Rice Weeds Research Articles

Drone-based herbicide application for energy saving, higher weed control and economics in direct-seeded rice (Oryza sativa)

A field experiment was conducted at Tamil Nadu Agricultural University, Coimbatore during kharif (rainy) and rabi (winter) seasons of 2022 and 2023 to evaluate the efficiency, energy and economics of drone-based herbicide application in direct-seeded rice (Oryza sativa L.). The study was carried out with application of pre-emergence, early post-emergence and post-emergence herbicides using drone and knapsack sprayer to assess the weed control efficiency. Treatments included pretilachlor followed by (fb) application of post-emergence herbicides, such as bispyribacsodium (Na), fenoxyprop ethyl + carfentrazone ethyl and early post-emergence herbicides, such as bispyribac-Na, fenoxyprop ethyl + carfentrazone ethyl, bispyribac-Na fb post-emergence of fenoxyprop ethyl + carfentrazone ethyl, weed-free check and unweeded check. Application of pretilachlor fb bispyribac-Na using knapsack sprayer reduced weed density from 83 to 87% and weed dry weight from 81 to 83% over unweeded plot. Moreover, it was found on par with drone application of same herbicides in both seasons. Pretilachlor fb bispyribac-Na application through knapsack sprayer and drone produced higher grain yield and it was comparable with weed-free plot. Higher net return, benefit: cost ratio (2.27 and 2.09), energy-use efficiency (10.86 and 9.55 MJ) and energy productivity (0.81 and 0.71 kg/MJ) were noticed with drone application of pretilachlor fb bispyribac-Na in both the seasons. From the experiment, drone application of pretilachlor fb bispyribac-Na is found as an effective strategy to manage weeds in direct-seeded rice and more advantageous in terms of energy-use and profitability.

Effect of Different Weed Management Practices on Nutrient Uptake by Weeds and Crop Yield of Organic Basmati Rice (Oryza sativa L.)

An field experiment was conducted during Kharif season of 2021at the Organic Farming Research Centre, Chatha, SKUAST- J to evaluate the effect of different weed management practices on nutrient uptake and yield in organic basmati rice production. The experiment was conducted in Randomized Block Design with 11 treatments which were replicated thrice. The highest nitrogen (29.66 kg/ha), phosphorus (16.22 kg/ha) and potassium (32.66 kg/ha) uptake by weeds were recorded in weedy check. Amongst organic weed management treatments, application of vinegar @ 10 % at 5 DBT + hand weeding at 30 DAT which was though statistically at par with recommended practice of two hand weeding at 20 and 40 DAT recorded significantly lowest nitrogen (2.31 kg/ha), phosphorus (1.21 kg/ha) and potassium (2.44 kg/ha) uptake by weeds followed by the application of vinegar @ 5 % at 5 DBT + hand weeding at 30 DAT and application of rice bran @ 2.5 t/ha (extract at 1:3 wt./vol. basis) at 5 DBT + hand weeding at 30 DAT than weedy check and other organic weed management treatments in comparison. However, maximum grain and straw yield was recorded with the application of vinegar @ 10% at 5 DBT fb one hand weeding at 30 DAT to the tune of 31.17 q/ha and 54.27 q/ha, respectively. Thus, it may be concluded that the application of vinegar @ 10 % at 5 DBT fb one hand weeding at 30 DAT may be recommended as economical viable option in organic basmati rice crop.

EXPLORING MORPHOLOGICAL TRAITS VARIATION IN CHENOPODIUM MURALE: A COMPREHENSIVE MULTIVARIATE ANALYSIS

Chenopodium murale, a significant weed in wheat, maize, rice, sugarcane, and cotton fields, poses a substantial threat to crop plants due to its competitive nature for water, minerals, and nutrients, leading to significant yield losses. To address this issue, a prescribed study was conducted to assess the morphological traits of Chenopodium murale under three different environmental locations. The results revealed a positive and significant correlation among several study traits: height, dry weight, fresh weight, inflorescence fresh weight, leaf area, leaf length, leaf width, and root length. Notably, plant leaf width emerged as the most influential trait contributing to the plant's height. Furthermore, the study identified location three as an exceptionally favorable environment for the robust growth and development of Chenopodium murale plants. To mitigate potential yield losses in crop plants, the study recommends the timely removal or control of Chenopodium murale, emphasizing the importance of managing its population effectively.

