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Field persistence of Bacillus thuringiensis Berliner (Bacillales: Bacillaceae) biopesticides in the field

Grant number: 14/23183-6
Support type:Scholarships in Brazil - Scientific Initiation
Effective date (Start): April 01, 2015
Effective date (End): March 31, 2016
Field of knowledge:Agronomical Sciences - Agronomy
Principal Investigator:Ricardo Antonio Polanczyk
Grantee:Laís Fernanda Moreira
Home Institution: Faculdade de Ciências Agrárias e Veterinárias (FCAV). Universidade Estadual Paulista (UNESP). Campus de Jaboticabal. Jaboticabal , SP, Brazil

Abstract

A major obstacle to the use of biopesticides based on Bacillus thuringiensis (Bt) is the low field persistence resulting in reapplication to ensure satisfactory control of the pest control cost increases. Thus, the goal of this research is to evaluate the persistence of three Bt biopesticides in the field using a half dose, recommended dose and double the recommended dose for two crops of corn. Each dose will be tested in 45 maize plants (distributed in three replicates) in the growth stage v3-v4. Three plants will be chosen randomly on each repetition and each plant will be evaluated six leaves at the top (similar orientation and no shading). Two leaf disks (2 cm diameter) with a metal punch are withdrawn at various intervals between 3 and 72 hours after treatment application. Witness in the leaves of the plant will be highlighted and placed in laboaratory chamber (dark) where they will be removed leaf discs as described above. Leaf discs (pair) sampled in each leaf and each period will be immersed in distilled water in the laboratory, shaken and subjected to thermal shock. Subsequently, an aliquot of the suspension is applied 5¼L 5 points in a petri dish with culture medium. After 48 hours will assess the number of viable spores and the data subjected to analysis of variance (ANOVA) and the means are compared by Tukey test at 5%. The half life of viable spores will be calculated according to Pinnock et al. (1971) and comparison of the method overlapping confidence intervals (P = 0.05) is used.