Pre-emergence Application Research Articles

Efficacy of new generation herbicidal combination for weed management in direct seeded rice (Oryza sativa L.)

Weeds are the main yield limiting factor that can potentially reduce crop yields and is one of the main constraints in the larger scale implementation of direct seeded rice. Therefore, the present experiment was conducted at Periyanarkunam during Navarai 2021 to study the efficacy of new generation herbicidal combination for weed management in direct seeded rice. The experiment was laid out in split plot design replicated thrice with main plot treatments comprised of three direct seeded rice establishment methods viz., dry seeded, drum seeded and manual wet seeded rice. The sub-treatments were nine weed management practices with combination of herbicides with hand weeding viz., Pre-emergence application of bensulfuron methyl 0.6%+pretilachlor 6% GR @ 10 kg/ha on 8 DAS (Days after sowing), early post- emergence application of triafamone 20%+ethoxysulfuron 10% WG @ 200 g/ha on 12 DAS, post-emergence application of metsulfuron methyl 10%+chlorimuron ethyl 10% @ 20 g/ha on 25 DAS, twice hand weeding on 25 and 45 DAS and un-weeded check. Among the main treatments, drum seeded rice recorded lower weed population and dry matter production, higher weed control efficiency, weed control index, crop resistance index and herbicide efficiency index and higher grain yield which was at par with manual wet seeded rice. Regarding the weed management practices evaluated pre-emergence application of bensulfuron methyl 0.6%+pretilachlor 6% GR @ 10 kg/ha on 8 DAS fb (followed by) post-emergence application of metsulfuron methyl 10%+chlorimuron ethyl 10% @ 20 g/ha on 25 DAS fb hand weeding on 45 DAS (S8) registered lower weed population, dry matter and higher yield compared to unweeded check. Hence, drum seeded rice coupled with pre-emergence application on 8 DAS fb post-emergence application on 25 DAS fb hand weeding on 45 DAS (M2S8) is an economically feasible method for effective control of weeds.

Yield enhancement in sesame (Sesamum indicum L.) var. TMV 7 through weed management practices

A field experiment was conducted during summer season of 2021 with a view to find out a suitable weed management practice for sesamum by excluding commonly used herbicides and including botanical herbicides along with hand weeding. The experiment was conducted in randomized block design with 10 treatments and was replicated thrice. The treatments included one pre-emergence herbicide metribuzin at two levels, one early post- emergence herbicide imazethapyr and one post-emergence herbicide quizalofop ethyl and were applied individually and in sequence along with HW. Two plant products Ageratum conizoides and Ocimum sanctum were tried each at two levels along with HW. These treatments were compared with twice HW and unweeded control. Among the treatments, the least weed density (9.92, 9.88), weed DMP (4.96, 13.54 g/m2), highest grain yield (684 kg/ha) and stalk yield (2069 kg/ha) were recorded in pre-emergence application of metribuzin @ 100 g a.i./ha on 3 DAS+Early post-emergence application of imazethapyr @ 30 g a.i./ha on 10 DAS+HW on 20 DAS. Further, this treatment gave the highest BCR of 2.46. Treatments involving herbicides fb HW were better than plant products fb HW treatments in terms of weed density and yield.

Studies on Nutrient and Weed Dynamics on Growth and Yield Attributes of Direct Seeded Rice

Field experiment was carried out during kharif 2020 and 2021 at wetland farm of S. V. agricultural College, Tirupati, Andhra Pradesh. The experiment was laid out in a split plot design with three replications. The treatments consisted of three main plots viz., 100 % RDF (N1), 125 % RDF (N2) and 150 % RDF (N3) and five sub plots viz., Pre emergence (PE) application of pyrazosulfuron-ethyl 25 g ha-1 fb penoxsulam + cyhalofop-p-butyl 125 g ha-1 at 20 DAS (W1), Pre emergence (PE) application of pyrazosulfuron-ethyl 25 g ha-1 fb florpyrauxifenbenzyl + cyhalofop-p-butyl 150 g ha-1 at 20 DAS (W2), Pre emergence (PE) application of pyrazosulfuron-ethyl 25 g ha-1 fb bispyribac-sodium 20 g ha-1 at 20 DAS (W3), hand weeding twice at 20 and 40 DAS (W4) and unweeded check (W5). Nutrient levels and weed management practices significantly influenced the growth parameters viz., plant height, number of tillers m-2 and dry matter production and yield attributes viz., number of panicles m-2, total number of grains panicle-1 and number of filled grains panicle-1 of direct seeded rice during both the years of investigation as well as in pooled mean. Interaction effect due to nutrient levels and weed management practices on growth parameters and yield attributes was found to be significant during both the years of study and in the pooled mean.