Development of Magnetic Lateral Flow and Direct Competitive Immunoassays for Sensitive and Specific Detection of Halosulfuron-Methyl Using a Novel Hapten and Monoclonal Antibody.

Halosulfuron-methyl (HM) is widely used for the removal of noxious weeds in corn, sugarcane, wheat, rice, and tomato fields. Despite its high efficiency and low toxicity, drift to nontarget crops and leaching of its metabolites to groundwater pose potential risks. Considering the instability of HM, the pyrazole sulfonamide of HM was used to generate a hapten and antigen to raise a high-quality monoclonal antibody (Mab, designated 1A91H11) against HM. A direct competitive immunoassay (dcELISA) using Mab 1A91H11 achieved a half-maximal inhibitory concentration (IC50) of 1.5 × 10-3 mg/kg and a linear range of 0.7 × 10-3 mg/kg-10.7 × 10-3 mg/kg, which was 10 times more sensitive than a comparable indirect competitive ELISA (icELISA) and more simple to operate. A spiking recovery experiment performed in tomato and maize matrices with 0.01, 0.05, and 0.1 mg/kg HM had average recoveries within 78.9-87.9% and 103.0-107.4% and coefficients of variation from 1.1-6.8% and 2.7-6.4% in tomato and maize, respectively. In addition, a magnetic lateral flow immunoassay (MLFIA) was developed for quantitative detection of low concentrations of HM in paddy water. Compared with dcELISA, the MLFIA exhibited 3.3- to 50-fold higher sensitivity (IC50 0.21 × 10-3 mg/kg). The average recovery and RSD of the developed MLFIA ranged from 81.5 to 92.5% and 5.4 to 9.7%. The results of this study demonstrated that the developed dcELISA and MLFIA are suitable for rapid detection of HM residues in tomato and maize matrices and paddy water, respectively, with acceptable accuracy and precision.

Estimation of the economic threshold of Leptochloa chinensis (Chinese sprangletop) in direct-seeded fine grain rice (Oryza sativa)

: Leptochloa chinensis (L.) Nees (Chinese sprangletop) is a weed that is becoming a serious threat in upland and lowland rice. A field study was conducted at the Agronomic Research Farm, University of Sargodha, Punjab, Pakistan, during the summer seasons of 2018 and 2019 to evaluate the effect of L. chinensis density on the yield of direct-seeded fine rice. Treatments comprised of L. chinensis densities of 0, 5, 10, 15, 20 and 25 plants m-2, and the experiment was laid out in a randomized complete block design with four replications of each treatment. The results suggest that the presence of L. chinensis significantly hampered the grain yield of direct-seeded rice. Weed infestation caused 63% and 69% yield losses where 25 L. chinensis plants m-2 were sustained in 2018 and 2019, respectively. Yield reduction was due to the reduction in 1000-grain weight (22.9 and 29.1%), number of tillers m-2 (65.8 and 60.0%), and number of grains panicle-1 (53.3 and 60%) in 2018 and 2019, respectively. The highest weed infestation (25 plants m-2) produced the highest weed dry biomass (687 and 669 g m-2), N uptake (19.3 and 19.3 kg ha-1), P uptake (1.92 and 2.32 kg ha-1), and K uptake (20.53 and 20.27 kg ha-1) in 2018 and 2019, respectively. The lowest weed infestation (5 plants m-2) produced minimum weed dry biomass (47 and 85 g m-2), N uptake (1.6 and 2.9), P uptake (0.3 and 0.5), and K uptake (1.7 and 30 kg ha-1) in 2018 and 2019, respectively. The economic threshold of L. chinensis as estimated to cause 6.73% and 6.08% yield loss by the prediction model was 1.70 and 1.73 plants m-2 during 2018 and 2019, respectively. It can be concluded that L. chinensis is a serious weed in direct-seeded rice and it should be controlled when its density reaches 1.70-1.73 plants m-2 to avoid significant yield losses.

