Fábio Schreiber

By André Andres, Germani Concenço, Fábio Schreiber, Dirceu Agostinetto, Leandro Vargas, João Behenck, Giovanni Antoniaci Caputo and Ygor Sulzbach Alves

The intensive use of herbicides in agriculture has led to the appearance of resistant weed biotypes. Resistance is the inherited ability of a plant to survive following application of an herbicide dose which should be lethal. Morphophysiological weed traits help defining the risk to evolve resistance. These traits are not exclusive to the species but may be innate to botanical order, family, or genus. Four reference countries were screened about the nature of resistance—Australia, Canada, France, and the United States—and the data were used for predictions in the Brazilian scenario. Most weed species with resistant biotypes in the reference countries seem to be native to the continent. The most important botanical families with resistant biotypes in the reference countries were also among the first ones to develop resistance in these countries. There was a predominance of C3 species over C4 in the number of plant species with resistant biotypes in the reference countries. In Brazil, three orders are considered as high risk (Gentianales, Lamiales, and Solanales), besides the six already present. Furthermore, eight botanical families present superior risk to evolve resistance and for five of them (Caryophyllaceae, Polygonaceae, Rubiaceae, Convolvulaceae, and Solanaceae), resistance cases have not been reported to date in Brazil.

Part of the book: Herbicide Resistance in Weeds and Crops

By Germani Concenço, Patrícia Menegaz de Farias, Néstor Fabio Alzate Quintero, Fábio Schreiber, Leandro Galon, Michely Tomazi, Ivana Santos Moisinho, Mariane Camponogara Coradini, William Christofari Ceolin and André Andres

Phytosociological surveys have been applied to studies on agroecosystems, especially in relation to weed populations into arable fields. These surveys can indicate trends of variation of the importance of plant populations within a crop, and whether the variations are associated to agricultural practices adopted, which can be further used to support the development of weed management programs. However, to understand the applicability of phytosociological studies for weeds, it is necessary to understand the ecological basis and determine the most appropriate methods to be used when surveying arable fields. Therefore, the aim of the present chapter is to introduce a new approach of phytosociological survey to be used as a tool for the weed science. Throughout the chapter, this new approach is presented in details covering aspects related to methods for sampling and describing weed communities. The following sequence of steps is proposed as the most suitable for a weed phytosociological and association survey: (1) overall infestation; (2) phytosociological tables/graphs; (3) intra-characterization by diversity; (4) inter-characterization and grouping by multivariate analysis; and (5) weeds association through contingency tables.

Part of the book: Plant Ecology

By Ananda Scherner, Fábio Schreiber, André Andres, Germani Concenço, Matheus Bastos Martins and Andressa Pitol

The challenges for weed management have increased in rice cultivation due to the high number of cases of herbicide-resistant weeds, especially the widespread distribution of imidazolinone-resistant weedy rice. Therefore, there has been particular interest in preventive, physical, and cultural methods in recent decades. In this context, the adoption of the rice-soybean rotation is reported to be one of the most important factors for weed management in rice fields. Additionally, the use of a diversified crop rotation enables the implementation of a broader herbicide program, which is an important feature influencing weed population dynamics. Rice-soybean rotation has been adopted by farmers to control problematic weed species, reduce seed bank of troublesome weed species, and prevent rice grain yield and quality losses caused by its interference. This crop rotation scheme has brought several benefits when it comes to weed management; however, there are also some drawbacks when adopting this strategy such as the limited productivity of soybean and new weed species becoming problematic, such as Conyza species. Thus, this chapter explores the advantages and disadvantages of adopting crop rotation in Brazilian lowlands, and proposes a set of strategies to successfully implement crop rotation in lowland soils as a tool for weed management.

Part of the book: Rice Crop

By Fábio Schreiber, Ananda Scherner, André Andres, Germani Concenço and Francisco Goulart

Almost all plants are negatively affected by neighboring plants, which impose some degree of competition within the population, depending mainly on the quantity and quality of natural resources available in the environment. In rice cultivation, the occurrence of a high and diverse infestation of weeds results in high competition levels among the species. In addition, the high and growing number of cases about herbicide-resistant weeds, especially the widespread distribution of Imidazolinone-resistant weedy-rice and the high infestation of weeds belonging to the Echinochloa genus, has increased the competition levels within rice cultivation due to the lack of control. Therefore, the inclusion of rice cultivars with greater competitive ability represents a promising tool for weed management, since new cases of resistance to herbicides are often reported and alternative control strategies are scarce. The use of rice cultivars with a greater ability to suppress weeds can alleviate the competitive effect of these species, giving priority to the crop for the use of environmental resources due to the faster occupation of the ecological niches. Thus, this chapter aims to explore the competitive ability of rice cultivars against troublesome weed species, accounting for the role of their morphological and physiological traits as a function of environment-friendly crop practices.

Part of the book: Plant Competition in Cropping Systems