Weed Control System Research Articles

Molecular basis for enantioselective herbicide degradation imparted by aryloxyalkanoate dioxygenases in transgenic plants.

The synthetic auxin 2,4-dichlorophenoxyacetic acid (2,4-D) is an active ingredient of thousands of commercial herbicides. Multiple species of bacteria degrade 2,4-D via a pathway initiated by the Fe(II) and α-ketoglutarate (Fe/αKG)-dependent aryloxyalkanoate dioxygenases (AADs). Recently, genes encoding 2 AADs have been deployed commercially in herbicide-tolerant crops. Some AADs can also inactivate chiral phenoxypropionate and aryloxyphenoxypropionate (AOPP) herbicides, albeit with varying substrate enantioselectivities. Certain AAD enzymes, such as AAD-1, have expanded utility in weed control systems by enabling the use of diverse modes of action with a single trait. Here, we report 1) the use of a genomic context-based approach to identify 59 additional members of the AAD class, 2) the biochemical characterization of AAD-2 from Bradyrhizobium diazoefficiens USDA 110 as a catalyst to degrade (S)-stereoisomers of chiral synthetic auxins and AOPP herbicides, 3) spectroscopic data that demonstrate the canonical ferryl complex in the AAD-1 reaction, and 4) crystal structures of representatives of the AAD class. Structures of AAD-1, an (R)-enantiomer substrate-specific enzyme, in complexes with a phenoxypropionate synthetic auxin or with AOPP herbicides and of AAD-2, which has the opposite (S)-enantiomeric substrate specificity, reveal the structural basis for stereoselectivity and provide insights into a common catalytic mechanism.

Sugarbeet tolerance when dimethenamid-P follows soil-applied ethofumesate and S-metolachlor

AbstractSugarbeet growers only recently have combined ethofumesate, S-metolachlor, and dimethenamid-P in a weed control system for waterhemp control. Sugarbeet plant density, visible stature reduction, root yield, percent sucrose content, and recoverable sucrose were measured in field experiments at five environments between 2014 and 2016. Sugarbeet stand density and stature reduction occurred in some but not all environments. Stand density was reduced with PRE application of S-metolachlor at 1.60 kg ai ha–1 and S-metolachlor at 0.80 kg ha–1 + ethofumesate at 1.68 kg ai ha–1 alone or followed by POST applications of dimethenamid-P at 0.95 kg ai ha–1. Sugarbeet visible stature was reduced when dimethenamid-P followed PRE treatments. Stature reduction was greatest with ethofumesate at 1.68 or 4.37 kg ha–1 PRE and S-metolachlor at 0.80 kg ha–1 + ethofumesate at 1.68 kg ha–1 PRE followed by dimethenamid-P at 0.95 kg ha–1 POST. Stature reduction ranged from 0 to 32% 10 d after treatment (DAT), but sugarbeet recovered quickly and visible injury was negligible 23 DAT. Although root yield and recoverable sucrose were similar across herbicide treatments and environments, we caution against the use of S-metolachlor at 0.80 kg ha–1 + ethofumesate at 1.68 kg ai ha–1 PRE followed by dimethenamid-P at 0.95 kg ha–1 in sugarbeet.

The influence of non-chemical weed control methods on sugar beet productivity and quality parameters

A long-term stationary field experiment was carried out at the Experimental Station of Aleksandras Stulginskis University (Vytautas Magnus University Agriculture Academy since 2019) in 2017. The following sustainable weed control methods were examined: 1) inter-row loosening (control treatment); 2) inter-row cutting and mulching with weeds; 3) inter-row cutting and mulching with Persian clover; 4) inter-row cutting and mulching with white mustards; 5) interrow cutting and mulching with spring barley. The alternatives to weed control often reduced the yields of sugar beet roots significantly, however, when mulching with white mustard the decrease in fertility was not essential. Non-chemical weed control measures in most cases had an insignificant effect on the parameters of sugar beet quality – the content of Na, K and alpha-amino N. The most significant sugar content (16.34 and 16.26%) was found in sugar beets, which were grown applying interrow mulch of spring barley and weed (P < 0.05). Although insignificant, but the largest index of sugar beet leaf area was found in the experimental plots, where inter-row cutting out and mulching with white mustard were applied. Comparing non-chemical weed control systems, the highest amount of white (crystalline) sugar (4.96 ha–1) was derived from the sugar beet that was grown using white mustard mulch.