HPPD-resistant cotton response and weed management systems using isoxaflutole

AbstractThe southern United States produces 90% of the nation’s cotton, and the Texas High Plains is the largest contiguous cotton producing region. Since 2011, glyphosate-resistant Palmer amaranth has complicated cotton production, and alternatives to glyphosate are needed. Integrating soil residual herbicides into a weed management program is a crucial step to control glyphosate resistant weeds before emergence. The recent development of p-hydroxyphenylpyruvate dioxygenase (HPPD)-resistant cotton by BASF Corporation may allow growers to use isoxaflutole in future weed management programs. In 2019 and 2020, field experiments were conducted in New Deal, Lubbock, and Halfway, Texas, to evaluate HPPD-resistant cotton response to isoxaflutole applied preemergence (PRE) or early postemergence (EPOST) and to determine the efficacy of isoxaflutole when used as part of a season-long weed management program. At the New Deal location, cotton response was observed following the EPOST application, but it never exceeded 10%. Cotton response was greatest following the PRE application in Lubbock in 2019 but did not exceed 14%. In 2020 in Lubbock, cotton was replanted due to severe weather. There was <1% cotton response following the PRE application, and maximum cotton response observed was 9% following EPOST and mid-postemergence (MPOST) applications. Cotton lint yields were not different from those of the nontreated, weed-free control at either location. In non-crop weed control studies in Halfway, all treatments controlled Palmer amaranth ≥94% 21 d after the EPOST application. Twenty-one days after the MPOST treatment, systems with isoxaflutole applied EPOST controlled Palmer amaranth by 88% to 93%, while systems with isoxaflutole PRE controlled Palmer amaranth by 94% to 98%. End-of-season Palmer amaranth control was lowest in the system without isoxaflutole (88%) and when isoxaflutole was used EPOST (88% to 91%). These studies suggest that the use of isoxaflutole in cotton weed management systems may improve season-long control of several troublesome weeds with no adverse effects on cotton yield and quality.

Integration of Halosulfuron and Anaerobic Soil Disinfestation for Weed Control in Tomato

Anaerobic soil disinfestation (ASD) is a preplant pest management technique that involves amending the soil with a labile carbon source, irrigating the soil to stimulate decomposition, and then covering the soil with polyethylene film (polyfilm) to limit gas exchange. During the ASD process, soil microorganisms shift from aerobic to anaerobic metabolism and release phytotoxic byproducts such as organic acids and gases. Although it has been shown that these phytotoxic by-products have a negative impact on weed survival, questions remain about whether commercial-level weed control can be achieved using ASD alone or in combination with other chemicals. Greenhouse and field studies were conducted to evaluate ASD with mustard (Brassica sp.) meal, molasses, and herbicide applications for yellow nutsedge (Cyperus esculentus) control in tomato (Solanum lycopersicum). The treatments in these studies included factorial of two carbon sources [mustard meal + molasses (MMM) or no carbon amendment], three herbicide treatments [halosulfuron applied preemergence (PRE), halosulfuron applied postemergence (POST), and no herbicide] and two polyfilm treatments (polyfilm cover or polyfilm uncover). In field trials two polyfilm cover treatments were punctured and nonpunctured. Soil treatments included molasses at 14,000 L·ha−1 and mustard meal at 2100 kg·ha−1. Halosulfuron was applied at a rate of 1 oz/acre for PRE or POST applications. Greater anaerobic conditions were achieved in polyfilm cover treatments amended with MMM. In greenhouse and field trials, the most effective treatments for reducing yellow nutsedge populations were ASD with MMM or combined with halosulfuron application (PRE- or POST-ASD), which delivered significantly higher weed control than all other treatments tested or controls. In field trials, ASD with MMM caused plant growth stunting 14 d after transplantation (DAT); however, plants recovered, and stunting or injury was often not observed at 42 DAT. These studies demonstrated that ASD using MMM can be an effective strategy for reducing yellow nutsedge populations; however, the more research is needed to ensure crop safety while using ASD technology.

