Selecting glyphosate-resistant Digitaria insularis may cause changes in the biological cycle of the species. Therefore, the objective of this study was to evaluate the biological cycle of susceptible and glyphosate-resistant D. insularis biotypes in two growth periods (summer/autumn and autumn/winter). Seeds were collected in the municipality of Alagoa Grande (07o02’59" S 35o37’01,5" W), and were considered susceptible (S1), in Cascavel (24o55’27" S 53o27’54.6 ”W) considered as resistant 1 (R1), Entre Rios do Oeste (24o40’44" S 54o17’05" W) considered as resistant 2 (R2) and Marechal Cândido Rondon (24o42’30" S 54o21’10" W) considered as resistant 3 (R3). Evaluations were carried out in the summer/autumn and autumn/winter periods. The collection periods of plants were: 14; 21; 28; 35; 42; 49; 56; 63; 70; 77; 84; 91; 98; 105; 112 and 119 days after emergence (DAE). The selection of glyphosate-resistant D. insularis biotypes in agricultural areas affected the biology of the species, in relation to the original population of the susceptible biotype. In the summer/autumn period (mean temperature 24.6 oC), the S biotype started the emission of tillers and flowering at 14 and 21 DAE on an average, respectively, before the resistant biotypes. However, in the autumn/winter period (mean temperature 19.0 oC) only the R1 biotype was able to develop and complete the biological cycle. The evaluated biotypes presented differences during the development, mainly between the phenological stages, so that the susceptible biotype was the most precocious and with a high reproductive potential. The physiological evaluations showed no differences among the S, R1, R2 and R3 biotypes, as verified in the TCR.
A new cycle of growth begins after pruning of cassava, and weed control is necessary. Thus, this study aimed to evaluate the selectivity and efficiency of sequential application of herbicides alone and in mixture with and without of foliar fertilizer after pruning of cassava. Two experiments were carried out in a randomized block design with four replications. The treatments of Experiment 1 consisted of control without weeding; control with weeding; mesotrione; mesotrione/mesotrione; mesotrione + foliar fertilizer/mesotrione + foliar fertilizer; mesotrione/mesotrione + foliar fertilizer; mesotrione + clethodim; mesotrione + clethodim + foliar fertilizer/mesotrione + clethodim + foliar fertilizer; mesotrione + clethodim/mesotrione + clethodim; mesotrione + clethodim/chlorimuron; mesotrione + clethodim/chlorimuron + foliar fertilizer; mesotrione + clethodim + foliar fertilizer/chlorimuron + clethodim + foliar fertilizer; mesotrione + clethodim/chlorimuron + clethodim]. Treatments of Experiment 2 consisted of control without weeding; control with weeding; chlorimuron; chlorimuron + foliar fertilizer/chlorimuron + foliar fertilizer; chlorimuron/chlorimuron; chlorimuron + clethodim; chlorimuron + clethodim + foliar fertilizer/chlorimuron + clethodim + foliar fertilizer; chlorimuron + clethodim/chlorimuron + clethodim; chlorimuron + clethodim/mesotrione + foliar fertilizer; chlorimuron + clethodim/mesotrione; chlorimuron + clethodim + foliar fertilizer/mesotrione + clethodim + foliar fertilizer; chlorimuron + clethodim/mesotrione + clethodim. The doses of mesotrione, clethodim, and chlorimuron used in both experiments were 240, 120, and 20 g ha-1, respectively, while 2.5 L of the commercial product Amino Plus® was used as foliar fertilizer. The first application was carried out at 50 days after pruning and the second application at 22 days after the first application. In Experiment 1, the application of mesotrione, mesotrione/mesotrione, and mesotrione + clethodim/mesotrione + clethodim showed selectivity to cassava and were efficient in weed control. In Experiment 2, chlorimuron + clethodim/mesotrione, chlorimuron + clethodim + foliar fertilizer/mesotrione + clethodim + foliar fertilizer, and chlorimuron + clethodim/mesotrione + clethodim were efficient in weed control, but no treatment was selective. The addition of foliar fertilizer to the spray solution did not contribute to increase selectivity.
The use of strategies such as sequential applications and mixtures may increase the control spectrum and the residual effect of chemical control of weed in the cassava crop. Thus, the objective was to evaluate the selectivity and efficacy of sequential applications and tank mixture of herbicides in the control of weed in the cassava crop cultivar 'Baianinha'. The experimental design was of randomized blocks, with eleven treatments and four replicates. The treatments consisted in: harrowed control, control without harrow, clomazone, mesotrione, S-metolachlor, clomazone+S-metolachlor, mesotrione+S-metolachlor, clomazone+mesotrione, sulfentrazone/clomazone, clomazone/[mesotrione+S-metolachlor], S-metolachlor/[mesotrione+clomazone]. The doses used for clomazone, mesotrione, sulfentrazone and S-metolachlor in the single applications, in sequence and in tank mixture were of 1.25, 0.24; 0.6 and 1.92 kg ha -1 , respectively. The first application of the sequential treatments occurred 50 days after planting (DAP) and the second at 92 DAP. The applications of mesotrione, mesotrione+clomazone and mesotrione+S-metolachlor, were carried late, at 92 DAP. Based on the data obtained, it is concluded that the mixture mesotrione+S-metolachlor and the sequential application of clomazone/ [mesotrione+S-metolachlor] were selective to cassava 'Baianinha' and efficient in the weed control (over 80% up to 148 days after planting).
The objective of the present study was to evaluate the row hoe model CHOPSTAR®, the mechanical control of weeds in between the rows of soybean implanted in organic direct sowing system, associated with the camera-guided system. Two experiments were carried, being that in the first experiment an experimental design with sub-subdivided plots with four replicates. The plots corresponded to two soybean varieties ('Embrapa BRS 284' and 'Coodetec CD 216'), the subplots corresponded to the sowing densities of 329.2 and 574.6 thousand plants ha -1 ; and the subsubplots corresponded to four managements of weeds: one mechanized hoe (2 days after sowing -DAS), two mechanized hoes (22 and 47 DAS), one control manually hoed and other control without hoeing. In the second experiment a randomized block design in subdivided plots with three replicates was used. The plots corresponded to two soybean varieties ('BRS 284' and 'DF 2353'), Fey et al.; JEAI, 42(2): 25-36, 2020; Article no.JEAI.55215 26 the subplots constituted of different times when the hoes were made, being: one (14 DAS); two (7 and 21 DAS; two (14 and 28 DAS); three (7, 14 and 28 DAS); besides one control manually hoed up to 28 DAS. In the first experiment it was observed that the automatized hoe was efficient in controlling the weeds and it was necessary only one mechanized hoe (22 DAS) for the 'BRS 284' independent of the sowing density, while for the 'CD 216' the number of mechanized hoes depended on the sowing density. In the second experiment, it was necessary only one mechanized hoe (14 DAS) to avoid production losses in the varieties 'BRS 284' and 'DF 2353'. The automatized hoe is an alternative to control weeds in areas of organic soybean in direct sowing system, however, damages to the crop can occur depending on the sowing density, mainly in the late management of the mechanized hoe. Original Research Article
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