Digitaria Ciliaris Research Articles

Registration of ‘Impact’ Crabgrass

Impact (Reg. No. CV‐283, PI 687328) crabgrass [Digitaria ciliaris (Retz.) Koeler] was developed by the Noble Research Institute, LLC, and released in 2016. Selections were made from ‘Red River’ by recurrent phenotypic selection for late flowering and high individual plant yield. In Ardmore, OK, trials in 2014 and 2015, Impact headed significantly later than Red River and the early‐maturing cultivar Quick‐n‐Big. This later maturity produced in vitro true dry matter digestibility numerically greater than Red River and significantly greater than Quick‐n‐Big (697 g kg−1 vs. 685 and 665 g kg−1, respectively, across 11 harvests) and lower neutral detergent fiber (635 g kg−1 vs. 654 g kg−1) than Quick‐n‐Big. In Oklahoma, there were no consistent differences in monthly or total dry matter yields in Impact compared with Red River (Impact ranged from 9160 to 19,764 kg ha−1, depending on year and location), but Impact yielded higher during most late‐season harvest dates (mid‐August–early October) compared with Quick‐n‐Big. At Vashti, TX, during 2014, Impact produced more monthly forage and total dry matter yield than both Red River and Quick‐n‐Big. In Mississippi and Tennessee, cultivar differences were similar to Oklahoma results. Impact demonstrated summer animal gains of 0.78 kg d−1 and total season gains of 230 kg ha−1. It is high yielding and should be broadly adapted as annual summer pasture throughout the south‐central and southeastern United States.

Interference Periods of Weeds Infesting Maize Crop

When competing with crops, weeds interfere with their growth and consequently reduce grain yield. The purpose of this research was to determine the periods of interference; PIP (pre-interference period), TPWC (total period of weed control), and CPWC (critical period of weed control) of the weeds Alexandergrass (Urochloa plantaginea) and southern crabgrass (Digitaria ciliares) in maize. The experiment was conducted in a randomized complete block design with four replications, in a no-tillage system. The treatments consisted in maintaining maize in the presence and absence of Alexandergrass and southern crabgrass for increasing periods of 0, 7, 14, 21, 28, 35 and 42 days after emergence (DAE). Southern crabgrass and Alexandergrass weeds originated from the soil seed bank with an average density of 215 and 87 plants m-2, respectively. At the end of each period, PIP or TPWC, the weed and crop dry biomass was determined. At 42 DAE, the height and stem diameter of maize plants were evaluated. At harvest 10 maize plants per experimental unit were evaluated for length of ears, number of rows per ear, and number of grains per row. Yield was measured by taking three central rows from each experimental unit. The results indicate that the PIP was 17 DAE, the TPWC was 32 DAE, and the CPWC was 17 to 32 DAE.

Manejo de plantas daninhas em milho RR® com herbicidas aplicados isoladamente ou associados ao glyphosate

The objective of this work was to evaluate the effectiveness, selectivity and effect on yield components of RR® maize as a function of herbicide application, applied alone or in a tank mix. The experiment was conducted in a randomized block design, with four replications, and treatments were control without weeding, control with weeding, glyphosate, glyphosate + [atrazine+simazine], glyphosate + [atrazine + simazine], glyphosate + tembotrione, glyphosate+mesotrione, T8-glyphosate + nicosulfuron, glyphosate + 2,4-D, glyphosate + [atrazine + S-metolachlor], T11-glyphosate + (atrazine + S-metolachlor), glyphosate + S-metolachlor, glufosinate ammonium, [nicosulfuron + mesotrione], glyphosate + [nicosulfuron + mesotrione] and glyphosate + [nicosulfuron+mesotrione] + [atrazine + simazine]. Herbicide phytotoxicity to a SYN Supremo VIP3 maize hybrid and control of Urochloa plantaginea and Digitaria ciliaris were evaluated at 7, 14, 21 and 28 days after treatment application. Prior to crop harvest, we determined weed control and, in ten plants per experimental unit, the variables related to grain yield components such as ear insertion height, ear length, number of rows and grains per rows on the ears of corn. During harvest, the mass of one thousand grains and yield were evaluated. It was observed that all herbicide treatments caused low phytotoxicity in maize, except for the post-emergence tank mix composed of glyphosate + 2,4-D and glyphosate + mesotrione, that showed the highest injuries in the four evaluated periods. Most of the herbicides showed good control of D. ciliaris and U. plantaginea, except for the pre-harvest mixture of glyphosate + 2,4-D. The post-emergence glyphosate + [atrazine + simazine] tank mix demonstrated the highest grain yield. It can be concluded, therefore, that depending on the association of herbicides, synergistic effect occurs for both weed control and crop phytotoxicity, being productivity being the main influenced variable.

