Analysis of the agronomic interest characteristics for the management of Conyza blakei, Conyza bonariensis, Conyza sumatrensis, and Conyza lorentzii

Abstract

Conyza genus includes herbs of ruderal habit, also referred to weeds in pastures, perennial crops, and no tillage crops. The insuitable use of herbicides, the incorrect identification of species, and the lack of monitoring, among others, explain the fact that Conyza species have become a growing problem in production systems under no tillage. Therefore, the knowledge of biology and the adaptive response to diverse cultural practices is paramount. Two of the most important characteristics to establish management guidelines are the height and growth stages of these species,since their herbicides sensitivity have been associated with these characteristics. The objective of this work was to analyze the results that affect the reproductive success (germination%, fecundity), and the most effective weed control time (height and determination of the phenological stages) of Conyza blakei, C. bonariensis, C. lorentzii and C. sumatrensis. Trials were conducted at the Agricultural Experimental Station of Balcarce, INTA, Argentina. We analyzed 35 individuals of each species. The germination % presented significant differences, being C. sumatrensis, the specie with the highest number of emerged seedlings. The phenological stages also showed differences, being C. bonariensis the species that began to elongate the stem earliest, the first in flowering, and the greatest fecundity. The senescence of the 4 species occurred within the first year of growth. The species with greater reproductive success would be C. bonariensis and C. sumatrensis, requiring the first earlier practices of controls.

Australia’s first case of glyphosate-resistant tall fleabane (Conyza sumatrensis) and alternative herbicide options for its control

“…These traits suggest that the sole reliance on glyphosate for tall fleabane control in fallows and glyphosate-resistant cotton crops in Australia may result in a rapid increase in resistant cases. Tall fleabane is a self-pollinated species, and wind-mediated dispersal of seeds could help in the spread of resistance from one field to another (Andersen 1993;Diez de Ulzurrun et al 2020;Hao et al 2009). A study in China concluded that autonomous seed production contributed significantly to the invasiveness of tall fleabane (Hao et al 2009).…”

“…In Australia, tall fleabane is present in all the states and territories, except the Northern Territory (AVH 2022). In addition to infesting fallow fields, it is a problematic weed in cotton (Gossypium hirsutum L.) and horticultural fields (Diez de Ulzurrun et al 2020;Everett 1990;Thebaud and Abbott 1995) in other countries.…”