Dados do Trabalho

Título

MODELO DE COX COM PREDITORES QUALITATIVOS PARA ANALISE DE PADROES TEMPORAIS DE MUDANÇA DE FASE EM INSETOS

Resumo

Larval stage duration (LSTD), the time interval (t) between egg eclosion and onset of pupal stage, is a key variable in entomological studies for evaluating treatment effects on insect development. This variable is a component of population growth rate in demographic studies, which are important to evaluate suitability of diets, chronical and sub lethal effects of pesticides or growth inhibitors on insect species. LSTD observations, measured in days, are referred to as ‘censored’ whenever the insect die before reaching pupal stage. In this work, we fit Cox model with qualitative predictors to evaluate the influence of host species (cowpea, soybean and weeds) on the time pattern of the onset of pupal stage of Chrysodeixis includens, represented by the cumulative distribution function of LSTD (F[t]=1- P[T>t]). C. includens is an important pest of cowpea, soybean, cotton and sunflower crops but also can survive in some weeds. We performed an exploratory LSTD analysis by fitting F[t] via Kaplan-Meier method and comparing the F[t] among treatments (species) by the Log-Rank test with Sidàk adjustment for multiple comparisons. Evidence of host plat effect on time pattern of pupal onset were quantified using a priori comparisons among F[t] performed via contrasts among Cox model parameters. Analysis were performed using LIFETEST and PHREG Procedures of the statistical software SAS/STAT®. The proposed methods allowed inferring that the host species cowpea contributes to greater larvae precocity when compared to the remaining species evaluated

Palavras-chave

Survival analysis, Cox model, larval development, insect life cycle