Weed Management in Beans Using Subdoses of Fluazifop-P-Butyl + Fomesafen

ABSTRACT: The objective of this work was to evaluate the effect of reduced doses of the commercial mixture composed of fluazifop-p-butil + fomesafen, applied for the management of common weeds in beans. The experiment was conducted in a completely randomized block design, with a 5x2+1 factorial arrangement and with four replications. In factor A, there were five percentual doses (100, 87.5, 75.0, 62.5 and 0.0%), in relation to the recommended commercial dose (2 L ha-1) of fluazifop-p-butil + fomesafen, which corresponded to 2.00; 1.75; 1.50; 1.25 and 0.00 L ha-1. Factor B was composed by two development stages of black beans (three and eight trefoils) and weeds: black-jack (two to four and four to eight leaves) and southern crabgrass (two leaves to one tiller and one to four tillers) with one weeded control treatment. The variables evaluated for the control of black-jack and southern crabgrass were: herbicide phytotoxicity to the crop, number of pods per plant, number of grains per pod, 1,000 grain weight and grain yield of the crop. The results demonstrated that the use of fluazifop-p-butil + fomesafen, at all evaluated doses evaluated and application periods, caused low phytotoxicity to the crop, less than 12%. The use of reduced doses of this herbicide presents efficient control of black-jack and southern crabgrass, mainly at the initial development stages of these weed species. The economic threshold dosage of fluazifop-p-butil + fomesafen to control these weeds was 1.23 L ha-1.

Eficácia de herbicidas inibidores da síntese de carotenoides no controle de espécies de capim-colchão

The sugarcane sector currently is difficulties in the weed management in areas with occurrence of crabgrass (Digitaria spp.) is very high. The objective of this study was to evaluate the efficacy of herbicides inhibitors of synthesis of carotenoids in three species of Digitaria horizontalis, Digitaria ciliaris, Digitaria nuda. The experiment was conducted in greenhouse in a completely randomized design with four replications. Dose-response biossays for each species were performed with increasing doses of isoxaflutole (112.5 g i.a. ha-1) and clomazone (1200 g i.a. ha-1) applied in pre-emergence, represented by 0; 12.5; 25; 50 and 100% of the dose recommended (N) for use in sugarcane cultivation. The efficacy of the treatments on the different crabgrass species was verified through the evaluation of the visual control score performed at 14, 21 and 30 days after application (DAA) and shoot dry mass (SDM) at 30 DAA. The herbicides isoxaflutole and clomazone provided high levels of fitointoxication and reduction in SDM, demonstrating the efficacy of these herbicides for the crabgrass plants. There was a difference in sensitivity in the lower doses of herbicides used as a function of each species.

Responses of Ten Weed Species to Microwave Radiation Exposure as Affected by Plant Size1

