Avances en la exploración de la ecología de malezas para un manejo sostenible. Caso banano.

The weed community associated with agricultural systems undergoes changes in its diversity, composition and abundance due to climatic variations, edaphic properties, crop cycles, and mainly, management practices. These changes can be expressed by the arrival of new species to the community, the disappearance of some pre-existing species or the evolution of biotypes with greater competitive capacity, affecting the stability of the system. For these reasons, it is necessary to define adequate management strategies based on ecological principles, i.e., to recognize weeds as members of the agroecosystem, to understand the behavior of their communities, dynamics of change, including evolutionary aspects and distribution, and also to analyze their potential to provide different ecosystem services. Weed ecology deals with the study of the interactions between weeds and the environment, with special emphasis on the adaptive mechanisms that allow them to survive in agriculturally disturbed environments. Such studies may focus on individual organisms, groups of individuals of the same species (population) or groups of concurrent populations at the community level. Under this approach, which is assuming an increasingly prominent role in weed science, we have approached the study of the flora associated with banana crops in the department of Magdalena, where the persistence of highly competitive species and restrictions on the use of pesticides has attracted the attention of banana growers, who hope to improve weed management to comply with international Fair Trade policies and ensure profitable and sustainable production. In this dissertation I present the advances achieved in the study of the ecology of plant communities associated with banana crops, which have allowed us to understand their attributes and dynamics of changes, fundamental to define adequate management practices. Previous efforts aimed at identifying species potentially usable as cover crops in commercial banana plantations, allowed us to know the plant complex associated with the plantations1, becoming a reference to observe changes in the weed complex over time. Recent studies of the flora associated with the crop carried out in the four production zones in the department determined a heterogeneous floristic composition, represented by 204 species belonging to 143 genera and 54 families. Poaceae, Fabaceae and Asteraceae were the families with the greatest specific richness. Species richness was found to be similar among the four production areas, while community composition varied. In general, the weed complex was characterized by a greater number of perennial grasses, with a predominance of native species. In all areas there was the presence of species reported as weeds of worldwide importance, some of them hosts of crop pests and diseases, highlighting the presence of several species that did not appear as weeds in the region. The phytosociological analysis of the plant communities associated with the crop showed that the Commelinaceae family was the most ecologically important, in terms of infestation levels, followed by Poaceae and Cyperaceae. The species with the highest importance index were Commelina erecta, Axonopus compressus, Melothria pendula and Murdannia nudiflora. It was also possible to determine that the structure and diversity of the weed community differed between zones and by the effect of the control method used on the farms. Few species were very abundant and frequent, which indicated low diversity. Considering the field observations related to the loss of sensitivity of some weeds to glyphosate, as well as their prevalence in the plantations, the evolution of the weed community was evaluated by identifying biotypes resistant to this herbicide most frequently used on the farms. The results confirmed herbicide tolerance in populations of Commelina erecta and Syngonium podophyllum and resistance in populations of Erigeron bonariensis. The invasion risk analysis for the early detection of introduced weeds that are potentially risky due to their invasiveness, made it possible to categorize 24 species associated with the crop as high invasion risk, which suggests taking actions for the prevention, management and control of these weeds to avoid their spread in banana plantations and other surrounding ecosystems. These studies have made it possible to understand that the flora associated with the banana agroecosystem in the department of Magdalena presents a dynamic of change on a temporal and spatial scale, influenced by environmental factors specific to each production zone, the heterogeneity of the landscape and the weed control practices used on the farms, determining changes in the composition, structure, diversity and evolutionary aspects of the communities at the regional and local levels. The ability of the most important species to adapt to different environmental conditions, as well as to reproduce sexually and vegetatively, would explain the level of infestation of these species in the plantations. Likewise, the repetitive use of a single weed control method explains the dominance and prevalence of a few species. The confirmation of glyphosate tolerant and resistant populations on farms where the herbicide has been applied continuously for at least ten years as the only control method demonstrates that selection pressure has been generated leading to the evolution of biotypes with greater competitive ability. The potential use as cover for some species, in addition to expanding the options for control tactics, can provide ecological services, e.g., reducing soil erosion. These advances support the need to diversify the techniques used for weed control, seeking integrated management for crop sustainability. In general, we must understand that weed communities change rapidly and adapt to management practices, therefore, their assistance in agricultural systems must be permanent. [ABSTRACT FROM AUTHOR]