Controle alternativo da podridão seca de caule e raiz da graviola (Anonna muricata L.) causada por Lasiodiplodia theobromae (Pat.) Griffon & Maubl no estado de Alagoas

Abstract

The production of soursop stands out in Brazil, country which is also one of the biggest soursop producers. But one of the main problems that have limited this production is the emergence of diseases as dry rot of trunks and roots (Lasiodiplodia theobromae). This study focuses on the analysis of the usage of natural products as Trichoderma sp. and fungicide to control dry rot of the stem and roots of soursoptree, as well as the effect of the treatment in soursop seeds. Some compounds as Citronella oils (Cimbopogon nardus), Peppermint (Mentha piperita) and Lemon Eucalyptus (Eucalyptus citriodora Hooker M.), at concentrations of 25, 50, 75 and 100 μL.mL-1, and vegetables extracts as Garlic (Allium sativum L), Onion (Allium cepa) and Ginger (Zingiber officinale), at concentrations of 10, 20, 30 and 40%, as well as Mancozeb, at concentrations of 1, 2, 3 and 4 g.L-1 were tested. All compounds were sterilized in a laminar flow cabinet under UV light for 30 minutes and added to PDA medium flux for subsequent measurements of mycelial growth of the pathogen. The best in vitro test treatments were chosen for this analysis and the vegetables extract samples and fungicide were performed in the treatment of seedlings at periods of 7 days, the plants treated with fungicide were sprayed up 25 mL per plant and brushed with fungalpast at a concentration of 3 g.L-1. 400 seeds were collected of healthy fruits in a planting area for pathological analysis, they were submitted to treatments with and without disinfection with sodium hypochlorite 1%, oils, vegetables extracts, fungicide and 5% formaldehyde. For in field experiment were used treatments consisting of 5% formaldehyde, Trichoderma sp. (12, 24 and 36 g), 5% formaldehyde + Trichoderma 12g, 5% formaldehyde + Trichoderma 24g, formaldehyde 5% + Mancozeb 36g and Trichoderma (3g.L-1), these were used to control and determine the effects of the treatments in disease incidence (% of diseased plants). The 10% garlic extract controlled the in vitro growth of L. theobromae. The onion and ginger extracts were not able to control the fungus at the tested dosage. Citronella oil, eucalyptus and peppermint at the lowest dosage (25 μL) controlled growth of L. theobromae, and the eucalyptus and citronella showed phytotoxicity to plants. The Treatment of soursop seeds with sodium hypochlorite 1% significantly reduced the incidence of fungus, as well as the seeds microbiolization with Trichoderma sp. was feasible to controlling endophytic fungi. The usage of Trichoderma sp. and formaldehyde at 5% were efficient in controlling the dry rot in soursop seedlings, reaching 100% of disease control.