Impact of Chemical Weed Management Practices on Yield, Nutrient Uptake and Balance in Soil of High Density Planting Cotton in Deep Vertisols

In order to assess Clomazone 50 EC's effectiveness on seed cotton yield, nutrient uptake, and balance in HDPS cotton in deep Vertisols of the Northern Karnataka region, a field experiment was carried out in 2017–18 and 2018–19. The recommended course of treatment includes pre-emergence applications of Clomazone 50 EC at 250, 500, and 750 g a.i./ha compared to pendimethalin 37.5 CS@680 g a.i./ha, post-emergence applications of pyrithiobac sodium 10 EC and quizalofop ethyl hand weeding at 25 DAS and intercultivation at 50 and 75 days after sowing, as well as weed free. The experiment was set up using a randomised block design with triple replication. The application of Clomazone 50 EC @ 250 g a.i./ha was found to be effective in weed control and enhanced seed cotton yield (38.5%), according to the results. It led to excellent weed control, decreased nitrogen uptake by weeds, and increased nutrient uptake by the crop. Additionally, it leads to the least amount of nutrient losses in terms of uptake and losses. In order to effectively manage weeds in cotton, it was observed that Clomazone 50 EC @ 250 g a.i/ha, followed by pyrithiobac sodium 10 EC @ 75 g a.i./ha + Quizalofop ethyl 5 EC @ 75 g a.i./ha at 25 DAS, were the best applications.

Herbicide control of Ambrosia artemisiifolia in sunflower, soybean and maize

Abstract Ambrosia artemisiifolia L. (Asteraceae) has become a major threat to agriculture in many parts of the world. Global agriculture relies on the use of herbicides against A. artemisiifolia in the crops most at risk – sunflower, maize and soybean. This paper aims to provide an overview of the chemical control of A. artemisiifolia and to summarize the latest knowledge in this field. The sunflower is the crop most threatened by A. artemisiifolia, as both plants belong to the same family. The best control level was achieved after the preemergence application of flurochloridone and the combination of dimethenamid-P + pendimethalin. The introduction of the non-GM Clearfield and ExpressSun technologies allowed effective control with postemergence herbicides in sunflower varieties tolerant to imidazolinone and tribenuron-methyl herbicides. In soybean, the highest efficacy was observed in trials with imazamox and bentazone alone and in combination. The combination of imazamox with bentazone had a positive effect on yield compared to untreated stands. The introduction of transgenic soybeans tolerant to glyphosate led to increased glyphosate use and the predictable emergence of weed resistance in America in 1996. Preplant followed by postemergence herbicides were critical for the effective control of glyphosate-resistant A. artemisiifolia in glufosinate tolerant soybean. In maize, the highest efficacy was obtained after the application of glufosinate, bromoxynil and mesotrione + atrazine. Of the above substances for the control of A. artemisiifolia in maize, only mesotrione is currently registered in the EU.

Weed seed bank and weed population as influenced by weed management practices in rice var Co 54

Weed seed bank in soil serves as the reservoir of weed seeds which emerge whenever conditions become conducive and affects crop growth. In the present study, a field experiment was performed at Agricultural College and Research Institute, Tamil Nadu Agricultural University, Madurai, India, during Kharif 2021 and Rabi 2022 to determine weed seed bank present in soil by direct seed extraction using the sieving method at discrete depths of 0-5 cm, 5-10 cm and 10-15 cm after rice harvest with reference to different weed management practices imposed and its effect on weed population in succeeding crop. The average proportion of weeds that emerged in the field ranged from 9 to 38 % of the total weed seed bank. Weed management practices followed during the preceding crop greatly influenced weed seed germination. The higher weed seed reserve (1384 m-2) and consequent weed population (528 no’s m-2) were found at a depth of 0-5 cm in unweeded plots. The lower weed seed density (536 m-2) and weed population (94 no’s m-2) were found in pre emergence application of Pyrazosulfuron + Pretilachlor and early post emergence application of Bispyripac sodium. The results from the present study confirmed that herbicide treatment considerably minimized the weed seed density and population, which will assist in predicting weed infestation and appropriate timing of weed control.