MSFCA-Net: A Multi-Scale Feature Convolutional Attention Network for Segmenting Crops and Weeds in the Field

Weed control has always been one of the most important issues in agriculture. The research based on deep learning methods for weed identification and segmentation in the field provides necessary conditions for intelligent point-to-point spraying and intelligent weeding. However, due to limited and difficult-to-obtain agricultural weed datasets, complex changes in field lighting intensity, mutual occlusion between crops and weeds, and uneven size and quantity of crops and weeds, the existing weed segmentation methods are unable to perform effectively. In order to address these issues in weed segmentation, this study proposes a multi-scale convolutional attention network for crop and weed segmentation. In this work, we designed a multi-scale feature convolutional attention network for segmenting crops and weeds in the field called MSFCA-Net using various sizes of strip convolutions. A hybrid loss designed based on the Dice loss and focal loss is used to enhance the model’s sensitivity towards different classes and improve the model’s ability to learn from hard samples, thereby enhancing the segmentation performance of crops and weeds. The proposed method is trained and tested on soybean, sugar beet, carrot, and rice weed datasets. Comparisons with popular semantic segmentation methods show that the proposed MSFCA-Net has higher mean intersection over union (MIoU) on these datasets, with values of 92.64%, 89.58%, 79.34%, and 78.12%, respectively. The results show that under the same experimental conditions and parameter configurations, the proposed method outperforms other methods and has strong robustness and generalization ability.

Target and nontarget mechanisms of AHAS inhibitor cross-resistance patterns in Cyperus difformis

Weed resistance to acetohydroxyacid synthase (AHAS) inhibiting herbicides has been a critical issue for rice growers worldwide since the early 1990's. In California, resistance to bensulfuron-methyl was first detected in Cyperus difformis in 1993. Since then, populations of most major weeds of rice in California have been reported to show resistance to at least one AHAS inhibitor. We sought to describe the magnitude and mechanisms of AHAS inhibitor cross-resistance in California populations of C. difformis. Sixty-two populations were collected and screened for cross-resistance to bensulfuron-methyl (BEN), halosulfuron-methyl (HAL), bispyribac‑sodium (BIS), and penoxsulam (PEN), revealing six major patterns of cross-resistance. Representative C. difformis populations from each cross-resistance pattern were then subjected to dose-response, cytochrome P450 inhibition, AHAS gene sequencing, and metabolic studies with the same herbicides as in the screening. Dose-response confirmed the detected resistances in the representative populations, and suggested that the majority of observed resistance was dose-dependent. Cytochrome P450 inhibition via malathion revealed evidence of increased metabolic activity in resistant populations to BEN, BIS, and PEN. AHAS gene sequencing revealed amino acid substitutions in five of six populations: R3 (Pro197-Ser), R4 (Pro97-His), R10 (Asp376), R41 (Ala122-Asn), and R18 (Trp574-Leu). Metabolic studies confirmed evidence of increased activity of cytochrome P450s in all populations. Metabolic BEN and HAL analysis did not yield similar results to malathion inhibition, suggesting different P450's or other pathways. Taken together, the results of the studies confirm the complexity of AHAS inhibitor cross-resistance in C. difformis, and the presence of both target-site and metabolic resistance in most of the representative populations underscores the importance of proper herbicide selection, rotation, and scouting in fields.

Competitiveness of Bensulfuron-Methyl-Susceptible and -Resistant Biotypes of Ammannia auriculata Willd. in Direct-Seeded Rice

Ammannia auriculata Willd. (eared redstem) has become one of the most troublesome weeds in paddy rice in China. Resistance to bensulfuron-methyl (BSM) has spread extensively in this species. Greenhouse and field experiments were conducted to determine how the eared redstem biotype and density affect competition against rice. In the greenhouse experiment, five treatments were tested: a BSM-susceptible biotype at low density (58 plants m−2, SL), a BSM-susceptible biotype at high density (288 plants m−2, SH), a BSM-resistant biotype at low density (RL), a BSM-resistant biotype at high density (RH), and a control without eared redstem (CK). Eared redstem grew slowly until 15 days after sowing (DAS); however, growth accelerated after 20 DAS, and the eared redstem plants were taller than the rice from 55 DAS on. The SH and RH treatments were associated with greater intraspecific competition: eared redstem plants in the SH and RH treatments had fewer branches, fewer capsules, and less shoot dry weight per individual plant relative to the SL and RL treatments. The SH and RH treatments also caused greater reductions in the rice yield. The dry weight of rice at 141 DAS was reduced by 73% in the SL treatment, 98% in the SH treatment, 51% in the RL treatment, and 82% in the RH treatment, all relative to the CK. At 141 DAS, BSM-resistant plants were smaller than BSM-susceptible plants, suggesting a fitness cost of herbicide resistance in the absence of a herbicide. In the field study, eared redstem densities as low as 5 plants m−2 reduced the rice yield by 22%. A density of 50 eared redstem plants m−2 reduced the rice yield by 70%. Overall, these findings demonstrate that eared redstem is a highly aggressive weed species and threatens the rice yield even at a low density. However, the findings also demonstrate that BSM-resistant populations are less competitive. There is an urgent need to develop integrated management programs for this aggressive weed, which may include tactics to shift competitive dynamics in favor of rice. Additionally, this research provides the theoretical basis for the damage level, resistance risk evaluation, and management strategy of eared redstem in rice cropping systems.

