Effects of Herbicide Management Practices on the Weed Density and Richness in 2,4-D- Resistant Cropping Systems in Indiana

Commercialization of 2,4-D-resistant soybean varieties allows for postemergence (POST) applications of 2,4-D in soybean. With the increase in POST applications of 2,4-D in soybean, shifts in weed populations may occur. A long-term field trial was conducted over seven years in a corn-soybean rotation. Weed populations were subjected to four herbicide strategies with variable levels of 2,4-D reliance. The strategies used included: 1) diversified glyphosate strategy with six herbicide sites of action (SOA); 2) 2,4-D reliant strategy with three SOA; 3) diversified 2,4-D reliant strategy with seven SOA; and 4) fully diversified strategy with eight SOA. Soil residual herbicides were utilized for both corn and soybean years, except for the 2,4-D reliant strategy which only utilized a residual herbicide during the corn years. A 52% or greater reduction in weed densities for all herbicide strategies, except the 2,4-D reliant strategy, was observed by the end of the study. However, the density of weeds tolerant to 2,4-D, such as monocots, increased after three years of selection pressure, and more than doubled after five years of selection pressure in the 2,4-D reliant strategy. Additionally, in the 2,4-D reliant strategy with three SOA, species richness was 30% higher in the soil seedbank compared to herbicides strategies with six or more SOA. In order to delay weed shifts, diversified herbicide strategies with more than three SOA that include residual herbicides should be used in corn:soybean rotational systems that utilize 2,4-D-resistant soybean.

Herbicide Options to Manage Novel Turf-type Bahiagrass (Paspalum notatum)

Herbicide management information is lacking for recently developed turf-type bahiagrass germplasm. The objective of this study was to evaluate the herbicide tolerance of nine experimental bahiagrass genotypes compared to the industry standard ‘Argentine’. The experimental entries included Argentine and ‘Wilmington’ mutants, and wild-type breeding lines. Plants were grown under greenhouse conditions, and twelve herbicides were applied at 1 and 2 times labeled rates. Bentazon, bromoxynil, carfentrazone + 2,4-D + MCPP + dicamba, and carfentrazone were classified as safe. Fluroxypyr, halosulfuron, and triclopyr + clopyralid reduced growth >50% when applied at twice the label rate. Fenoxaprop, sulfentrazone + imazethapyr, and thiencarbazone + iodosulfuron + dicamba reduced growth and caused turfgrass injury above an acceptable threshold (≥20%). In general, the Argentine mutants showed greater herbicide injury compared to the Wilmington-mutants. Although metsulfuron exceeded the acceptable injury threshold and stopped growth in all the genotypes, Argentine and genotype WT6 were the least injured by this herbicide. The experimental genotype WT6 consistently showed the greatest herbicide tolerance. Except for one genotype (WT4), the experimental genotypes responded similarly or better than Argentine to the tested herbicides, except for metsulfuron.

Cover crop management in the maize-wheat offseason

This research studied a suitable cover crop considering biomass accumulation and nutrient cycling and its herbicide management to be adopted in the maize-wheat offseason as well as its influence on wheat yield. Experiment was laid out as a randomized block design in a factorial scheme with five cover crops (Fagopyrum esculentum, Crotalaria juncea, Pennisetum glaucum, Urochloa brizantha and Crotalaria spectabilis at 2017/18 growing season and at 2018/19, Fagopyrum esculentum and Crotalaria spectabilis were switched for Dolichos lablab) and two herbicide management (Desiccation 17 days before and at the wheat Sowing day) with four replications. Fallow was used as a control. Fagopyrum esculentum showed the fastest cycle and can be recommended for shorter offseason periods (50 days). Pennisetum glaucum showed the highest biomass yield at both years, standing out as the best option for offseason periods of 70 to 80 days. Tradeoff between the additional biomass produced by millet and brachiaria between herbicide desiccation periods does not cover the wheat grain yield reduction, suggesting that its herbicide management should be anticipated. On the other hand, Crotalarias showed a linear increase in biomass along the periods without wheat yield effects and its herbicide dissection at the wheat sowing day is recommended

Effect of Weeding and Herbicide Management on Fibre Yield and Yield Attributes of Tossa Jute

