Differential Susceptibility of <i>Conyza bonariensis</i> Biotypes to Glyphosate and ALS-Inhibiting Herbicides in Argentina

Abstract

The aim of this study was to compare control of three stages biotypes (rosette, bolting, and reproductive stage) of Conyza bonariensis glyphosate susceptible biotype (S) and tolerant biotype (T) to glyphosate with glyphosate and mixtures of acetolactate synthase (ALS)-inhibiting. For glyphosate, the dose-response curves confirmed that injury of the biotype T relative to biotype S was significantly lower for both rosette and bolting stages. Resistance index (RI) for this herbicide was approximately 4 for both weed stages. At bolting, for both biotypes doses much higher than the recommended dose were required. For acetolactate synthase (ALS)-inhibiting herbicides, at the rosette stage, control of both biotypes was excellent with doses significantly lower than the recommended rate. All herbicides within this group showed a very low I50 relative to the recommended rate. These results indicate that biotypes difficult to control with glyphosate at the rosette and bolting stage may be controlled using acetolacte synthase (ALS)-inhibiting herbicides. Control for the reproductive stage was poor. A management program based on the combination of glyphosate with pre-and post-emergence acetolactate synthase (ALS) herbicides may be effective to control the weed.

Monitoring Glyphosate- and Chlorimuron- resistant Conyza spp. Populations in Brazil

“…The doses used in our research (960 g ha -1 for glyphosate and 20 g ha -1 for chlorimuron) have shown to be able to discriminate S and R populations in the three Conyza spp. species (Kruger et al 2009, Santos et al 2014a, Puricelli et al 2015.…”

Dormancy, a critical trait for weed success in crop production systems

“…Both cohorts were controlled easily under conventional tillage: the autumn cohort was killed by the tillage operation, whereas the spring cohort was either prevented germinating by mechanical burial or chemically controlled upon germination during establishment of the summer crop. However, the absence of tillage operations allows survival of the autumn cohort, which turned out to be extremely difficult to control chemically in spring during seedbed preparation prior to sowing the summer crop, particularly when plants have grown large enough to tolerate commonly applied herbicide doses …”

“…However, the absence of tillage operations allows survival of the autumn cohort, which turned out to be extremely difficult to control chemically in spring during seedbed preparation prior to sowing the summer crop, particularly when plants have grown large enough to tolerate commonly applied herbicide doses. 21 A good example of plasticity in a dormancy strategy can be found in Polygonum aviculare (prostrate knotweed). Seeds from this summer annual weed are dispersed with high dormancy at the end of the summer and become buried easily due to their small size.…”

Dinámica de emergencia y competencia intraespecífica en Conyza sumatrensis

“…Trabajos realizados demuestran que la sensibilidad de rama negra a los tratamientos químicos es condicionada por el tamaño de las plantas, las dosis y el momento de aplicación (Nisensohn, Tuesca y Papa, 2011;Gianelli et al, 2015;Puricelli et al, 2015); por lo cual es necesario conocer los patrones de emergencia de esta maleza en cada región para determinar el momento oportuno de control.…”

“…A su vez, en Argentina se han desarrollado numerosos estudios que destacan la importancia de un control temprano de Conyza spp. en estadio de roseta y menor a 15 cm de altura durante el barbecho químico (Metzler, Puricelli y Papa, 2013;Ustarroz y Cerutti, 2015;Gianelli et al, 2015;Puricelli et al, 2015;Kahl 2016). En este sentido, la variación en tamaño y desarrollo de las plantas ocasionada por la competencia intraespecífica podría afectar la efectividad de las dosis de los tratamientos químicos utilizados para su control.…”