Sesame Tolerance to Preplant Applications of 2,4-D and Dicamba

Abstract

Two separate experiments were conducted in 2015 and 2016 in Citra, FL to investigate the effects of preplant application timing of 2,4-D and dicamba on sesame stand and yield. Nonlinear regression analysis was performed to determine the application timing that caused 10% stand or yield reduction (GR10) compared to the nontreated control (NTC) and expressed as d before planting (DBP; longer intervals indicate more injury). Likewise, regression analysis was used to determine sesame stand that resulted in 10% yield reduction (YR10) expressed as plants m−1row. Stand measured 3 wk after planting (WAP) revealed 2,4-D applied at 0.53 kg ae ha−1to be the least injurious treatment to sesame stand (GR10=6.4 DBP). Conversely, dicamba at 1.12 kg ha−1produced a GR10of 15.7 DBP for sesame stand at 3 WAP. 2,4-D applied at 0.53 and 1.06 kg ha−1and dicamba applied at 0.56 kg ha−1had the lowest GR10for yield of 2, 3.7, and 3 DBP, respectively. Dicamba applied at 1.12 kg ha−1proved to be the most injurious treatment to yield, which produced a GR10value of 10.3 DBP. To simulate possible stand losses associated with dicamba or 2,4-D and the subsequent effect on yield, a separate experiment was conducted in which sesame was thinned to various plant densities and yield was recorded to determine the relationship between plant stand and seed yield. The regression analysis of these data was then compared to that of the experiment treated with 2,4-D and dicamba to separate any physiological effects of the herbicides that would lead to yield reduction from yield effects due to stand loss only. Rate constants were compared and no statistical differences were detected between herbicide and non-herbicide treatments, suggesting that yield reductions that occur from preplant applications of 2,4-D and dicamba were purely due to stand reductions.

Simulated rainfall following the preplant application of 2,4-D and dicamba in soybean

“…The soil residue of dicamba has more severe detrimental effects on soybean than 2,4-D, what may be related to the slow dissipation of dicamba in the environment (Kah et al 2007), whereas the 2,4-D dissipation occurs easily via hydrolysis and oxidation in wet conditions (Cessna et al 2017). Similar observations have been made for soybean, cotton and sesame (Prostko et al 2003, Thompson et al 2007, Sperry et al 2017.…”

“…These results confirm the information about intervals between the herbicide application and soybean planting included on the labels of 2,4-D products (Adapar 2017b). Likewise, several reports in the literature document the minimal effects of 2,4-D applied at preplanting in susceptible crops (Prostko et al 2003, York et al 2004, Thompson et al 2007, Silva et al 2011, Oliveira et al 2015, Sperry et al 2017. In addition, the soybean dry matter accumulation was higher than in the untreated control ( Figure 2C), a fact that may be explained by the occurrence of hormesis (Silva et al 2019).…”

“…The preplant application of auxin herbicides requires a minimum interval before planting susceptible crops; however, if rainfall precedes planting, it is possible to reduce this interval (Prostko et al 2003, York et al 2004, Thompson et al 2007, Sperry et al 2017. Thus, high rainfall volumes after the preplant application of 2,4-D and dicamba in soybean could reduce the deleterious effects of these herbicides on the soybean emergence and initial development.…”

Selectivity of Herbicides Applied in Preemergence and Diuron in Postemergence for Sesame

“…Although there are some herbicide options for use in preemergence in the sesame crop, the greatest difficulty is related to the control of eudicot weed species and also of volunteer soybean in postemergence when the sesame is cultivated in succession to the soybean, because the molecules available on the market have not shown selectivity, causing considerable damage to plants (Grichar et al, 2001b;Grichar et al, 2011;Sperry et al, 2017). The alternative of using full-action herbicides in directed jet, in addition to not effectively controlling the weeds located in the sowing line, presents a risk of sesame intoxication (Grichar et al, 2014).…”