The experiment was conducted at Jute Agriculture Experimental Station (JAES), Manikganj and Jute Research Regional Station, Faridpur during 2019 to find out the effect of weeding and herbicide management on fibre yield and yield attributes of Tossa jute (Var. O-9897) cultivation. Two herbicide treatments, such as; W1 = Fenoxaprop-p-ethyl (Whip Super 9 EC) and W2 = Ethoxysulfuron (Sunrice ® 150WG) were tested. There were 14 treatments. T1- T6 treatments did not include hand weeding which was done 20 days after the herbicide spray [T1 = 100% recommended doses (RD) of both W1and W2 where W2 was sprayed one day after that of W1, T 2 = 50% dose both of W1and W2 where W2 was sprayed one day after that of W1, T3 = 100% dose of both W1 and W2 where both of the herbicide mixed together and sprayed on the same day, T4 = 50% dose of both W1 and W2 where mixture of both were sprayed on the same day, T5 = only 100% dose of W1, T6 = only 100% dose of W2]. The treatments T7 - T12 included one had weeding following the application of herbicides [T7 = 100% dose both of W1 and W2 where W2 was sprayed 1 day after that of W1, T8 = 50% dose both of W1 and W2 where W2 was sprayed 1 day after of W1, T9 = 100% dose both of W1 and W2 were mixed and sprayed together on the same day, T10 = 50% dose both of W1 and W2 mixed together and sprayed same day, T11 = only 100% dose of W1, T12 = only 100% dose of W2]. The treatments T13 and T14 did not include herbicide application [T13 = Two hand weeding (20-25 and 45-50 DAS) and T14 = control with no herbicide application]. The experiment was laid out in RCBD with three replications. Results revealed that Khudesama (Echinochloa colonum) and Angulighash (Digitaria sanguinalis), Khudesama and Mutha (Cyperus rotundus) were best controlled by herbicide application. T3 gave highest fibre yield of 1.89 tha-1 when W1 and W2 sprayed at the same day with 100% RD. In case of one weeding 20 days after spray fibre yield and stick yield were differed significantly as compared to those of control at Manikganj. Treatment T7 gave highest fibre yield (3.11 t ha-1) when W2 sprayed after 1 day of W1 with 100% RD. At Faridpur, T3 gave the highest fibre yield (2.68 t ha-1) when W1 and W2 sprayed at the same day with 100% RD. Incase of one weeding 20 days after spray, T7 gave highest fiber yield (2.79 t ha-1) when W2 was sprayed 1 day after that of W1 with 100% RD. Bangladesh Agron. J. 2020, 23(1): 101-106

Cover Crops Management in the Soybean-Wheat Offseason

More than 2 million hectare of soil at the soybean-wheat offseason remains on fallow in Brazil. Therefore, this research studied a suitable cover crop and its herbicide management to be adopted is this period as well as its influence on wheat yield at the 2017/18 and 2018/19 growing season. Experiment was laid out as a randomized block design in a factorial scheme composed of four cover crops (Fagopyrum esculentum, Crotalaria juncea, Pennisetum glaucum and Urochloa brizantha) and two herbicide management [Anticipated Desiccation (17 days before) and Desiccation at the wheat Sowing day] with four replications. Fallow without cover crops was used as a control. The tradeoff between the additional biomass produced by millet and brachiaria between herbicide desiccation periods does not pay the wheat grain yield reduction, suggesting that its herbicide management should be anticipated. In the other hand, C. juncea showed a linear increase in biomass along the periods without wheat yield effects and its herbicide dissection at the wheat sowing day appears to be the best management. F. esculentum showed the fastest development cycle and can be recommended for shorter offseason periods. P. glaucum showed rapid growth and the highest biomass yield at both years, standing out as the best option for offseason periods from 70 to 80 days, although, anticipated herbicide management before wheat sowing resulted in higher grain yield at the second year of study. Further studies should consider other cover crop benefits as weed suppression, physical and chemical soil traits improvements and erosion reduction.

Herbicide management in glyphosate and sulfonylurea-tolerant soybeans

ABSTRACT: There is little information on the efficacy and selectivity of sulfonylureas, isolated and in association with glyphosate, in glyphosate and sulfonylurea-tolerant soybeans. Thus, the present study aims to evaluate the efficacy of weed control and selectivity of sulfonylureas, isolated and in association with glyphosate, at post-emergence (V4) of RR2/STS soybean. The experiments were conducted in the in areas located in Piracicaba City, São Paulo State (SP), Brazil (experiment I) and Palotina City, Paraná State (PR), Brazil (experiment II). Treatments were composed of application of the herbicides sulfometuron, chlorimuron, halosulfuron, ethoxysulfuron and glyphosate, isolated and in association, in the BMX Garra RR2/STS cultivar. Experiment I was conducted focusing on the evaluation of the efficacy of weed control; whereas experiment II focused mainly on the evaluation of herbicide selectivity. The experimental design was the randomized complete block, with four replications. Crop injury, weed control, and variables related to agronomic performance were evaluated. Data were submitted to analysis of variance, and the means of the treatments were compared with the Tukey test. Sulfonylureas in association with glyphosate were effective in weed control and selective for the BMX Garra RR2/STS soybean cultivar. The sulfometuron + chlorimuron + glyphosate association presented phytotoxic potential for the BMX Garra RR2/STS cultivar.