Effect of polymer seed coating with pendimethalin on germination percentage and growth characters of aerobic rice

Weeds are the major constraints in aerobic rice cultivation which provides stronger competition for essential growth factors. As one of the weed control techniques, we used polymer seed coating with herbicide as a seed treatment before sowing as an alternative to pre-emergence application of herbicide. The present investigation was carried to study the effect of polymer seed coating with pendimethalin on germination percentage and growth characters of rice in Department of Agronomy, Tamil Nadu Agricultural University, Coimbatore. The experiment comprised of pot culture studies and germination test. Initially the seed were treated with polymer @ 3ml/kg of seed, this base layer provided a surface for adhesion of herbicide and added the pendimethalin with different concentrations ranging from 0.4 to 1.0 kg a.i./ha. The results revealed that Polymer seed coating with pendimethalin had negative effect on emergence of paddy seeds due to its phytotoxicity and the seed coating with polymer alone does not have any effect on the emergence and development of rice.

Influence of insecticide spray regime and weed management methods on growth and yield of cowpea

ABSTRACT Cowpea (Vigna unguiculata L. Walp.) production in Nigeria is limited mainly due to weed and insect infestations. The effects of insecticide spray regime and weed control on the productivity of cowpea were evaluated in the early and late seasons of 2020. Two insecticide sprays produced increased growth and yield in the late cropping season. However, in the early cropping season, optimum growth and yield of cowpea were obtained with four insecticide sprays. Regardless of the cropping season, preemergence (PRE) application of metolachlor or propaben plus manual weeding (MW) provided 71–80% reduction in weed density and biomass and resulted in cowpea growth and yields similar to the weed-free control. In the late season, two MWs resulted in cowpea growth and yield similar to the weed-free control. However, in the early season treatment, two MWs resulted in 51% lower yield than the weed-free control. The results showed that four insecticide sprays in the early cropping season or two insecticidal sprays in the late cropping season integrated with metolachlor or propaben application plus MW improved the productivity of cowpea.

Screening of Effective Leaf Extracts for Weed Management in Little Millet (Panicum sumatrense Roth ex Roem. & Schult)

Field experiment was conducted at Tamil Nadu Agricultural University, Coimbatore in January 2022 by seven different leaf extracts as an allelopathical compound in order to choose the best alternative to chemical herbicides by non-chemical weed management approach in little millet owing to the great surge of organic farming in millet production nowadays. Screening trail has been conducted to observe the effect of leaf extracts (Tamarind,Casuarina,Castor,Papaya, Teak,Pine,Nerium) with 20 & 30% concentration on weed control. This experiment laid out in a randomized block design and was replicated twice with 15 different treatments. The findings of this investigation demonstrated that the pre emergence (3 DAS) application of Tamarind leaf extract (30%), Casuarina leaf extract (30%). Castor leaf extract (30%). Papaya leaf extract (30%). Teak leaf extract (30%). Pine leaf extract (30%) and Nerium leaf extract (30%) pronounced the lowest weed density and highest weed control efficiency among fifteen treatments. Based on the results of the experiment, it was concluded that pre emergence application of any different leaf extract among the fifteen treatments, Tamarind, Casuarina, Castor, Papaya, Teak, Pine, and Nerium leaf extracts with 30% concentration had found the allelopathic potential to reduce the weed density and recorded high weed control efficiency with no phytotoxicity on the little millet.

Evaluation of amino acid–inhibiting herbicide mixtures for hair fescue (Festuca filiformis) management in lowbush blueberry

AbstractHair fescue is a perennial grass weed in lowbush blueberry fields that forms dense sods and reduces yield. As a result of natural tolerance or resistance of this grass to other currently registered herbicides growers rely on preemergence (PRE) applications of pronamide and postemergence (POST) applications of the Group 2 herbicides foramsulfuron and nicosulfuron + rimsulfuron for hair fescue management. This causes repeated application of Group 2 herbicides, which is compounded by the recent registration of flazasulfuron for POST suppression of hair fescue in lowbush blueberry. Mixtures of Group 2 herbicides with the amino acid–inhibiting herbicides glyphosate (Group 9) and glufosinate (Group 10), however, can improve weed control and may delay herbicide resistance development. This research used a factorial arrangement of Group 2 herbicides (none, foramsulfuron [35 g ai ha−1], nicosulfuron + rimsulfuron [13 + 13 g ai ha−1], flazasulfuron [50 g ai ha−1]) and mixtures (none, with glyphosate [902 g ae ha−1], and with glufosinate [750 g ai ha−1]) to identify possible mixtures that improve weed control and delay resistance development. Herbicides were applied in spring nonbearing year, fall bearing year, and fall nonbearing year, with each application timing conducted as a separate experiment. Foramsulfuron and nicosulfuron + rimsulfuron were not effective as fall applications, and spring applications of these herbicides with glyphosate or glufosinate improved hair fescue suppression. Glyphosate and glufosinate were more effective as fall rather than spring applications. Flazasulfuron was effective across all application timings, although its mixture with glufosinate generally improved hair fescue suppression. Flazasulfuron + glufosinate is tentatively recommended as an effective mixture for management of spring nonbearing-year and fall bearing-year hair fescue in lowbush blueberry.