Abstract There is interest in alternative weed control methods to herbicide use, especially among those interested in organic approaches. The use of microwave radiation as a weed control method appears to be a good alternative because it does not produce chemical residues in the environment. A study was conducted to determine the impact of plant age on weed control using microwave radiation. Ten weed species, representing monocots and dicots, were selected for this study: southern crabgrass (Digitaria ciliaris (Retz.) Koeler), dallisgrass (Paspalum dilatatum Poir.), false green kyllinga (Kyllinga gracillima Miquel), fragrant flatsedge (Cyperus odoratus L.), yellow nutsedge (Cyperus esculentus L.) common ragweed (Ambrosia artemisiifolia L.), white clover (Trifolium repens L.), pitted morningglory (Ipomoea lacunosa L.), henbit (Lamium amplexicaule L.) and field bindweed (Convolvulus arvensis L.). In general, weed species become more tolerant of microwave treatments as they increased in size, as 8 to 10 week-old plants were injured less than 4 to 6 week-old plants. Most grass species regrew when treated at 90 and 180 joules.cm−2 of microwave radiation. Pitted morningglory and common ragweed showed the highest susceptibility to microwave radiation among all treated weed species. The increase in a weed's biomass over time probably increases the amount of microwave radiation necessary for heating samples to the thermal threshold required for control. Index words: Nonchemical control, microwave, weed age, weed maturity, thermal weed control. Species used in this study: southern crabgrass (Digitaria ciliaris (Retz.) Koeler); dallisgrass (Paspalum dilatatum Poir.); false green kyllinga (Kyllinga gracillima Miquel); fragrant flatsedge (Cyperus odoratus L.); yellow nutsedge (Cyperus esculentus L.); common ragweed (Ambrosia artemisiifolia L.); white clover (Trifolium repens L.); pitted morningglory (Ipomoea lacunosa L.); henbit (Lamium amplexicaule L.); field bindweed (Convolvulus arvensis L.).

Weed Management in Common Cottonwood (Populus deltoides) Nursery Plantation

AbstractCommon cottonwood-based agroforestry system is widely adopted in Indian Indo-Gangetic plains. The stem cuttings of common cottonwood are raised in a nursery 10 to 12 months in rows spaced 0.5 mx0.5 m, before re-planting in the field. The longer duration of 10 to 12 months and wider spacing of stem cuttings in the nursery makes the entire transplants highly vulnerable to weed competition, especially during early establishment stages. The efficacy of preemergence herbicides and plastic and straw mulches for weed management in common cottonwood nursery was investigated at two sites in years 2014 and 2015. The major weed flora in the experimental field consisted of three grass weeds (crowfootgrass, feather lovegrass, and southern crabgrass), and four broadleaf weeds (scarlet pimpernel, garden spurge, niruri, and lesser swinecress). The integrated use of pendimethalin or alachlor applied PRE with paddy straw mulch significantly reduced density and biomass of both grass and broadleaf weeds compared to herbicide or straw mulch used alone, and provided similar level of weed control to hand weeding at both locations. Spreading of plastic mulch in the whole field after punching holes for common cottonwood stem cuttings, or in row spaces recorded similar weed control to hand-weeding. The integrated use of herbicides with straw mulch, and or plastic mulch alone significantly improved plant height, stem diameter, below- and above-ground biomass of common cottonwood plants compared to unweeded check. The study concluded that integrated use of herbicides plus paddy straw mulch or plastic mulch alone could be adopted for weed management in common cottonwood nursery plantations.

Herbicidal and Seed Dormancy Induction Activity of Fermentation Residual Vinasse

AbstractVinasse, a liquid fermentation residual of bio-ethanol production that also contains solid particles in suspension, is commonly used as a soil amendment. Previous studies reported vinasse reduced seed germination and seedling establishment, suggesting herbicidal activity. Laboratory experiments were conducted to determine whether vinasse herbicidal activity is present in the liquid or solid phase, and whether it affects plants during seed early germination (i.e., imbibition), late germination (i.e., embryo growth and radicle protrusion), or seedling growth. Most of the herbicidal activity was associated with the liquid phase, and for most species, seed viability was predominantly affected after the imbibition phase. Susceptibility to vinasse was species dependent. Lettuce (Lactuca sativaL.) germination was <8% when seeds were imbibed and germinated in vinasse solutions or imbibed in water and germinated in vinasse. Conversely, imbibing lettuce seeds in vinasse solutions and germinating them in water did not change their germination in comparison with seeds imbibed and germinated in water (>80% germination). Wheat (Triticum aestivumL.) and sicklepod [Senna obtusifolia(L.) H. S. Irwin & Barneby] germination decreased 10% and 35% when seeds were imbibed and germinated in vinasse, respectively, while Palmer amaranth (Amaranthus palmeriS. Watson) and southern crabgrass [Digitaria ciliaris(Retz.) Koeler] germination decreased >90%. All evaluated species reduced radicle growth as vinasse concentration increased. Filtered liquid vinasse with reduced concentration of salt and ionic compounds inhibited radicle growth similarly to unfiltered vinasse, indicating that the herbicidal activity was not due to osmotic effects and was likely present in the organic liquid phase.Amaranthus palmeri,S. obtusifolia, andD. ciliarisincreased the proportion of dormant seed more than 2-fold when they were imbibed or imbibed and germinated in vinasse solutions. Vinasse might be useful for weed management to reduce germinable weed seedbanks by increasing seedling mortality and seed dormancy either by properly timing of its application as a soil amendment or by purifying herbicidal compounds and using them directly for weed control.

