Abstract
In the State of Rio Grande do Sul (RS), Southern Brazil, glyphosate has not been capable of controlling wild poinsettia (Euphorbia heterophylla L.) in soybean fields, thus, suggesting resistance to this herbicide. Therefore, this study aimed at evaluating sensitivity of wild poinsettia biotypes to glyphosate, identifying the occurrence of resistance of wild poinsettia to the herbicide in RS state and determining the resistance factor of wild poinsettia biotypes under suspicion, besides assessing other herbicides as alternative controls. Two greenhouse experiments, which lasted two years, were conducted by a completely randomized design with four replications. Six biotypes (Factor A) and eight doses of glyphosate (Factor B) were used for getting the dose-response curve. Regarding the alternative control, post-emergence herbicides for soybean and corn crops were tested. Control and dry mass of the shoot were analyzed as variables. Resistance factors of resistant biotypes 20.2 and 21.1 were 4.83 and 5.29, respectively, by comparison with the susceptible biotype (11.4). In RS state, there has currently been high selection pressure due to the intensive use of glyphosate against wild poinsettia plants, as the result of the occurrence of biotypes 20.2 and 21.1 which have low levels of resistance to glyphosate and very little control by ALS-inhibiting herbicides. Therefore, an alternative to mitigate the problem is the use of herbicides with different mechanisms of action.
Highlights
Wild poinsettia (Euphorbia heterophylla L.) is a weed Euphorbiaceae which has been known as one of the most important infestant of soybean crops (TREZZI et al, 2006; RIZZARDI; SILVA, 2014)
Differences in weed susceptibility to glyphosate were reported in Chloris polydactyla (L.) Sw., i. e., groups of biotypes with high tolerance, intermediate tolerance and susceptibility to the herbicide were classified (BARROSO et al, 2014)
There are wild poinsettia biotypes, from Condor (21.1) and Pontão (20.2), with low-level resistance to the glyphosate. The control of this biotypes by ALSinhibiting herbicides is smaller, but they are controlled by herbicides atrazine, glufosinateammonium and 2,4-D, which have different mechanisms of action
Summary
Wild poinsettia (Euphorbia heterophylla L.) is a weed Euphorbiaceae which has been known as one of the most important infestant of soybean crops (TREZZI et al, 2006; RIZZARDI; SILVA, 2014). In order to mitigate productivity loss, weed control has been almost exclusively carried out by herbicides because of their efficiency and high benefit-cost ratio. Resistance has been defined as the inherent and inheritable capacity a biotype has, in a certain population, to survive and reproduce after exposure to the registered herbicide dose, which is usually lethal to the susceptible population of the same species (GAZZIERO et al, 2014). There are differences in the control of biotypes of certain weeds in cases in which doses are below the ones recommended by the information booklet. In these cases, scientific resistance, known as low level of resistance, can be considered. In Brazil, wild poinsettia has been reported as being resistant to herbicides which inhibit acetolactate synthase (ALS) (VIDAL; MEROTTO JÚNIOR, 1999) and protoporphyrinogen oxidase (PROTOX) (TREZZI et al, 2005)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
