Plant extracts and essential oils on the control of Alternaria alternata , Alternaria dauci and on the germination and emergence of carrot seeds ( Daucus carota L.)

Abstract

ABSTRACT: The present study aims to investigate garlic, pepper and coriander plant extract as well as neem and orange peel essential oil effective ness to control Alternaria alternata and Alternaria dauci and their efficiency during carrot seeds germination and emergence. A completely randomized design was used in three different experiments. The first experiment evaluated the effect of plant extracts and essential oils on the incidence of A. alternata and A. dauci . It was done by means of a factorial design applied to five treatments (garlic, pepper, coriander, and neem and orange peel essential oils) at three concentrations (10, 20 and 30%).They also evaluated the controls untreated and with fungicide (Thiram).The second experiment evaluated the effect of the treatment at30% concentration on the germination and emergence of seedlings assessed on trays, and in the third experiment, the presence of A. alternata and A. dauci on the pericarp, endosperm and on the embryo. A. alternata showed higher incidence than A. dauci. The garlic extract and the orange essential oil showed the potential to control A. dauci and A. alternata, because their lower concentrations were able to sufficiently reduce the incidence of these fungi and because they do not affect carrot seeds germination and emergence. A. alternata conidia were found on the embryo (8%), pericarp (17%) and endosperm (31%).RESUMO: O presente estudo teve por objetivo verificar a eficiência de extratos vegetais de alho (Allium sativum L.), pimenta dedo-de-moça ( Capsicum baccatum L.), coentro ( Coriandrum sativum L.), óleos essenciais de nim ( Azadirachta indica A. Juss.) e laranja ( Citrus sinensis L. (Osbeck)) no controle de A. alternata e A. dauci , bem como, sobre a germinação e emergência de sementes de cenoura. Foram realizados três experimentos com delineamento experimental inteiramente casualizado. No primeiro experimento, avaliou-se o efeito dos extratos e óleos essenciais vegetais sobre a incidência de A. alternata e A. dauci , em esquema fatorial com cinco tratamentos (alho, pimenta, coentro e óleos essenciais de nim e de laranja), em três concentrações (10, 20 e 30%), acrescido das testemunhas sem tratamento e com fungicida (Thiram). No segundo experimento, avaliou-se o efeito dos tratamentos a 30%, sobre a germinação e emergência de plântulas em bandejas e, no terceiro, a presença de A. alternata e A. dauci no pericarpo, endosperma e embrião. O fungo A. alternata apresentou maior incidência que A. dauci. O extrato de alho e o óleo essencial de laranja demonstraram potencial para o controle de A. alternata e A. dauci , pois, na menor concentração, reduziram satisfatoriamente a incidência desses fungos e foram inócuos a germinação e emergência de sementes de cenoura. Conídios de A. alternata foram identificados no embrião (8%), pericarpo (17%) e endosperma (31%).