Socioecological resilience of typical citrus fruit agroecosystems

This paper, as a tool for analysis, considered the capacity of the interaction that open systems have against the occurrence of disturbances so that they can continue to function with minimal losses of energy, called resilience, an emerging characteristic of agroecosystems. To establish a method to measure this characteristic, ten variables were evaluated, including seven cultural variables: level of schooling, land tenure type, saving capacity, social organizational identity, farm infrastructure, weed control and production system; and three ecosystem variables: water resource availability, phytosanitary management and Main Agroecological Structure (MAS) in typical citrus fruit agroecosystems. These were methodologically grouped into six recommended domains: groups of farms and citrus growers with similar ecosystem and cultural conditions that have been characterized and typified in a previous study. In each of these groups, three farm types were selected for a total of 18 production units (department of Meta, Colombia). To determine the difference between the variables, Chi-square tests were applied (using the Pearson and Fisher statistics). Network analysis was applied to determine the relationship between the variables. The resilience was not significantly correlated with level of schooling, farm infrastructure or MAS. The relationship between the resilience and cultural variables presented a high significance, whereas the ecosystem variables showed a low statistical significance.

The effect of cotton growth stage on response to a sublethal concentration of 2,4-D

AbstractRecent commercialization of auxin herbicide–based weed control systems has led to increased off-target exposure of susceptible cotton cultivars to auxin herbicides. Off-target deposition of dilute concentrations of auxin herbicides can occur on cotton at any stage of growth. Field experiments were conducted at two locations in Mississippi from 2014 to 2016 to assess the response of cotton at various growth stages after exposure to a sublethal 2,4-D concentration of 8.3 g ae ha−1. Herbicide applications occurred weekly from 0 to 14 weeks after emergence (WAE). Cotton exposure to 2,4-D at 2 to 9 WAE resulted in up to 64% visible injury, whereas 2,4-D exposure 5 to 6 WAE resulted in machine-harvested yield reductions of 18% to 21%. Cotton maturity was delayed after exposure 2 to 10 WAE, and height was increased from exposure 6 to 9 WAE due to decreased fruit set after exposure. Total hand-harvested yield was reduced from 2,4-D exposure 3, 5 to 8, and 13 WAE. Growth stage at time of exposure influenced the distribution of yield by node and position. Yield on lower and inner fruiting sites generally decreased from exposure, and yield partitioned to vegetative or aborted positions and upper fruiting sites increased. Reductions in gin turnout, micronaire, fiber length, fiber-length uniformity, and fiber elongation were observed after exposure at certain growth stages, but the overall effects on fiber properties were small. These results indicate that cotton is most sensitive to low concentrations of 2,4-D during late vegetative and squaring growth stages.

Design, development, and evaluation of a target oriented weed control system using machine vision

The objective of the study was to develop and test an automatic machine vision-based spraying robot for the detection, tracking, and spraying of artificial weeds by using LabVIEW programming language. The greenness method was used to distinguish green objects in the image. A time-controlled spray nozzle was run according to the presence of an artificial weed and its coordinates. A mobile test bench was built and the spraying system with a webcam was operated at speeds of 0.42, 0.54, 0.66, 0.78, and 0.90 km h-1, so as to be able to see the performance of the system. The amount of deposits on the ground in the spray pattern was evaluated on the test area and used in comparisons for site specific and broadcast spraying methods. A spraying solution containing brilliant sulpho-flavin (BSF) tracer (0.4 g L-1) and filter papers were used to compare the deposition of spray pattern achieved on the ground with both methods. According to the results, site-specific spraying application saved on average 89.48%, 79.98%, and 73.93% application volumes for 500 ms, 1000 ms, and 1500 ms spraying durations, respectively, at all spraying speeds is compared to broadcast spraying application. As one would expect, deposits on the filter papers decreased with increasing spraying speed. In addition, operating the system with 1000 ms nozzle controlled site specific spraying at different speeds did not cause a significant difference in the amount of deposits in the spray pattern and spraying accuracy as compared to the broadcast spraying method.

