Effect of osmotic potential and temperature on germination of kochia (\u3ci\u3eBassia scoparia\u3c/i\u3e) populations from the U.S. Great Plains

Development of integrated weed management strategies requires knowledge of weed emergence timing and patterns, which are regulated primarily by water and thermal requirements for seed germination. Laboratory experiments were conducted in fall 2017 to fall 2018 to quantify the effect of osmotic potential and temperature on germination of 44 kochia [Bassia scoparia (L.) A.J. Scott] populations under controlled conditions. Bassia scoparia populations were collected in fall 2016 from northern (near Huntley, MT, and Powell, WY) and southern (near Lingle, WY, and Scottsbluff, NE) regions of the U.S. Great Plains. Ten osmotic potentials from 0 to −2.1 MPa and eight constant temperatures from 4 to 26 C were evaluated. Response of B. scoparia populations to osmotic potential did not differ between the northern and southern regions. At an osmotic potential of 0 MPa, all B. scoparia populations had greater than 98% germination, and the time to achieve 50% germination (t50) was less than 1 d. At −1.6 MPa, 25% of seeds of all B. scoparia populations germinated. Osmotic potentials of −0.85 and −1.9 MPa reduced B. scoparia germination by 10% and 90%, respectively. Regardless of temperature regime, all populations exhibited greater than 88% germination. The germination rate was highest at temperatures between 15 to 26 C and did not differ between populations from northern versus southern regions. At this temperature range, all populations had a t50 of less than 1 d. However, at 4 C, B. scoparia populations from the northern region had a higher germination rate (5 h) and cumulative germination (7%) than populations from the southern region. Overall, these results indicate a wide range of optimum temperatures and osmotic potential requirements for B. scoparia germination

4-Hydroxyphenylpyruvate Dioxygenase (HPPD)-Inhibiting Herbicides: Past, Present, and Future

The 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicides are primarily used for weed control in corn, barley, oat, rice, sorghum, sugarcane, and wheat production fields in the United States. The objectives of this review were to summarize (1) the history of HPPD-inhibitor and their use in the United States, (2) HPPD-inhibitor resistant weeds, their mechanism of resistance, and management, (3) interaction of HPPD-inhibitor with other herbicides, and (4) the future of HPPD-inhibitor-resistant crops. As of 2022, three broadleaf weeds (Palmer amaranth, waterhemp, and wild radish) have evolved resistance to the HPPD-inhibitor. The predominance of metabolic resistance to HPPD-inhibitor was found in aforementioned three weed species. Management of HPPD-inhibitor-resistant weeds can be accomplished using alternate herbicides such as glyphosate, glufosinate, 2,4-D, or dicamba; however, metabolic resistance poses a serious challenge, as the weeds may be cross-resistant to other herbicide sites of action, leading to limited herbicide options. The HPPD-inhibitor is commonly applied with photosystem II (PS II)-inhibitor to increase efficacy and weed control spectrum. The synergism with HPPD-inhibitor arises from depletion of plastoquinones, which allows increased binding of PS II-inhibitor to the D1 protein. New HPPD-inhibitor from azole carboxamides class is in development and expected to be available in the near future. The HPPD-inhibitor-resistant crops have been developed through overexpression of a resistant bacterial HPPD enzyme in plants and the overexpression of transgenes for HPPD and a microbial gene that enhances the production of HPPD substrate. Isoxaflutole-resistant soybean is commercially available, and it is expected that soybean resistant to other HPPD-inhibitor such as mesotrione, stacked with resistance to other herbicides, will be available in the near future

Multi-tactic ecological strategies to manage Bassia scoparia and Amaranthus tuberculatus in the cropping systems of Great Plains and Midwestern U.S.