Effect of weed control treatments and planting method on the yield and yield parameters of rice in Sudan savannah of Nigeria.

The experimentswerecarried out in 2020 and 2021 rainy seasons to determine the performance ofrice as influenced by planting method and weed control treatments. The treatments consists of three planting methods (dibbling broadcasting and transplanting and weed control methods (hoe weeding, pre emergence application of gramazone (200g/L of paraquat/ha), pre and post emergence of gramazone (200g/L of paraquat/ha) and propanil (360g/L of propanil + 200g/L 2-4D) and weedy check). The treatments were laid out in a randomized complete block design (RCBD) and were replicated three times.The results revealed the plots weeded twice and those treated with pre and post emergence application of gramazone and propanil respectively resulted in more number of spikelet per panicle, longer panicle, increase in number of effective tillers per hill, more grains per panicle and grain yield. The effect of planting methods on the rice growth revealed that rice sown under transplanting methods gave more number of effective tiler per hill, longer panicle, more grain per panicle and increases in grain yield compared to the others methods while broadcasting resulted in the least value of the parameters than others methods.Therefore,it can be concluded that rice farmers in the sudan savanna zone of Nigeria can adoptpre and post emergence application of gramazone and propanil with transplanting method since the combination of these treatments gave better weed control, growth and yield of paddy rice. Key words: Herbicide, length of panicle, number of grain per panicle andgrain yield

Effect of new generation herbicides on mixed weed flora and yield of direct seeded rice (Oryza sativa L.)

A field experiment was conducted during the “Navarai” season of 2019 and 2020 at Experimental Farm of the Department of Agronomy, Annamalai University, Annamalai Nagar, to find out the effect of new generation herbicides on direct seeded rice (Oryza sativa L.). The herbicide used were pre-emergence application of pyrazosulfuron-ethyl 10% WP at 200 g ha-1, pre-emergence application of metsulfuran-methyl 10% + chlorimuron-methyl 10% WP at 20g ha-1, pre-emergence application of pretilachlor 50% EC at 1250 ml ha-1, Early post-emergence application of pretilachlor 6% + pyrazosulfuran-ethyl 0.15% G at 615g ha-1, Early post-emergence application of bispyribac-sodium at 300 ml ha-1. The experimental result revealed that the new generation herbicide has a significant influence on weed flora and yield attributes and yield of direct seeding rice. The result indicated that application of Bispyribac-sodium 10% SC at 300 ml ha-1 at 15 DAS + one Hand weeding at 30 DAS recorded the lowest weed population, weed dry matter production and higher weed control index (WCI) and yield. Then twice hand weeding at 15, and 30 DAS was next in order. The lowest weed control index and yield were recorded with un-weeded control.

Investment Returns for Preemergence Herbicide Use in No-till Pumpkin

Preemergence (PRE) herbicides are an important part of the overall weed management plan in no-till (NT) pumpkin (Cucurbita pepo) production. A field evaluation was conducted in an NT production system using PRE herbicides labeled for pumpkins to determine the benefits of specific herbicide combinations and the economic returns on investment associated with their use. The PRE herbicide treatments evaluated were 1) s-metolachlor (1360 g⋅ha–1 a.i.), 2) clomazone (350 g⋅ha–1 a.i.) and ethalfluralin premix (1120 g⋅ha–1 a.i.), 3) s-metolachlor + clomazone and ethalfluralin premix, 4) s-metolachlor + halosulfuron (35 g⋅ha–1 a.i.), 5) clomazone and ethalfluralin premix + halosulfuron, and 6) none. The primary weed species present were tall waterhemp (Amaranthus tuberculatus), redroot pigweed (Amaranthus retroflexus), giant foxtail (Setaria faberi), and large crabgrass (Digitaria sanguinalis). The best weed control option for full-season broadleaf and grass weed control was s-metolachlor + clomazone and ethalfluralin. This herbicide combination also provided the greatest economic return on investment, ranging from a 20% to 40% improvement (depending on the year) compared with the next closest PRE herbicide treatment. Those with the lowest returns on investment were s-metolachlor combined with halosulfuron, and clomazone and ethalfluralin combined with halosulfuron. Besides providing the highest returns on investment, the PRE application of s-metolachlor with clomazone and ethalfluralin also produced the largest pumpkin fruit for the weed species present. Although growers often look for ways to reduce input costs in NT pumpkin production systems, the proper selection of PRE herbicides that considers the weed species present is clearly an important investment that improves pumpkin yields and revenues.