Establishment of a plant phosphorus utilization and weed control system based on phosphite and its dehydrogenase

Nowadays, available phosphorus (P) deficiency in soil and weed resistance to herbicides have emerged as two severe limiting factors for sustainable agriculture. Therefore, it is of urgent needs to improve plant absorption/utilization ability of the soil P, seek phosphate (Pi)-alternative P fertilizers, and develop new forms of weed control systems. Phosphite (Phi), as a P resource of relatively high amount only less than Pi in Earth, can be converted to utilizable Pi uniquely in some bacterial species by oxidization via its specific dehydrogenase (PTDH), but inhibits plant growth and development. This implies that Phi might rather become a suitable P fertilizer for plants if introducing a PTDH detoxifier from bacteria. Herein, we created the transgenic tobaccos harboring a Pseudomonas PTDH gene (PsPtx) amplified from the soil metagenome previously. RT-PCR showed that the exotic PsPtx gene could express similarly in root, stem and leaf tissues of all transgenic lines. PsPtx transgenic tobaccos could utilize Phi by oxidization as the sole Pi supply, and also outperformed wild-type tobacco with a remarkably dominant growth under Phi stress conditions. Moreover, the PsPtx gene was preliminarily evaluated with a notable quality as a potential candidate of the selection marker in plant genetic transformation. Conclusively, PsPtx and its encoded phosphite dehydrogenase might be applicable for developing a dual system of plant phosphorus utilization and weed control using Phi as P fertilizer and herbicide, and provide an effectual solution to some obstacles in the current crop transgenic studies.

Dynamics and distribution of weed species in weed associations

Dynamics of weed density with a natural background of weeds in agrophytocenoses of sainfoin (Onobrychis sativa L.), birdsfoot trefoil (Lotus corniculatus L.) and alfalfa (Medicago sativa L.), pure grown (100%) and in mixtures with cocksfoot (Dactylis glomerata L.) (50:50%) and sown under a cover of pea (Pisum sativum L.) were tested in field trial in the Institute of Forage Crops, Pleven, Bulgaria. It was found that the weed infestance and species composition changed depending on the type of еdificator. The species composition in weed associations was the highest in pure grown Lotus corniculatus L. In mixtures of Onobrychis sativa L. + Dactylis glomerata L. the highest weed infestance was recorded, and the lowest in Onobrychis sativa L. under cover of Pisum sativum L. Weed infestance in mixtures was lower as compared to pure grown swards, except Medicago sativa L. + Dactylisglomerata L. For the specific environment of study the highest part for annual dicotyledonous weed species (from 0.0 to 49.5%), followed by perennial dicotyledonous (from 3.7 to 58.2%) was obsereved. There was a strong variation in the percentage in agrophytocenoses of Convolvulus arvensis L. (from 0.0 to 11.4%), Sonchus arvensis L. (from 0.0 to 19.0%) and Erigeron canadensis L. (from 0.0 to 47.8%), whereas Matricaria recutita L. varied within narrow range (0.0 to 3.7%). The dependance allows to be used for developing more effective weed control systems in the studied forage crops and mixtures.

Constructive-technological diagram of the rotary–string cultivator and the definition of its main parameters

Organizing technological processes in accordance with adopted system of agriculture, producers of agricultural products tend to get maximum possible yield with minimizing costs and increasing the level of soil fertility. A fallow system is one of effective systems of soil processing for accumulation of nutrients and moisture, as well as weed control. Fallow cultivation of soil is used when using this system for weed control. First cultivation is carried out with help of fallow or continuous cultivators, which have low productivity and high energy intensity. To eliminate these shortcomings, authors proposed a structural and technological scheme of a rotor-lug cultivator, the main element of which is rotor-string working bodies on flexible shaft. Tillage rotary-string work by hauling leads to propelling-rotational effects. There were obtained analytical dependences for determining speed of string required for cutting stem of weeds under different physical-mechanical parameters of stem and soil, as well as technological indicators of a cultivator’ operation. The authors obtained expressions for determining the radius of string installation from axis of rotation, angle of section installation to the direction of motion of energy means, as well as the number of strings required for guaranteed cutting of weeds deeper than the point of growth.