Kochia (Bassia scoparia [L.] A.J. Scott) and waterhemp (Amaranthus tuberculatus [Moq.] J.D. Sauer) are one of the most troublesome weeds in the cropping systems of Great Plains and Midwestern United States, respectively. A widespread occurrence of multiple herbicide-resistant (MHR) B. scoparia and A. tuberculatus populations across the region has seriously limited herbicide options to control these weed species. Therefore, there is an immediate need for ecologically based, multi-tactic strategies to manage these weeds. Laboratory and field experiments were conducted during 2017 to 2019 at the Montana State University Southern Agricultural Research Center, Huntley, MT: 1) to quantify moisture and thermal requirements for germination of B. scoparia and 2) to quantify the effect of winter wheat cover crop and irrigation on B. scoparia emergence patterns across the U.S. Great Plains. Forty-four B. scoparia accessions were collected from northern (Huntley, MT; Powell, WY) and southern (Lingle, WY; Scottsbluff, NE) regions of the Great Plains. Moisture requirements for germination of B. scoparia accessions did not differ between northern and southern regions. It required a water potential of -0.85 MPa and -1.9 MPa to reduce B. scoparia germination by 10 and 90%, respectively. The germination rate was highest at temperatures between 14 and 26 C for all accessions and did not differ among locations. Winter wheat cover crop and irrigation treatments did not influence B. scoparia emergence in the northern region. In the southern region, the winter wheat cover crop did not reduce cumulative emergence of B. scoparia. However, irrigation prompted earlier and faster emergence of B. scoparia. This indicates that in the southern region of the Great Plains, B. scoparia emergence can effectively be stimulated by one to two irrigations during early spring and then controlled with either tillage or non-selective herbicides before planting late-season crops. Field experiments were conducted during 2019 and 2020 at two sites (Iowa State University Curtiss Farm in Ames, IA and Bruner Farm in Boone, IA) to design multi-tactic strategies to manage A. tuberculatus in a corn-soybean rotation. Effect of three herbicide programs (HP) on A. tuberculatus seed inputs was tested in the 2019 corn. The effects of previous year’s seed inputs, cereal rye cover crop, and narrow-row soybean on A. tuberculatus density, biomass, and seed production were tested in the 2020 soybean. A weed seed destructor was used to prevent seed inputs by A. tuberculatus escapes at soybean harvest. In corn, an HP with two sites of action provided only 35% control of A. tuberculatus compared with ≥97% control by an HP with three sites of action. In soybean, no new seed inputs from the previous year’s corn crop reduced A. tuberculatus density and biomass by >30% compared with seed inputs from the previous year’s corn crop. Including a cereal rye cover crop or using a narrow-row soybean reduced A. tuberculatus density by at least 13% and biomass by 50%, compared with a no cover crop or a wide-row soybean. The weed seed destructor physically destroyed 90% of A. tuberculatus seeds at soybean harvest. A combination of all four-control tactics (spanned over two years) reduced A. tuberculatus seed inputs by 95% at the time of soybean harvest. These results indicate that diverse control tactics targeting A. tuberculatus at different life-cycle stages can successfully manage MHR populations

A Fiberoptic Study Of Stop Production In Maithili

A fiber optic study was made to investigate the temporal course and width of the glottis during the production of four types of Maithili stops in initial, medial and final positions. The results show that the voiced-voiceless distinction correlates with the adduction-abduction gesture of the larynx. The study also suggests that glottal width is the key factor for aspiration and that sounds which are produced by a combination of vibrating vocal cords and aspiration should, in fact, be called 'voiced aspirated' consonants

Multi-tactic ecological strategies to manage Bassia scoparia and Amaranthus tuberculatus in the cropping systems of Great Plains and Midwestern U.S.

Kochia (Bassia scoparia [L.] A.J. Scott) and waterhemp (Amaranthus tuberculatus [Moq.] J.D. Sauer) are one of the most troublesome weeds in the cropping systems of Great Plains and Midwestern United States, respectively. A widespread occurrence of multiple herbicide-resistant (MHR) B. scoparia and A. tuberculatus populations across the region has seriously limited herbicide options to control these weed species. Therefore, there is an immediate need for ecologically based, multi-tactic strategies to manage these weeds. Laboratory and field experiments were conducted during 2017 to 2019 at the Montana State University Southern Agricultural Research Center, Huntley, MT: 1) to quantify moisture and thermal requirements for germination of B. scoparia and 2) to quantify the effect of winter wheat cover crop and irrigation on B. scoparia emergence patterns across the U.S. Great Plains. Forty-four B. scoparia accessions were collected from northern (Huntley, MT; Powell, WY) and southern (Lingle, WY; Scottsbluff, NE) regions of the Great Plains. Moisture requirements for germination of B. scoparia accessions did not differ between northern and southern regions. It required a water potential of -0.85 MPa and -1.9 MPa to reduce B. scoparia germination by 10 and 90%, respectively. The germination rate was highest at temperatures between 14 and 26 C for all accessions and did not differ among locations. Winter wheat cover crop and irrigation treatments did not influence B. scoparia emergence in the northern region. In the southern region, the winter wheat cover crop did not reduce cumulative emergence of B. scoparia. However, irrigation prompted earlier and faster emergence of B. scoparia. This indicates that in the southern region of the Great Plains, B. scoparia emergence can effectively be stimulated by one to two irrigations during early spring and then controlled with either tillage or non-selective herbicides before planting late-season crops. Field experiments were conducted during 2019 and 2020 at two sites (Iowa State University Curtiss Farm in Ames, IA and Bruner Farm in Boone, IA) to design multi-tactic strategies to manage A. tuberculatus in a corn-soybean rotation. Effect of three herbicide programs (HP) on A. tuberculatus seed inputs was tested in the 2019 corn. The effects of previous year’s seed inputs, cereal rye cover crop, and narrow-row soybean on A. tuberculatus density, biomass, and seed production were tested in the 2020 soybean. A weed seed destructor was used to prevent seed inputs by A. tuberculatus escapes at soybean harvest. In corn, an HP with two sites of action provided only 35% control of A. tuberculatus compared with ≥97% control by an HP with three sites of action. In soybean, no new seed inputs from the previous year’s corn crop reduced A. tuberculatus density and biomass by >30% compared with seed inputs from the previous year’s corn crop. Including a cereal rye cover crop or using a narrow-row soybean reduced A. tuberculatus density by at least 13% and biomass by 50%, compared with a no cover crop or a wide-row soybean. The weed seed destructor physically destroyed 90% of A. tuberculatus seeds at soybean harvest. A combination of all four-control tactics (spanned over two years) reduced A. tuberculatus seed inputs by 95% at the time of soybean harvest. These results indicate that diverse control tactics targeting A. tuberculatus at different life-cycle stages can successfully manage MHR populations