Associação de herbicidas para o controle de plantas daninhas em feijão do tipo preto

O feijão do tipo preto é um dos principais grãos cultivados no Brasil, com importância econômica, social e cultural. As perdas de produtividade de grãos, por competição com as plantas daninhas, em especial Digitaria ciliaris (milhã/capim-colchão) e Urochloa plantaginea (capim marmelada/papuã) podem chegar a níveis de até 80% caso nem um método de controle for adotado. Buscando o controle dessas plantas daninhas, objetivou-se com o trabalho avaliar a eficácia e a seletividade de herbicidas aplicados em pré e pós-emergência do feijão do tipo preto. O delineamento experimental utilizado foi de blocos casualizados, com quatro repetições. Os herbicidas utilizados foram: fomesafen (250 g ha-1 de i.a), s-metolachlor (1200 g ha-1 de i.a), oxifluorfen (480 g ha-1 de i.a), clomazone (1000 g ha-1 de i.a), pendimentalin (1000 g ha-1 de i.a), flumioxazin (25 g ha-1 de i.a), fluazifop-p-buthyl (250 g ha-1 de i.a), imazamox (42 g ha-1 de i.a), bentazon (720 g ha-1 de i.a), bentazon + imazamox (600 + 28 g ha-1 de i.a), fluazifop-p-buthyl + fomesafen (250 +250 g ha-1 de i.a), seguidos de mais duas testemunhas, uma capinada e outra infestada. O oxifluorfen apresentou os maiores níveis de fitotoxicidade ao feijoeiro cultivar BRS Campeiro, o que resultou no efeito negativo sobre os componentes do rendimento de grãos, juntamente com a testemunha infestada, o s-metolachlor, o pendimentalin, o flumioxazin, o fomesafen e o bentazon. A mistura comercial composta de bentazon + imazamox apresentou baixa fitotoxicidade, os melhores resultados em relação aos componentes do rendimento de grãos, aliado a um bom controle da milhã e do papuã.

Weeds as the potential inoculum source of Colletotrichum fructicola responsible for strawberry anthracnose in Nara, Japan

Colletotrichum fructicola is a major causal agent among anthracnose pathogens of strawberry in Nara, Japan. We hypothesized that a wide range of weeds growing in and around strawberry fields are inoculum sources of the disease and investigated their potential as hosts of C. fructicola. We also examined the influence of herbicide treatment on C. fructicola sporulation on weeds. The fungus was detected on 31 of 541 (5.7%) leaves sampled from 13 weed species from 2005 to 2008. The fungus was most frequently isolated from leaves of Amaranthus blitum with an isolation frequency of 17.9%; inoculation of A. blitum with the pathogen caused brown leaf spots. Other weeds such as Digitaria ciliaris, Galinsoga ciliata, Solidago altissima, Erigeron annuus, and Sonchus oleraceus were found to harbor the fungus at lower rates (4.3–8.1%) without symptoms. C. fructicola formed acervuli on leaves of A. blitum, D. ciliaris, and S. oleraceus after plants were killed by a herbicide (glyphosate). These results demonstrated that infected weeds associated with strawberry cultivation are potential inoculum sources of C. fructicola, especially after herbicide treatment.