Integration and potential nitrogen contributions of green manure inter-row legumes in coppiced tree cropping systems

Legumes play a key role in maintaining soil fertility in pasture systems and when used as a rotation crop or relay crop in annual cropping systems. Little is known about the potential to integrate green manure legumes into coppiced or ratooned perennial crop systems. We trialled the cultivation and green manuring of four annual legume species in the inter-row of coppiced tea tree (Melaleuca alternifolia) and assessed potential nitrogen (N) contributions using 15N natural abundance methodology. The yield and N uptake of tea tree crops with legumes was compared with tea tree crops amended with 5 t ha−1 (wet) poultry litter as per standard practice. At two field sites where warm-season legumes were sown in spring into coppiced tea tree stands, soybean (Glycine max) had a higher % N derived from the atmosphere (%Ndfa) than mung beans (Vigna radiata) (82 vs 68% at Casino and 65 vs 56% at Tweed Heads) and contributed more fixed N (shoots + roots) to the soil than mung bean at both sites (91 vs 24 kg fixed N ha−1 at Casino and 61 vs 33 kg fixed N ha−1 at Tweed Heads). Where cool-season legumes were sown into tea tree stands coppiced in winter, faba bean (Vicia faba) had a higher %Ndfa than chickpea (Cicer arietinum) at Rappville (88 vs 68%). Chickpea fixed less than 10 kg N ha−1 at Rappville, while faba been fixed 36 kg N ha−1 at Rappville and 92 kg N ha−1 at Leeville. At one site (Casino) tea tree yields in the legume plots were significantly (10–15%) lower than the poultry litter plots. The nutrient content of tea tree did not differ among treatments for any measured micro- or macronutrients, and the cause of the yield loss remains unknown. Ultimately, the highest fixed-N contributions of faba bean (92 kg fixed-N ha−1 at Leeville) and soybean (91 kg fixed-N ha−1 at Casino) equated to more than the amount of N in harvested shoot of a low yielding tea tree crop (67 kg N ha−1 at Leeville) and around 2/3 the N accumulated in harvested shoots of a high yielding tea tree crop (129 kg N ha−1 at Casino). Green manure legume crops have the potential to reduce the need for external N fertiliser inputs in coppiced tree crops, but further refinement is needed to integrate legumes into current weed control systems, optimise the timing of N release from decaying legume residues, and to minimise any competition between legumes and the tree crops for water, light or nutrients.

Effect of Growth Stage on Cotton Response to a Sublethal Concentration of Dicamba

AbstractThe introduction of auxin herbicide weed control systems has led to increased occurrence of crop injury in susceptible soybeans and cotton. Off-target exposure to sublethal concentrations of dicamba can occur at varying growth stages, which may affect crop response. Field experiments were conducted in Mississippi in 2014, 2015, and 2016 to characterize cotton response to a sublethal concentration of dicamba equivalent to 1/16X the labeled rate. Weekly applications of dicamba at 35 g ae ha−1were made to separate sets of replicated plots immediately following planting until 14 wk after emergence (WAE). Exposure to dicamba from 1 to 9 WAE resulted in up to 32% visible injury, and exposure from 7 to 10 WAE delayed crop maturity. Exposure from 8 to 10 and 13 WAE led to increased cotton height, while an 18% reduction in machine-harvested yield resulted from exposure at 6 WAE. Cotton exposure at 3 to 9 WAE reduced the seed cotton weight partitioned to position 1 fruiting sites, while exposure at 3 to 6 WAE also reduced yield in position 2 fruiting sites. Exposure at 2, 3, and 5 to 7 WAE increased the percent of yield partitioned to vegetative branches. An increase in percent of yield partitioned to plants with aborted terminals occurred following exposure from 3 to 7 WAE and corresponded with reciprocal decreases in yield partitioned to positional fruiting sites. Minimal effects were observed on fiber quality, except for decreases in fiber length uniformity resulting from exposure at 9 and 10 WAE.

Evaluation of weed control system including pre-plant tillage and pre-emergence herbicides, for Italian ryegrass in wheat fields, in Higashimikawa area, Aichi

Evaluation of weed control system including pre-plant tillage and pre-emergence herbicides, for Italian ryegrass in wheat fields, in Higashimikawa area, Aichi

Control of Glyphosate-Resistant Common waterhemp (Amaranthus rudis) in Three New Herbicide-Resistant Soybean Varieties in Ontario

