Data/hora: 16/06/2024 07:30:29

Biblioteca(s): | Epagri-Sede.
Data corrente: | 15/12/2016
Data da última atualização: | 15/12/2016
Autoria: | NESI, C. N.; SILVA, M. C. C. R.; BORSOI, F. T.; SCHMIZT, L.; WORDELL FILHO, J. A.
Título: | Phaeosphaeria leaf spot in maize under fungicide treatment.
Ano de publicação: | 2016
Fonte/Imprenta: | In: WORKSHOP BRASILEIRO DE EPIDEMIOLOGIA DE DOENÇAS DE PLANTAS, 5., 2016, Cruz das Almas. Resumos... Cruz das Almas: Embrapa Mandioca e Fruticultura, 2016.
Idioma: | Inglês
Conteúdo: | The Phaeosphaeria leaf spot (PLS) has been considered as one the most important foliar diseases of in maize in South Brazil. Thus, this study aimed to evaluate the progress of Phaeosphaeria leaf spot severity over time and along of canopy of maize plants with and without fungicide application. The severity was evaluated in a susceptible hybrid using 5 plants per plot (6 repetitions) without application and with 4 applications of the Trifloxystrobina + Prothioconazole fungicide. Severity assessments  were made at different stages of grain filling (15%, 35%, 75% and 92%), corresponding to R2 (blister stage), R3 (milk stage), R4 (dough stage) and R5 (dent stage) stages and in the ear insertion leaf (EL), in the first (EL+1) and in the second (EL+2) leaves above. The logistic model was adjusted as y = a/(1+exp((x-b)/c)), where 'y' is the observed severity, 'a' maximum asymptote; 'b' value of x in the point inflection and 'c' is a scale parameter. The model for observed severity in the i-th leaf (i = 1, 2 and 3) of the j-th plant (j = 1, 2, ..., 30) can be written as yij = aij/(1+exp((bij-x)/cij)) + &#949;ij, in which aij estimates the maximum severity (point inflection), bij estimates the grain filling stage where there is half of the maximum severity and &#949;ij are random errors associated with yijk (independent and identically distributed). Assuming the inclusion of the random effect of the plant in 'a' and 'b', the model is written as yij = (aij+z1ij)/(1+exp(((bij+z2ij)-x)/cij))+&#949;ij, where z1ij and z2ij are random effects parameters associated with 'a' and 'b', respectively. Data analyses were performed using the R statistical system and the add-on package 'nlme', comparing the models by AIC statistic. The estimates of the parameters model for EL, EL+1 and EL+2 were compared by contrasts, and between treatments observing the intervals with 95% confidence. Plants without fungicide there was no significant difference in severity between EL (79.0%), EL+1 (80.0%) and EL+2 (80.2%). The grain filling stage for half of the maximum severity increased as the leaf was farther from the ear (EL, 49.2%; EL+1, 53.0% and EL+2, 55.9%). With fungicide, only the severity of EL+1 (59.6%) differs from EL (67.5%), with 64.6% in EL+2. The grain filling stage where it was observed half of the maximum severity increased compared with EL (59.3%) only for EL+2 (69.5%) with 56.32% for EL+1. The fungicide use reduced around 11% the maximum severity in EL and 20% in EL+1. The grain filling stage for half of the maximum severity in treated plants increased only to the EL (up to 10%).
Palavras-Chave: | controle; mancha branca; Milho.
Categoria do assunto: | F Plantas e Produtos de Origem Vegetal
URL: | http://intranetdoc.epagri.sc.gov.br/producao_tecnico_cientifica/DOC_38734.pdf
Registro original: | Epagri-Sede (Epagri-Sede)
Exemplares: | Epagri-Sede - (100905-1) - UPC - PL - DD -  -  -  - DIS