토양 방선균 Actinomycetes G-0299의 바랭이에 대한 선택적 살초특성

An actinomycetes isolate G-0299 obtained from a forest soil showed strong phytotoxic activity to Digitaria ciliaris. For the foliar application study, the culture filtrate of the isolate G-0299 showed strong herbicidal activity only to D. ciliaris among the 12 monocot and 5 dicot weed species. And herbicidal activity at a concentration of 500, 250, 125 and 62.5 μg mL -1 of culture filtrate was 100%, 98%, 70% and 40%, respectively. Phytotoxic symptoms of the culture filtrate by foliar application were desiccation and burn-down or bleaching of leaves and finally plant death. And then the herbicidal activity was exhibited only under the light condition. Also, chlorophyll loss of D. ciliaris leaf tissues in the light condition was much higher than in the dark condition and then chlorophyll content decreased 82%, 5%, respectively. In conclusion, our results suggest that soil bacteria, isolate G-0299 could be a good candidate for new bio-herbicide and provide a new lead molecule for a more unique herbicide.

Evaluating sampling strategy for DNA barcoding study of coastal and inland halo-tolerant Poaceae and Chenopodiaceae: A case study for increased sample size.

Environmental conditions in coastal salt marsh habitats have led to the development of specialist genetic adaptations. We evaluated six DNA barcode loci of the 53 species of Poaceae and 15 species of Chenopodiaceae from China's coastal salt marsh area and inland area. Our results indicate that the optimum DNA barcode was ITS for coastal salt-tolerant Poaceae and matK for the Chenopodiaceae. Sampling strategies for ten common species of Poaceae and Chenopodiaceae were analyzed according to optimum barcode. We found that by increasing the number of samples collected from the coastal salt marsh area on the basis of inland samples, the number of haplotypes of Arundinella hirta, Digitaria ciliaris, Eleusine indica, Imperata cylindrica, Setaria viridis, and Chenopodium glaucum increased, with a principal coordinate plot clearly showing increased distribution points. The results of a Mann-Whitney test showed that for Digitaria ciliaris, Eleusine indica, Imperata cylindrica, and Setaria viridis, the distribution of intraspecific genetic distances was significantly different when samples from the coastal salt marsh area were included (P < 0.01). These results suggest that increasing the sample size in specialist habitats can improve measurements of intraspecific genetic diversity, and will have a positive effect on the application of the DNA barcodes in widely distributed species. The results of random sampling showed that when sample size reached 11 for Chloris virgata, Chenopodium glaucum, and Dysphania ambrosioides, 13 for Setaria viridis, and 15 for Eleusine indica, Imperata cylindrica and Chenopodium album, average intraspecific distance tended to reach stability. These results indicate that the sample size for DNA barcode of globally distributed species should be increased to 11–15.

Dimethenamid Persistence and Leaching Potential in a Soilless Mix1

Abstract Dimethenamid and the granular combination product pendimethalin plus dimethenamid are herbicides registered for use in nursery production and landscape maintenance. The objectives of this study were: (1) to compare the effectiveness of sprayed dimethenamid and the granular combination of pendimethalin plus dimethenamid in container nursery production, (2) to determine the impact of formulation on leaching of dimethenamid in soilless media versus field soil and (3) to determine the influence of irrigation volume on herbicide leaching. Dimethenamid is less mobile in pine bark than field soil, while pendimethalin is more mobile in pine bark. The leaching profile for the granular pendimethalin plus dimethenamid combination product was similar to dimethenamid in field soil and similar to pendimethalin in pine bark. There was no significant difference in herbicide movement in pine bark or field soil after doubling the irrigation volume from 17.8 cm (7 in) to 35.6 cm (14 in). Compared to pendimethalin, dimethenamid leaches less in pine bark, explaining its greater effectiveness for weed control in container production. Index words: Herbicide leaching, soilless mix, pine bark, ornamentals, adsorption. Species used in this study: southern crabgrass [Digitaria ciliaris (Retz.) Koel.]; spotted spurge [Chamaesyce maculata (L.) Small]. Chemicals used in this study: dimethenamid (Tower); dimethenamid plus pendimethalin (FreeHand); pendimethalin (Pendulum 2G).