Glyphosate-resistant (GR) common waterhemp (CW) is a localized weed in Ontario and one of the most problematic weeds in the US Corn Belt. First confirmed in Ontario in 2014, GR CW has now been confirmed in forty fields in three counties in Ontario as of 2015. Historically, the primary POST herbicides used for the control of CW in soybean were glyphosate, acifluorfen and fomesafen, but resistance to all three has been confirmed in many US states. Research was conducted in 2015 and 2016 to determine the control of GR CW with some of the new herbicide-resistant soybean technologies including glufosinate (LibertyLink), 2,4-D and glyphosate (Enlist), and isoxaflutole, mesotrione, and glufosinate (HPPD-resistant). Glyphosate-resistant CW was controlled (≥90%) all season with a two-pass weed control system across all herbicide-resistant soybean technologies evaluated. The two-pass weed control system in this research is defined as a PRE herbicide followed by a POST herbicide. At 12 WAA, the two-pass programs in LibertyLink, Enlist, and HPPD-resistant systems controlled GR CW up to 98, 98, and 92%, respectively, and reduced GR CW densities to 0 to 2% of the weedy control at 4 WAA. The two-pass programs provided greater GR CW control than PRE or POST herbicides alone. This study found that the use of two-pass weed control programs in glufosinate-resistant, glyphosate DMA/2,4-D choline-resistant and HPPD-resistant soybean can provide excellent control of GR CW, and can be valuable tools to reduce the selection intensity for herbicide-resistant weeds. Through the rotational use of different technologies, growers may be able to better manage their weed populations in reducing the risk of resistance when compared to the use of one herbicide repeatedly.

Image-based recognition framework for robotic weed control systems

In this paper, we introduce a novel and efficient image-based weed recognition system for the weed control problem of Broad-leaved Dock (Rumex obtusifolius L.). Our proposed weed recognition system is developed using a framework, that allows the examination of the affects for various image resolutions in detection and recognition accuracy. Moreover, it includes state-of-the-art object/image categorization processes such as feature detection and extraction, codebook learning, feature encoding, image representation and classification. The efficiency of those processes have been improved and optimized by introducing methodologies, techniques and system parameters specially tailored for the goal of weed recognition. Through an exhaustive optimization process, which is presented as our experimental evaluation, we conclude to a weed recognition system that uses an image input resolution of 200 ×150, SURF features over dense feature extraction, an optimized Gaussian Mixture Model based codebook combined with Fisher encoding, using a two level image representation. The resulting image representation vectors are classified using a linear classifier. This system is experimentally shown to yield state-of-the-art recognition accuracy of 89.09% in the examined dataset. Our proposed system is also experimentally shown to comply with the specifications of the examined applications since it provides low false-positive results of 4.38%. As a result, the proposed framework can be efficiently used in weed control robots for precision farming applications.

흑미 무논점파 재배방법에 따른 수량 및 품질특성과 잡초방제체계

흑미 무논점파 재배방법에 따른 수량 및 품질특성과 잡초방제체계

Biokinetic Analysis and Metabolic Fate of 2,4-D in 2,4-D-Resistant Soybean (Glycine max).

The Enlist weed control system allows the use of 2,4-D in soybean but slight necrosis in treated leaves may be observed in the field. The objectives of this research were to measure and compare uptake, translocation, and metabolism of 2,4-D in Enlist (E, resistant) and non-AAD-12 transformed (NT, sensitive) soybeans. The adjuvant from the Enlist Duo herbicide formulation (ADJ) increased 2,4-D uptake (36%) and displayed the fastest rate of uptake (U50= 0.2 h) among treatments. E soybean demonstrated a faster rate of 2,4-D metabolism (M50= 0.2 h) compared to NT soybean, but glyphosate did not affect 2,4-D metabolism. Metabolites of 2,4-D in E soybean were qualitatively different than NT. Applying 2,4-D-ethylhexyl ester instead of 2,4-D choline (a quaternary ammonium salt) eliminated visual injury to E soybean, likely due to the time required for initial de-esterification and bioactivation. Excessive 2,4-D acid concentrations in E soybean resulting from ADJ-increased uptake may significantly contribute to foliar injury.

Selectivity of foramsulfuron + thiencarbazone‐methyl and classic herbicides in sensitive and non‐sensitive sugar beet genotypes