Growth and Productivity of Black Gram (Vigna mungo L.) as Influenced by Residual Effect of Triafamone Herbicide Applied for Transplanted Rice (Oryza sativa L.)

Background: The major area under black gram are cultivated as rice fallow crop to harness the available soil moisture and other resources without application of any inputs as that of other input intensive crops. Weeds are one of the important biotic factors which affect the growth and yield of black gram. The weeds can be effectively managed in black gram by the herbicide applied in the previous crop viz., transplanted rice. Since, the black gram has quick ground cover, hence initial weed management is very much important. In order to manage the weeds in rice fallow black gram crop evaluation of Triafamone herbicide applied to the transplanted rice crop was carried out in succeeding black gram crop in terms of the growth and yield of black gram. Methods: Field experiments were conducted during Kharif, 2019 (July to August) and Rabi 2019-20 (November to January) at Wetland farm of Tamil Nadu Agricultural University, Coimbatore to study the residual effect of herbicides applied in transplanted rice on succeeding black gram growth and productivity. The experiment was laid out in a randomized complete block design with three replications. The treatments consisted of four doses (30, 40, 50 and 100 g/ha) of new rice herbicide Triafamone 20% SC each as pre emergence and early post emergence, along with check herbicides Pretilachlor 50% EC 750 ml/ha and Pyrazosulfuron ethyl 10% WP 15 ml/ha as early post-emergence along with farmers practice (two hand weedings), weed free and weedy checks. Result: The weed flora of the experimental field consisted of weed complex including grasses, sedges and broad leaved weeds. Among the different dose of herbicides applied, Triafamone 20% SC at 100 g/ha markedly suppressed the weeds growth. There were no phytotoxic effects of herbicides on succeeding black gram. Different doses and time herbicides applied in transplanted rice did not affect the germination of succeeding black gram. Higher weed control efficiency, growth and yield component and yield of black gram were recorded with the Triafamone at 40 g/ha as pre emergence and early post emergence application.

EFFECT OF WEED CONTROL METHODS AND SEEDLING GROWTH STAGESON THE GROWTHOF TRANSPLANTED RICE(Oryza sativa L.) IN DUTSE, JIGAWA STATE

The experiments were carried out in 2020 and 2021 rainy seasons to determine the performance of rice as influenced by seedling age and weed control treatments. The treatments consists of three seedling age (14, 21 and 28 day old seedling) and four weed control methods (hoe weeding, pre emergence application of gramozone (200g/L of paraquat/ha), pre and post emergence of gramozone (200g/L of paraquat/ha) and premix of propanil360g/L + 2,4_D 200g/L) and weedy check). The treatments were laid out in split-plot in a Randomized Complete Block Design (RCBD) and were replicated three times. The results revealed that the plots weeded twice and those treated with pre and post emergence application of gramozone and propanil respectively resulted in taller plant height, large leaf area, and more growth rate than the others weed control methods while weedy check gave the least value. The effect of seedling age on the rice growth revealed that rice transplanted under 14 days old seedling gave tallest plant height, high value of growth rate, relative growth rate and net assimilation value compared to the other methods while 28 days old seedling resulted in the least value of the parameters than others methods. Therefore, it can be concluded that rice farmers in the Sudan savanna zone of Nigeria can adopt pre and post emergence application of gramozone and propanil with transplanting 14 days old seedling since the combination of these treatments gave better weed control and growth of paddy rice.

Field-Evolved ΔG210-ppo2 from Palmer Amaranth Confers Pre-emergence Tolerance to PPO-Inhibitors in Rice and Arabidopsis.