Herbicide Resistance Management in Rice: Annual Field Survey of California Rice Weeds Helps Establish a Weed Management Decision Framework

The article presents an annual field survey by the University of California as a manner of herbicide resistance management for California rice growers. Submitted weed seed samples are tested against registered herbicides which achieved no control that field season. All labelled herbicide modes of action for each specific weed species were tested and applied according to their respective labels. Analyses of these experiments and survey data from 2015 to 2021 provide an active weed management decision-making framework for growers and a comprehensive overview of herbicide weed management in California rice.

Effect of different establishment methods and weed management strategies in rice (Oryza sativa) under Cauvery delta zone of Tamil Nadu

Higher demand, cost of labour and low availability of water have forced the farmers to look for an alternative method of rice cultivation as a substitute to the existing conventional method of transplanting. Direct method of rice cultivation is better alternative over transplanting method. This is not only laboursaving method, but also results in significant water saving method in rice cultivation. However, the direct method of rice cultivation confronts with severe weed infestation in initial stage of crop growth and yield losses if weeds are not managed well. Therefore, this research work was conducted to study the establishment percentage and weeds of rice under different rice establishment methods and weed management practices during kuruvai seasons of 2019-20 and 2020-21 with five main plots as establishment methods and six weed management practices as sub-plots in split-plot design on clay loam soil. The results demonstrated highest establishment percentage, WCE% and lesser weeds population obtained under SRI method of rice transplanting. All the herbicides reduced the weed population significantly as compared to weedy check. Pretilachlor 6% GR + bensulfuron methyl 0.6% (PE) and bispyribac sodium 10% SC (POE) reduced the weed population. Maximum reduction in yield due to weeds served in weedy check plot and lowest was recorded in PE followed by POE herbicidal application plot. Application of PE pretilachlor+bensulfuron methyl 0.6% @ 10 kg/ha under SRI method of transplanting resulted in highest average weed control efficiency.

First Report of Colletotrichum truncatum Causing Anthracnose of Green Foxtail (Setaria viridis) in China.

