Hemileia vastatrix; the effectiveness of these oils to control rust on seedlings of coffee cultivars Catucaí 2SL, Catuaí IAC 62 and Mundo Novo 379/19 in the greenhouse; and the effect of more promising oils on urediniospores of H. vastatrix by transmission electron microscopy (TEM). All the essential oils inhibited the germination of urediniospores with increasing concentrations. All oils promoted partial control of the disease in the greenhouse. However, the oils of thyme, clove and citronella, at a concentration of 1000 µL L -1 , were most effective in controlling the disease on cultivars Catucaí 2SL, Catuaí IAC 62 and Mundo Novo 379/19, respectively. The images generated in TEM showed that urediniospores exposed to oils of clove, citronella and thyme promoted cellular disorganization and cytoplasmic vacuolization, which was more pronounced in urediniospores exposed to citronella oil. The oils of thyme, clove and citronella are promising for the control of rust in coffee.Index terms: Hemileia vastatrix, alternative control, transmission electron microscopy. RESUMOA ferrugem é considerada a doença de maior importância no cafeeiro, pois causa acentuada desfolha nas plantas e, consequentemente, redução na produtividade. Este trabalho avaliou o efeito in vitro de óleos essenciais de canela, citronela, capimlimão, cravo-da-índia, árvore-de-chá, tomilho, nim e eucalipto na germinação de urediniósporos de Hemileia vastatrix; a eficácia desses óleos no controle da ferrugem em mudas de cafeeiro das cultivares Catucaí 2SL, Catuaí IAC 62 e Mundo Novo 379/19 em casa de vegetação; e o efeito dos óleos mais promissores sobre urediniósporos de H. vastatrix por meio de microscopia eletrônica de transmissão (MET). Todos os óleos essenciais inibiram a germinação dos urediniósporos com o aumento das concentrações. Todos os óleos promoveram controle parcial da doença em casa de vegetação. No entanto, os óleos de tomilho, cravo-da-índia e citronela, na dose de 1000 µL L -1 , foram os mais eficazes no controle da doença nas cultivares Catucaí 2SL, Catuaí IAC 62 e Mundo Novo 379/19, respectivamente. Nas imagens geradas em MET, observou-se que urediniósporos expostos aos óleos de cravo-da-índia, citronela e tomilho apresentaram desorganização citoplasmática e vacuolização celular, sendo esta mais pronunciada em urediniósporos expostos ao óleo de citronela. Os óleos de tomilho, cravo-da-índia e citronela são promissores no controle da ferrugem em cafeeiro. Termos para indexação:Hemileia vastatrix, controle alternativo, microscopia eletrônica de transmissão.

Antibacterial activity of essential oils on Xanthomonas vesicatoria and control of bacterial spot in tomato

“…The essential oils of tea tree, eucalyptus, and citronella promoted control of the disease similar to that of the fungicide. Furthermore, Pereira et al (2012) observed protection of 54.3% when using clove oil (0.1%) against coffee plant rust, which is similar to the result found in the present work.…”

“…In a field experiment with Asian soybean rust and in a greenhouse experiment with coffee plant rust, respectively, Medice et al (2007) and Pereira et al (2012) obtained results similar to the ones observed in the present study. The essential oils of tea tree, eucalyptus, and citronella promoted control of the disease similar to that of the fungicide.…”

Thymus vulgarisessential oil and thymol againstAlternaria alternata(Fr.) Keissler: effects on growth, viability, early infection and cellular mode of action

“…Such metabolites may serve as promising sources of additional products to control plant disease. Consequently, much research has been conducted concerning the capability of natural products against plant pathogens . Much research has demonstrated the effectiveness of essential oils (EOs) against plant pathogens, and Thymus vulgaris and Thymus spp.…”

“…Consequently, much research has been conducted concerning the capability of natural products against plant pathogens . Much research has demonstrated the effectiveness of essential oils (EOs) against plant pathogens, and Thymus vulgaris and Thymus spp. have regularly been shown to perform well, occasionally presenting levels of control comparable with those achieved with commercial fungicides .…”

“…Much research has demonstrated the effectiveness of essential oils (EOs) against plant pathogens, and Thymus vulgaris and Thymus spp. have regularly been shown to perform well, occasionally presenting levels of control comparable with those achieved with commercial fungicides . Although examples relating to the composition of active substances obtained from plant EOs against microorganisms in food are easily found, such studies are rarely found for plant‐pathogenic fungi .…”