Ecologia da mosca-branca, Bemisia tabaci (Gennadius) e de seus parasitóides em soja

• Autor(a) principal: Santos, Jardel Barbosa dos
• Data de Publicação: 2017
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da UFG
• dARK ID: ark:/38995/0013000006pcw
• Texto Completo: http://repositorio.bc.ufg.br/tede/handle/tede/7302
• topic: Efeito de bordas; Vegetação nativa; Parasitismo de mosca-branca; Edge effect; Native vegetation; whitefly parasitism; CIENCIAS AGRARIAS::AGRONOMIA

The patterns of parasitism and the influence of the edges between native vegetation and soybean crop on the population dynamics of whitefly were evaluated in twenty fields in the center-west of Brazil. Monitoring was carried out in two crop seasons, 2013/2014 and 2014/2015. The samplings were biweekly, in two field sites, one on the edge, 20 meters away from the native vegetation and another in the interior of the field, at least 400 meters from the edge. Adult populations of whitefly were monitored using yellow stick traps and whitefly nymphs and parasitized nymphs where counted in 30 soybean leaflets in the lower third of the plant per sampling point. Four species of whitefly parasitoids in soybean, Encarsia lutea, E. porteri, E. nigricephala and Eretmocerus mundus were identified. The species of greatest abundance was E.lutea, which was found in approximately 60% of parasitized nymphs. The rate of parasitism ranged from 6.2% to 46.5% in 2013/14 and from 3.6 to 50% in the next season. Whitefly parasitism is strongly correlated with host density and air temperature, being the first responsible for 98.6% of the explanation for the variability of whitefly parasitism in soybean. The population of the parasitoid increases with increasing host density, indicating a positive dense-dependent response. It was also observed that the population dynamics of the whitefly is affected by edge, period, the season and the field. Higher density of adult and whitefly nymphs was observed at the edge adjacent to natural vegetation, when compared to the interior of soybean crops. On average, 133.3 adults/traps and 6.6 whitefly nymphs/leaflets were observed at the edge adjacent to the native vegetation within the fields. However, it was not observed higher density of the parasitism at the edge adjacent to the native vegetation than inside the soybean field, pointing out that the current conditions of native vegetation remnants do not contribute as reservoir of parasitoids. Thus, the border adjacent to the native vegetation has not contributed to the establishment of the natural control of the pest. The differential effects of the border on the population density of the pest and its parasitoids indicate that the edges should be prioritized in the monitoring of the whitefly and that to increase the rates of parasitism of the pest, fragments of natural vegetation need to be conserved and restored.