Resistance to protoporphyrinogen IX oxidase (PPO)-inhibitors in Amaranthus palmeri and Amaranthus tuberculatus is mainly contributed by mutations in the PPO enzyme, which renders herbicide molecules ineffective. The deletion of glycine210 (ΔG210) is the most predominant PPO mutation. ΔG210-ppo2 is overexpressed in rice (Oryza sativa c. ‘Nipponbare’) and Arabidopsis thaliana (Col-0). A foliar assay was conducted on transgenic T1 rice plants with 2× dose of fomesafen (780 g ha−1), showing less injury than the non-transgenic (WT) plants. A soil-based assay conducted with T2 rice seeds confirmed tolerance to fomesafen applied pre-emergence. In agar medium, root growth of WT rice seedlings was inhibited >90% at 5 µM fomesafen, while root growth of T2 seedlings was inhibited by 50% at 45 µM fomesafen. The presence and expression of the transgene were confirmed in the T2 rice survivors of soil-applied fomesafen. A soil-based assay was also conducted with transgenic A. thaliana expressing ΔG210-ppo2 which confirmed tolerance to the pre-emergence application of fomesafen and saflufenacil. The expression of A. palmeri ΔG210-ppo2 successfully conferred tolerance to soil-applied fomesafen in rice and Arabidopsis. This mutant also confers cross-tolerance to saflufenacil in Arabidopsis. This trait could be introduced into high-value crops that lack chemical options for weed management.

Effect of Weed Management Practices of Small Onion (Allium cepa var. Aggregatum) Nursery on the Weed Flora, Weed Control Efficiency and Seedling Production

Control of weeds in nursery is necessary for production of healthy and sturdy seedlings. In this regard, field experiments were conducted to study the effect of different weed management practices on weed control efficiency and performance of onion seedling in nursery at two phases. The results from the first experiment revealed that, among the herbicide treatments, lowest weed density and weed dry weight was observed in Pre-emergence (PE) application of oxyfluorfen at 0.250 kg a.i ha-1 followed by PE application of oxyfluorfen at 0.125 kg a.i ha-1. Whereas, the highest weed control efficiency was observed in hand weeded plots followed by pre-emergence application of oxyfluorfen at 0.250 kg a.i ha 1. In the second experiment, lower weed density, weed dry weight and higher weed control efficiency was observed in lay by application oxyfluorfen @ 0.125 kg ha-1 as PE + 2nd application @ 0.0625 kg ha-1 at 20 DAS. Seedling characters viz., higher root length, seedling height, 100 seedling weight and seedling yield was recorded in PE application of oxyfluorfen at 0.125 kg a.i ha-1 and PE application of oxyfluorfen at 0.125 kg a.i ha-1 + oxyfluorfen at 0.0625 kg a.i ha-1 (lay by) at 20 DAS in the first and second experiments respectively.

Preemergence and postemergence spiny amaranth (Amaranthus spinosus) and common lambsquarters (Chenopodium album) control in lettuce on organic soils

AbstractSuccessful weed management, particularly use of chemical control, is very important for commercial lettuce production on organic soils in the Everglades Agricultural Area in south Florida. Field experiments were conducted in 2016 and 2017 to determine the efficacy of herbicides (pronamide, bensulide, imazethapyr, or oxyfluorfen) applied preemergence (PRE) either alone or followed by a postemergence (POST) application of imazethapyr for weed control and lettuce (romaine and iceberg) yield. Preemergence-applied oxyfluorfen (0.56 kg ha−1) resulted in significant lettuce injury, including stand loss, while PRE applications of pronamide (4.44 kg ha−1), bensulide (5.6 and 10.1 kg ha−1), or imazethapyr (0.035 g ha−1) resulted in transient lettuce injury and no significant stand loss. Similarly, PRE-applied pronamide, bensulide, and imazethapyr followed by POST-applied imazethapyr did not result in significant lettuce stand loss or injury. When contrasted as a group, PRE-applied herbicides followed by a POST application of imazethapyr provided better spiny amaranth and common lambsquarters control compared with PRE-applied herbicides or POST-applied imazethapyr-only treatments. Lettuce yield was highest with PRE herbicides followed by POST imazethapyr compared with PRE herbicides or POST-applied imazethapyr-only treatments, indicating a yield benefit of having a PRE followed by POST herbicide weed control program in lettuce grown on organic soils. However, oxyfluorfen is not an option for lettuce on organic soils because of unacceptable stand reduction and crop injury. Whether to apply pronamide, bensulide, or imazethapyr PRE followed by a POST application of imazethapyr for broadleaf weed control in lettuce on organic soils depends on the species present, cost, and ease of application.