Associação de herbicidas aplicados para o controle de plantas daninhas em soja resistente ao glyphosate

Para contornar os casos de plantas daninhas resistentes ao glyphosate torna-se necessário o uso de herbicidas com outros mecanizamos de ação. Objetivou-se com o trabalho avaliar a eficácia e a seletividade de herbicidas aplicados isolados ou em mistura de tanque para o manejo de plantas daninhas infestante da soja resistente ao glyphosate. Os tratamentos foram aplicados de forma sequencial, em pré-emergência: clomazone (900 g ha-1 i.a.); flumioxazin (50 g ha-1 i.a.); diclosulam (35,02 g ha-1 i.a.); s-metolachlor (1152 g ha-1 i.a.); sulfometuron + chlorimuron-ethyl (18,75 + 18,75 g ha-1 i.a.); pendimethalin (1250 g ha-1 i.a.); sulfentrazone (250 g ha-1 i.a.); sulfentrazone + chlorimuron-ethyl (250 + 20 g ha-1 i.a.); imazethapyr + sulfentrazone (100 + 250 g ha-1 i.a.) e imazaquin (150 g ha-1 i.a.) e em pós-emergência sobre esses mesmos tratamentos usou-se o glyphosate (1080 g ha-1 e.a.). Em pós-emergência aplicou-se de modo isolado o glyphosate (1080 g ha-1 e.a.) e misturados ao tanque do pulverizador com glyphosate (1080 g ha-1 e.a.), imazethapyr (100 g ha-1 i.a.), clethodim (96 g ha-1 i.a.) e chlorimuron-ethyl (20 g ha-1 i.a.), mais as testemunhas infestada e capinada. A área experimental estava infestada com uma porcentagem de 75% de plantas de papuã (Urochloa plantaginea) e 25% com plantas de milhã (Digitaria ciliaris), nas densidades médias de 133 e 45 plantas m-2, respectivamente. Aos 14 e 21 dias após a aplicação dos tratamentos (DAT) a aplicação de glyphosate + [sulfometuron + chlorimuron-ethyl] ocasionou fitotoxicidade à soja de 67 e 62% respectivamente. Para o controle de milhã e papuã essa mesma mistura apresentou índice de 88% aos 21 DAT, sendo que o controle para os demais tratamentos ultrapassou os 91% em todas as épocas avaliadas. Todos os tratamentos avaliados ocasionaram controle das duas plantas daninhas maior que 91%, exceto o glyphosate + [sulfometuron + chlorimuron-ethyl]. As associações dos herbicidas ao glyphosate ocasionaram controle das plantas daninhas e foram seletivas a soja, com exceção do sulfometuron + chlorimuron-ethyl, que apresentou menor controle e elevada fitotoxicidade. Alguns herbicidas prejudicaram os componentes de rendimento da soja, porém somente a mistura de sulfometuron + chlorimuron-ethyl apresentou diminuição da produtividade de grãos.

Determining the Microwave Radiations Exposure Level Needed for Weed Control Using a Stationary and Running Belt Microwave Radiations Applicator System1

Abstract There is a demand for nonchemical weed control strategies, with microwave radiations one possible option. Accurately measuring a weed's exposure level to microwave radiations is a challenge when there is a gap between when electricity is applied to the magnetron and actual production of microwave radiations. This gap causes an error in the calculation of actual energy needed for weed management. Any misinterpretation over-estimates the required energy load, adversely affecting the perceived value of the technology. Studies were conducted to eliminate the existing lag period. A running belt prototype was built for this purpose using two magnetrons producing 900 watt each installed on a treadmill with a power supply. There was significant improvement in the precision for calculations of total energy required for weed control. These anatomically diverse weeds showed more uniform thermal injuries and greater control using the running belt prototype system than a stationary unit. The LD50 for broadleaf weeds treated with microwave radiations using the running belt system ranged from 31.2 joules.cm−2 for common ragweed (Ambrosia artemisiifolia L.) to 36.8 joules.cm−2 for pitted morningglory (Ipomoea lacunosa L.). In comparison, treatment of weeds with microwave radiations using the stationary mode system resulted in a range of LD50 values of 64.5 joules.cm−2 for common ragweed to 155.1 joules.cm−2 for white clover (Trifolium repens L.). Similarly, the LD50 values for grasses treated with microwave radiations using the running belt system ranged from 34.3 for dallisgrass (Paspalum dilatatum Poir.) to 69.5 joules.cm−2 for southern crabgrass [Digitaria ciliaris (Retz.) Koeler]); in comparison, the range in LD50 values for grasses treated with stationary system was 136.1 to 182 joules.cm−2. The LD50 values for sedges treated with microwave radiations using the running belt system ranged from 29.2 joules.cm−2 for yellow nutsedge (Cyperus esculentus L.) to 78.1 joules.cm−2 for fragrant flatsedge (Cyperus odoratus L.); in comparison, the range in LD50 values for the stationary mode system was 119.4 joules.cm−2 for fragrant flatsedge to 145.9 joules.cm−2 for yellow nutsedge. Index words: Nonchemical control, weed control, efficacy, prototype, weed management.