A Fiberoptic Study Of Stop Production In Maithili

A fiber optic study was made to investigate the temporal course and width of the glottis during the production of four types of Maithili stops in initial, medial and final positions. The results show that the voiced-voiceless distinction correlates with the adduction-abduction gesture of the larynx. The study also suggests that glottal width is the key factor for aspiration and that sounds which are produced by a combination of vibrating vocal cords and aspiration should, in fact, be called 'voiced aspirated' consonants

Multi-tactic ecological strategies to manage Bassia scoparia and Amaranthus tuberculatus in the cropping systems of Great Plains and Midwestern U.S.

Kochia (Bassia scoparia [L.] A.J. Scott) and waterhemp (Amaranthus tuberculatus [Moq.] J.D. Sauer) are one of the most troublesome weeds in the cropping systems of Great Plains and Midwestern United States, respectively. A widespread occurrence of multiple herbicide-resistant (MHR) B. scoparia and A. tuberculatus populations across the region has seriously limited herbicide options to control these weed species. Therefore, there is an immediate need for ecologically based, multi-tactic strategies to manage these weeds. Laboratory and field experiments were conducted during 2017 to 2019 at the Montana State University Southern Agricultural Research Center, Huntley, MT: 1) to quantify moisture and thermal requirements for germination of B. scoparia and 2) to quantify the effect of winter wheat cover crop and irrigation on B. scoparia emergence patterns across the U.S. Great Plains. Forty-four B. scoparia accessions were collected from northern (Huntley, MT; Powell, WY) and southern (Lingle, WY; Scottsbluff, NE) regions of the Great Plains. Moisture requirements for germination of B. scoparia accessions did not differ between northern and southern regions. It required a water potential of -0.85 MPa and -1.9 MPa to reduce B. scoparia germination by 10 and 90%, respectively. The germination rate was highest at temperatures between 14 and 26 C for all accessions and did not differ among locations. Winter wheat cover crop and irrigation treatments did not influence B. scoparia emergence in the northern region. In the southern region, the winter wheat cover crop did not reduce cumulative emergence of B. scoparia. However, irrigation prompted earlier and faster emergence of B. scoparia. This indicates that in the southern region of the Great Plains, B. scoparia emergence can effectively be stimulated by one to two irrigations during early spring and then controlled with either tillage or non-selective herbicides before planting late-season crops. Field experiments were conducted during 2019 and 2020 at two sites (Iowa State University Curtiss Farm in Ames, IA and Bruner Farm in Boone, IA) to design multi-tactic strategies to manage A. tuberculatus in a corn-soybean rotation. Effect of three herbicide programs (HP) on A. tuberculatus seed inputs was tested in the 2019 corn. The effects of previous year’s seed inputs, cereal rye cover crop, and narrow-row soybean on A. tuberculatus density, biomass, and seed production were tested in the 2020 soybean. A weed seed destructor was used to prevent seed inputs by A. tuberculatus escapes at soybean harvest. In corn, an HP with two sites of action provided only 35% control of A. tuberculatus compared with ≥97% control by an HP with three sites of action. In soybean, no new seed inputs from the previous year’s corn crop reduced A. tuberculatus density and biomass by >30% compared with seed inputs from the previous year’s corn crop. Including a cereal rye cover crop or using a narrow-row soybean reduced A. tuberculatus density by at least 13% and biomass by 50%, compared with a no cover crop or a wide-row soybean. The weed seed destructor physically destroyed 90% of A. tuberculatus seeds at soybean harvest. A combination of all four-control tactics (spanned over two years) reduced A. tuberculatus seed inputs by 95% at the time of soybean harvest. These results indicate that diverse control tactics targeting A. tuberculatus at different life-cycle stages can successfully manage MHR populations