Inibição da germinação de sementes de Conyza canadensis utilizando extratos de plantas medicinais

Conyza species, popularly known as horseweed, are invasive weeds and considered a big challenge for Brazilian agriculture. Many seeds are produced, easily dispersed and together with impacts of herbicide-resistant, they are some of the weeds most difficult to control. In Brazil, Conyza canadensis, belonging to this genus, shows glyphosate resistance and multiple herbicide resistance are observed in others countries. Weed control is important in agriculture and new strategies shoud be developed in order to contain these plants. In this context, studies with allelopathy have shown a promising alternative. The objective of this study was to evaluate the allelopathic effect and possible bioherbicida potential of plant extracts from white “ipê” (Tabebuia roseoalba), bushy matgrass, (Lippia alba) and false pepper (Schinus molle) on the weed C. canadensis seeds. The aqueous extracts were prepared by infusion at concentrations of 1 and 10%. The ethanolic extracts were obtained in a Soxhlet apparatus, followed by solvent evaporation. Subsequently, these extracts were diluted with distilled water at concentration of 1%. Only distilled water was used as control. The analyzed variables for all tests were germination percentage (%G) and germination speed index (GSI). The aqueous and ethanolic extracts (both 1%) inhibited the %G and showed a delay in germination. All 10% aqueous extracts, except those obtained from Tabebuia sp. leaves, affected the seeds germination. The alcoholic extracts were more effective in inhibiting the germination than the aqueous one. All extracts showed allelopathic and herbicide potential on C. canadensis seeds. The alcoholic extract of false pepper showed greater potential for bioherbicides studies.