SummaryA new herbicide for sugar beet cultivation using the ALS‐inhibiting active ingredients foramsulfuron and thiencarbazone‐methyl is under approval in the EU member states. Sugar beet genotypes that are non‐sensitive to this herbicide are currently under development. Selectivity of the ALS‐inhibiting herbicide and yield response of the non‐sensitive genotypes might be relevant to meet the requirements for variety registration. To evaluate these issues, six field trials were conducted in Germany in 2013 and 2014. Classic herbicides and the ALS‐inhibitor herbicide were applied in dosages of up to fourfold the authorised (or applied for) application rates. The ALS‐inhibitor herbicide did not cause any significant phytotoxicity and had no effect on leaf area index at a single, double or fourfold dosage. By contrast, classic herbicides had significant negative effects at the single dosage. At fourfold dosage, they caused 41% phytotoxicity and reduced leaf area index by 35%. The relative yield difference between ALS‐inhibitor and classic herbicide treatments was 8.6% and 17.4% of white sugar yield at double and fourfold dosage respectively. The ALS‐inhibitor herbicide thus showed higher selectivity than the classic herbicides. In the registration process, the resulting yield advantage could balance a possible yield penalty of non‐sensitive genotypes. The introduction of a new system for weed control could improve application flexibility and control of troublesome weeds in sugar beet.

Cover Crop and Postemergence Herbicide Integration for Palmer amaranth Control in Cotton

Field experiments were conducted to evaluate the integration of cover crops and POST herbicides to control glyphosate-resistant Palmer amaranth in cotton. The winter-annual grasses accumulated the greatest amount of biomass and provided the most Palmer amaranth control. The estimates for the logistic regression would indicate that 1540 kg ha−1would delay Palmer amaranth emerging and growing to 10 cm by an estimated 16.5 days. The Palmer amaranth that emerged in the cereal rye and wheat cover crop treatments took a longer time to reach 10 cm compared to the hairy vetch and crimson clover treatments. POST herbicides were needed for adequate control of Palmer amaranth. The glufosinate-based weed control system provided greater control (75% vs 31%) of Palmer amaranth than did the glyphosate system. These results indicate that a POST only herbicide weed management system did not provide sufficient control of Palmer amaranth, even when used in conjunction with cover crops that produced a moderate level of biomass. Therefore, future recommendations for GR Palmer amaranth control will include integrating cover crops with PRE herbicides, overlaying residual herbicides in-season, timely POST herbicide applications, and hand weeding in order to achieve season-long control of this pest.

40. 畑作物の連輪作と雑草発生との関係 : 続報(年次講演会要旨)

40. 畑作物の連輪作と雑草発生との関係 : 続報(年次講演会要旨)

벼 담수직파 논 잡초방제 체계에 따른 올방개 방제 특성

벼 담수직파 재배시 제초제 사용에 따른 잡초발생 생태를 구명하고, 합리적인 잡초방제 체계를 확립하고자 연구한 결과는 다음과 같다. 벼 종자 파종 후 12일에 설포닐우레아계 혼합제초제(azimsulfuron + carfentrazone-ethyl + pyriminobac-methyl) 처리는 피 등 일년생잡초의 방제효과는 높았으나, 올방개의 방제효과는 낮았다. 그러나, 설포닐우레아계 혼합제초제 초중기처리 후 20일에 설포닐우레아계 혼합제초제(pyrazosulfuron-ethyl + thiobencarb)의 체계처리는 올방개의 방제효과가 높고, 새로운 괴경의 형성량은 적었으나, 구 괴경의 휴면율은 높았다. 또한 설포닐우레아계 혼합제초제의 초중기처리와 파종 후 55일에 bentazone 액제의 체계처리는 올방개의 방제효과가 높고, 새로운 괴경의 형성량도 적었으며, 휴면 괴경도 적었다. This study was conducted to investigate the ecology of weed occurrence and to establish an economical paddy field weed control system for direct-seeded rice on water. The main problem weed among annual and perennial weeds was Eleocharis kuroguwai. The control effect of E. kuroguwai was low by the application of azimsulfuron + carfentrazone-ethyl + pyriminobac-methyl at the early stages of rice in directly seeded paddy fields, but most annual weeds including Echinochloa crus-galli were controlled. Also, the additional application of pyrazosulfuron-ethyl + thiobencarb GR at 20 days after first treatment or of bentazone SL at 43 days after the first treatment effectively controlled E. kuroguwai. Tuber formation of E. kuroguwai was inhibited by the additional application of pyrazosulfuron-ethyl + thiobencarb by 84%, but the dormancy rate of old tubers of E. kuroguwai under the soil was higher than that of E. kuroguwai tubers following single application of azimsulfuron + carfentrazone-ethyl + pyriminobac-methyl at the early stages of rice. Tuber formation was inhibited by the additional application of bentazone by approximately 87%, and the old tuber dormancy rate was low in the bentazone treatment. High amounts of old dormant tubers of E. kuroguwai were found in the weedy plots.