Relative time of weed and crop emergence is crucial for managing weed seed production: A study under an aerobic rice system

Managing weed seed production may help in reducing weed emergence and biomass in successive seasons in dry-seeded rice. Field experiments were conducted in 2012 and 2013 to ascertain the effect of delayed weed emergence, i.e., 0, 14, 28, 42, 56, and 70 days after sowing (DAS) on seed production ability of Digitaria ciliaris and Echinochloa crus-galli in two rice cultivars (PR115 with 125 days duration and PR114 with 145 days duration). Emergence of E. crus-galli was similar in both the cultivars, except at 42 DAS, where the emergence was higher in PR114 than PR115 during 2012. In PR114, D. ciliaris continued to emerge up to 56 DAS, although the increase was significant up to 28 DAS; the increased emergence of this weed was noticed up to 14 DAS in PR115. Weed biomass was also higher in PR114, although the rate of the decrease with respect to emergence time was similar in both the rice cultivars. D. ciliaris, when emerged with the crop, produced 11,820 seeds per plant in PR114, but seed production reduced by 25% in PR115. However, differences in seed production of E. crus-galli were noticed when this weed emerged between 14 and 42 DAS. An exponential model predicted that, for a 99% reduction in seed production of D. ciliaris, 42–45 days of crop advancement, while, for E. crus-galli, 21–33 days of crop advancement was required. Our study suggests that delaying the weed emergence in the crop and/or adopting better competitive rice cultivars can reduce the weed seed production substantially.

Soil heavy metal contamination and health risks associated with artisanal gold mining in Tongguan, Shaanxi, China

Soil contamination with heavy metals due to mining activities poses risks to ecological safety and human well-being. Limited studies have investigated heavy metal pollution due to artisanal mining. The present study focused on soil contamination and the health risk in villages in China with historical artisanal mining activities. Heavy metal levels in soils, tailings, cereal and vegetable crops were analyzed and health risk assessed. Additionally, a botany investigation was conducted to identify potential plants for further phytoremediation. The results showed that soils were highly contaminated by residual tailings and previous mining activities. Hg and Cd were the main pollutants in soils. The Hg and Pb concentrations in grains and some vegetables exceeded tolerance limits. Moreover, heavy metal contents in wheat grains were higher than those in maize grains, and leafy vegetables had high concentrations of metals. Ingestion of local grain-based food was the main sources of Hg, Cd, and Pb intake. Local residents had high chronic risks due to the intake of Hg and Pb, while their carcinogenic risk associated with Cd through inhalation was low. Three plants (Erigeron canadensis L., Digitaria ciliaris (Retz.) Koel., and Solanum nigrum L.) were identified as suitable species for phytoremediation.

Performance of Heifers Grazing Bermudagrass Pastures Strip or Solid Seeded with Clovers

