Selectivity index of indaziflam to sugarcane cv. IACSP95-5000 in two soil textures

Abstract

Selectivity index is a way of assessing the discrimination of herbicide to a given crop by observing its effects on the crop and the weeds. The aim was to obtain the selectivity index of indaziflam herbicide to sugarcane cultivar IACSP95-5000 as a function of five weed species in two soils textures. The experiment was carried out in a greenhouse at Piracicaba, São Paulo, Brazil. The treatments consisted of indaziflam doses (0; 12.5; 25; 50; 100; 200; 400; 800 and 1,600 g of the active ingredient (ai) ha-1), applied in pre-emergence of the sugarcane and of the weeds Urochloa decumbens, Urochloa plantaginea, Digitaria horizontalis, Panicum maximum and Rottboellia cochinchinensis. In sandy loam soil, a 100% control for all weeds was provided at 25 g ai ha-1. In clay soil, for D. horizontalis the 90% reduction in total dry mass (ED90) was obtained at 25 g ai ha-1, for R. cochinchinensis at 193 g ai ha-1, for U. plantaginea at 152 g ai ha-1, for P. maximum at 124 g ai ha-1, and for U. decumbens at 94 g ai ha-1. Indaziflam was selective to IACSP95-5000 in both soils, with 10% of reduction in dry mass (ED10) at 137 g ai ha-1 for soil with a sandy loam texture and 353 g ai ha-1 for clay soil. The selectivity index was higher than 1 for all weeds in clay soil. It was not possible to obtain the selectivity index for sandy loam soil due to species susceptibility to the herbicide.

Managing itchgrass and morningglory in plant cane: a strong decision on associating herbicides for pre-emergence control

“…Overall, when applying the herbicide, there was a reduction of 9.3 mm per day in itchgrass growth. Herbicide usage is the most commonly used method for weed management in sugarcane cultivation, especially when positioned in pre-emergence conditions, as it ensures a prolonged residual effect and control effectiveness during the critical period of competition with the crop (Ghirardello et al 2021;Presoto et al 2022), as con rmed by the present study.…”

“…One herbicide molecule that may provide a long weed control period against itchgrass and/or morningglory, independent of the rainfall accumulated, is indazi am, as occurred in our study (Table 2). Ghirardello et al (2021) found that indazi am (100 g i.a ha − 1 ) provides a long period of controlling weeds of the family Poaceae, including R. exaltata, especially in soils of a more clayey texture, as in our situation. Rodrigues et al (2022) stated that R. exaltata was controlled by the herbicide indazi am at dosages of 75, 150, and 225 mL in pre-emergence, as the control percentages remained high (above 91%) after 84 DAA compared with the control treatment, a fact that expresses the long residual effect of indazi am (Rodrigues et al 2022).…”

“…Selectivity is the ability of the herbicide to control weeds without impairing the quality of sugarcane (Sousa et al 2020). This possible damage to some sugarcane varieties is associated with such characteristics of plants as differential absorption and translocation, their age, cultivar, differential metabolism, dimensions of seeds or propagation structures, and factors related to the characteristics of herbicides and their application modes, such as dose, formulation, and selectivity by position (Araldi et al 2011;Ghirardello et al 2021). According to the literature, when indazi am was applied in isolation, it was selective for the IACSP95-5000 sugarcane cultivar (Ghirardello et al 2021).…”

“…This possible damage to some sugarcane varieties is associated with such characteristics of plants as differential absorption and translocation, their age, cultivar, differential metabolism, dimensions of seeds or propagation structures, and factors related to the characteristics of herbicides and their application modes, such as dose, formulation, and selectivity by position (Araldi et al 2011;Ghirardello et al 2021). According to the literature, when indazi am was applied in isolation, it was selective for the IACSP95-5000 sugarcane cultivar (Ghirardello et al 2021). Maintaining high doses of indazi am application (300 g ai ha -1 ) did not cause injury to the sugarcane (RB867515 cultivar) in an area with sandy soil (Simões 2018).…”

“…Therefore, the weed interference is very critical in planting cane because of the weed community, the crop itself, the time and the duration of the co-existence period between the crop and the weed (Kuva et al 2000;Freitas et al 2004). For weed management in sugarcane, the most used method is herbicide application under pre-emergence conditions, as it ensures a prolonged residual effect and control effectiveness during the critical period of competition with the sugarcane crop (Mascarenhas et al 1995;Carbonari et al 2010;Toledo et al 2015;Ghirardello et al 2021;Presoto et al 2022). Another aspect that is crucial to know the composition of the weed community present in the eld, given that this information would enable decision-making about the herbicide molecule to apply on the eld after the planting.…”