Efeito da casca de mandioca no controle da podridão radicular causada por Phytophthora sp. em mandioca de mesa (Manihot esculenta Crantz) var. Rosinha em ambiente irrigado

Abstract

Cassava is one of the most consumed crops around the world, behind only of corn and wheat. Originate from tropical regions and adapted to low fertility soils and water availability. Its main utility is on human and animal feeding, being its roots consumed in natura or processed for flour and starch manufacture, very appreciated on typical and regional dishes of regions North and Northeast of Brazil. Nigeria is one of the world’s largest producer, and recently Brazil has been ranking fourth, below Indonesia and Thailand. In Brazil, Pará stands out being the number one on production of cassava and its flour and Parana ranks in the manufacture of starch. Bahia is the largest producer, whilst Alagoas ranks 7th in cropped area and second in productivity on northeast region. The use of irrigation on sweet cassava crops contributes to the good development during the first five months of this plant, although when badly dimensioned on infested areas Phytophthora sp cause loses, being wilting and drying the main symptoms caused in the shoot system and the soft rot on mature roots. The aim of this study was to evaluate the effect of the addition of cassava's peel in the control of rot root caused by Phytophthora sp. on sweet cassava (Manihot esculenta Crantz) var. Rosinha in irrigated environment. Were performed two experiments at the Plant Pathology Laboratory on the Center of Agricultural Sciences of the Federal University of Alagoas: In the first it was observed the pathogenicity of the isolated and was evaluated the effect of the cassava peel's aqueous crude extract in the growth of Phytophthora sp. in vitro in the determination of the dose of cassava peel's aqueous crude extract under the environment capable of inhibit the pathogen mycelial growth; were evaluated the effect of the addition of the ground cassava peel on the control of Phytophthora sp. in sweet cassava (M. esculenta) var. Rosinha under different irrigation blades in greenhouse in the percentage of plants with no symptoms, root dry matter, total matter and water use efficiency; in 42 days old plants cultivated in pots with infested soil. In the second experiment it was used the results obtained from the doses of CM and Li from the first experiment in relation to the chemical treatment and non treated under the condition of infested and non infested soil evaluating the effect of ground cassava peel incorporation in the growth and control of root rot during the sweet cassava's rooting (M.esculenta), to field level, at IFAL - Satuba Campus, under fresh matter and dry root, dry matter, plant heigh, number of roots and harvest index.