Core Ideas Strip‐seeding of clovers into bermudagrass swards resulted in similar clover stand percentage compared with solid planting of clovers. Heifers grazing pastures that were strip seeded performed similarly to heifers grazing clovers that were seeded in solid stands. Red clovers persisted longer into the summer than either white or subterranean clovers. Red clover provided greater animal performance than white and subterranean clovers. Even though clovers can provide improved forage quality and reduced N fertilization when grazing stocker calves on warm‐season grass pastures, stand establishment remains a concern. The objective of this research was to determine if alternative methods of seeding legumes into warm‐season perennial swards could improve legume establishment. This research took place on 18, four‐acre mixed bermudagrass [Cynodon dactylon (L.) Pers.], crabgrass [Digitaria ciliaris (Retz.) Koeler], and dallisgrass (Paspalum dilatatum Poir.) pastures at the University of Arkansas Southwest Research and Extension Center Stocker Unit. Pastures were seeded in October of 2013 to white (Trifolium repens L.), red (Trifolium pratense L.), or subterranean (Trifolium subterraneum L.) clovers either in solid stands at the recommended rate (2.0, 8.0, and 11 lb/acre, respectively) or in four 0.25‐acre strips at twice the recommended seeding rate in a 3 × 2 factorial arrangement of treatments with three pasture replications per treatment combination. Growing heifers (n = 216; 614 ± 44.4 lb) grazed pastures from May to September 2014 and April to September 2015. Red clover was present later into the summer than white or subterranean clovers, but there were no differences due to seeding method. At the end of the grazing season, heifer bodyweight and gain was greater when grazing red clover than when grazing subterranean clover. Strip‐seeded clovers in only 50% of the pasture area provided similar stands to conventional solid seeding and equivalent animal performance. Red clover grew later into the summer grazing season and provided greater animal performance than white and subterranean clovers.

First Report of Acetyl-CoA Carboxylase–Resistant Southern Crabgrass (Digitaria ciliaris) in the United States

Two populations of southern crabgrass identified in Georgia turfgrass were suspected to be resistant to sethoxydim. The objectives of this research were to evaluate the resistance levels of these biotypes to acetyl-CoA carboxylase (ACCase) inhibitors and alternative herbicides for control. From dose response experiments, the sethoxydim rate required to reduce shoot biomass 50% from the nontreated measured &gt;64-times greater for both resistant (R) biotypes compared to the susceptible (S) biotype. Both R biotypes were cross-resistant to fenoxaprop and fluazifop. Clethodim at 290 gaiha−1reduced dry shoot biomass of the R biotypes and the S biotype to 47 and 21% of the nontreated, respectively. The R biotypes were equally susceptible to MSMA at 2240 g ai ha−1, quinclorac at 840 g ai ha−1, and topramezone at 37 g ai ha−1as compared to the S biotype. Sethoxydim at 315 and 945 g ha−1provided &lt;20% control of the southern crabgrass populations in four field experiments. However, clethodim and topramezone provided 83% and 76% control at 4 wks after treatment, respectively. These southern crabgrass biotypes are resistant to sethoxydim and aryloxyphenoxypropionate herbicides. Although the R biotypes were less susceptible to clethodim than the S biotype, treatments provided acceptable control in the field. This is the first report of ACCase-resistant southern crabgrass in the United States.

Sensitivity of recently naturalised Digitaria spp. populations to 4‐hydroxyphenyl pyruvate dioxygenase‐ and acetolactate synthase‐inhibiting herbicides in maize

SummaryUntil recently, Digitaria aequiglumis var. aequiglumis, native to South America, and Digitaria ciliaris subsp. nubica, native to Northeast Africa, were completely overlooked in Belgium due to their close morphological resemblance to Digitaria sanguinalis and Digitaria ischaemum. One of the possible reasons for their expansion in maize fields, besides for example the lack of crop rotation, might be a lower sensitivity to post‐emergence herbicides acting against panicoid grasses. Dose–response pot experiments were conducted in the glasshouse to evaluate the effectiveness of four foliar‐applied HPPD‐inhibiting herbicides (mesotrione, sulcotrione, tembotrione, topramezone) and two foliar‐applied ALS‐inhibiting herbicides (foramsulfuron, nicosulfuron) for controlling Belgian populations of D. aequiglumis and D. ciliaris subsp. Nubica, as well as local D. sanguinalis and D. ischaemum populations. In another dose–response pot experiment, the influence of growth stage at time of herbicide application on efficacy of topramezone and nicosulfuron for Digitaria spp. control was evaluated. In general, D. aequiglumis and D. ciliaris subsp. nubica populations were less sensitive to HPPD inhibitors than D. ischaemum and D. sanguinalis populations, except for D. aequiglumis treated with topramezone. Contrary to other herbicides tested, topramezone adequately controlled all D. aequiglumis populations at doses well below maximum authorised field dose. All species tested showed a progressive decrease in sensitivity to topramezone and nicosulfuron with seedling age. A satisfactory post‐emergence control of Digitaria species in the field will require appropriate choice of herbicide and dose, as well as more timely application.