Biologia e manejo da planta daninha Borreria densiflora DC.

Abstract

Biology and management of the weed Borreria densiflora DC. The weed vassourinha-de-botao (Borreria densiflora DC.) has been presenting increase in its infestation in areas cultivated with sugarcane and soybean, respectively in Maranhao and Goias states and north of Tocantins state, Brazil. Field observations have reported the control deficiency of this species, when it occurs in advanced growth stage. Thus, this research was conducted with the objective of classify botanically the weed, analyze the light and temperature influence on the germination of this species, its growth, development and reproductive structures, its susceptibility to herbicides in pre and post conditions, as well as the influence of the interaction between seed burial and the presence of crop residue in different amounts in the soil surface on the emergence of this weed. The botanical classification of vassourinha-de-botao was done in the Exact and Natural Sciences College-UNNE / IBONE, Argentina; the experiment that evaluated germination under different conditions was conducted in the Seeds Analyzes Laboratory, of the Crop Science Department of USP / ESALQ, and all the other experiments were carried out in the same department, between 2006 and 2007. It was concluded that the weed vassourinha-de-botao is the species Borreria densiflora DC. and it belongs to Rubiaceae family. Related to germination, it was observed that B. densiflora DC. is preferencial positive photoblastic, since its germination is favored by presence of light, responding differently to the studied light and temperature conditions. The highest germination rates and speeds of germination were reached in presence of photoperiod condition (12h), under the constant temperatures 30ºC and 35ºC and the alternated 20-30ºC. Basically, there was not germination in the constant dark condition. About the growth and development, it was observed that the weed Borreria densiflora DC. is a species with slow initial growth, with a simple perennial life cycle, presenting a big increment in the variables total dry biomass, relative growth and liquid assimilation rates between 26 and 36 days after transplanting (DAT). At the end of the experiment, the stems appear as the most participative compartments in the photosynthate partition by Borreria densiflora DC. This species is able to produce, in average, 93,090 seeds per plant. Related to the chemical management of Borreria densiflora DC., the majority of the herbicides provided controls considered adequate, except clomazone and MSMA, in pre and post-emergence conditions, respectively. Therefore, many herbicide options and mix of herbicides can be recommended to the management of the weed Borreria densiflora DC., since in pre-plant to pre and post-emergence. The study about the influence of the interaction between seed burial and presence of dry sugarcane residue in the soil surface on the emergence of this species demonstrated to exist interaction between those two tested factors, being that the bigger depth in the soil and amount of dry sugar...

A new variety of the weed Borreria densiflora DC. (Rubiaceae)

“…In Brazil, Borreria densiflora DC. has been reported as a weed recently (Martins 2008), and its taxonomic classification was not done at the intraspecific level. B. densiflora DC.…”

“…To date, this information is lacking for the studied weed in this research. Recent field observations have reported that vassourinha de botão is occurring in high infestations in soybean and sugarcane crops in northern and north‐eastern Brazil and is presenting difficulty in its management, mainly by chemical means, when it occurs in more advanced growth stages (Martins 2008). This species belongs to Rubiaceae, and is a member of the genus Borreria G. Mey.…”

Germinação de sementes de Conyza canadensis e Conyza bonariensis em diferentes condições de temperatura e luminosidade

“…Conhecendo a amplitude de temperatura em que as sementes de uma planta daninha germinam, é possível prever as regiões que seriam potencialmente colonizadas por essa espécie, bem como as épocas do ano em que seu estabelecimento teria maior sucesso (Martins, 2008).…”