Green foxtail (Setaria viridis (L.) Beauv.), belonging to the family Gramineae, is a monocotyledonous plant that is distributed in tropical and subtropical regions of the world. S. viridis is one of the most abundant weeds in corn, soybean, rice and other major crops in China, which competes with crops for light, moisture and nutrients, leading to yield losses. In September 2021, an unknown leaf spot disease was observed on the leaves of S. viridis in many greenhouses of Xinkou town, Xiqing district, Tianjin, China (116.95729, 39.09088), under cloudy and high humid conditions after a week of rain. Over 60% of the weeds were observed with leaf spots in 28 greenhouses of XinKou town. The characteristics of the disease were observed and investigated. Initial symptoms were brown spots of 1 to 5 mms, longitudinal elliptic, round, or spindle-shaped lesions on leaves of S. viridis. These spots continued to spread shortly after the onset of the symptoms. At the late-stage disease, the spots' edges were dark brown and irregular. Eventually, the center of the spots turned grayish-white and became thinner and drier until fracture. To investigate the disease, symptomatic weed leaves were separated and small patches with infected spots were cut out. Diseased tissues (3×3 mm) were disinfected with 75% alcohol for 30s  35s, rinsed three times with sterile distilled water and then placed on potato dextrose agar (PDA) at 25°C with a 12-h photoperiod for 7 days in incubators (RXZ-280C, Ningbo, China). With the pathogen growing on the PDA, three mycelia with uniform morphology were observed, which were named SVCT-01, SVCT-02, and SVCT-03, respectively. These mycelia were transferred and cultured for daily observation. The color of these mycelia on PDA appeared gray at first, which eventually turned to grayish black with numerous black microsclerotia, setae, and a few aerial mycelia after 7 days. The setae were 75 to 120 ×3.5 to 5 μm, with elliptic to claviform appressoria. Conidia were hyaline, falcate, unicellular, 16 to 25 × 2.6 to 3.8 μm (n=50). All characteristics of isolates were consistent with the description of Colletotrichum truncatum (Sutton, 1992). Pathogenicity testing was conducted on 3-leaves-stage S. viridis seedlings. Conidial suspension (106 conidia/mL) of isolates were sprayed on 20 S. viridis seedlings with the suspension of each isolate was sprayed on 10 seedlings. Ten seedlings sprayed with sterilized distilled water were used as the control. Three replicates were performed on each treatment. The treatment plants were maintained in the incubator (25°C, relative humidity > 80%, 12-h photoperiod). Typical leaf spot symptoms were observed on inoculated leaves after 7 days, the control leaves remained symptomless. The fungus reisolated from the lesions of diseased leaves were morphological and molecularly identical to the inoculated isolates. The results echo with Koch's postulates，suggesting that the obtained isolates SVCT-01, SVCT-02 and SVCT-03 are potential pathogen in Setaria viridis. To confirm the species' identity, total genomic DNA of isolates were extracted using a Fungal DNA Kit (GBCBIO, Guangzhou, China). Sequences of internal transcribed spacer (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), actin (ACT), and β-tubulin (TUB2) regions were identified via PCR (Guerber et al, 2003; Weir et al, 2012). The sequences of SVCT-01, SVCT-02 and SVCT-03 showed more than 99% homology with Colletotrichum truncatum strains CBS:151.35 (GenBank Accession No. GU227862, GU228254, GU227960, GU228156) (Damm, 2009). The sequences of SVCT-01 were deposited in GenBank as a representative isolate under the accession numbers OL629177, OL627527, OM040388, OM040389. Maximum likelihood trees based on concatenated sequences of the four genes were constructed using MEGA7.0. The results showed that the strains isolated from Setaria viridis were closely related to Colletotrichum truncatum with 100% bootstrap support. According to morphological, pathological characteristics, and multilocus phylogenetic analysis, the isolated strains (SVCT-01, SVCT-02 and SVCT-03) from S. viridis were identified as Colletotrichum truncatum (Weir et al, 2012). Colletotrichum sp. is a significant plant pathogen that was previously reported causing anthracnose on Setaria sp. Up to now, it has been reported that C. graminicola has infected nine species of Setaria sp. Such as Setaria glauca in New Zealand (Pennycook, 1989) and Setaria pumila in Zimbabwe (Lenne, 1990). In 1979s, C.graminicola was obtained from Setaria lutescens in China (Tai, 1979). To our knowledge, this is a new host record for Colletotrichum truncatum causing anthracnose on S. viridis in China. Colletotrichum truncatum spread rapidly and caused serious disease to Setaria viridis. We hope to discovery a biocontrol method against weed on non-host cultivated plants through the production of secondary metabolites by C. truncatum.

Metabolic cross-resistance to florpyrauxifen-benzyl in barnyardgrass (Echinochloa crus-galli) evolved before the commercialization of Rinskor™

AbstractHerbicide options for selective control of monocot weeds in rice (Oryza sativa L.) have historically been limited to a few modes of action such as inhibitors of acetolactate synthase (e.g., penoxsulam, imazamox), photosystem II (e.g., propanil), and acetyl-CoA carboxylase (e.g., cyhalofop). Florpyrauxifen-benzyl (Rinskor™) is a synthetic auxin molecule introduced to the U.S. rice herbicide market in 2018, providing broad-spectrum weed control (monocots and dicots), including hard-to-control species such as barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.], along with postemergence rice selectivity at very low use rates. Within the year of commercialization, field agronomists and academics identified E. crus-galli escapes in some areas where florpyrauxifen-benzyl had been sprayed. Further evaluation under controlled environments confirmed that those plants were able to survive florpyrauxifen-benzyl application at the label rate. Here, we identify the mechanism of resistance to florpyrauxifen-benzyl and penoxsulam in two E. crus-galli populations from Arkansas (AR-27) and Missouri (MO-18). Using high-resolution mass spectrometry, we compared the two resistant biotypes with known susceptible plants regarding their ability to metabolize florpyrauxifen-benzyl, florpyrauxifen-acid, and penoxsulam in planta. We discovered that the resistant plants share a common resistance mechanism to florpyrauxifen-benzyl and penoxsulam, involving hydrolysis of a methoxy group (likely mediated by a cytochrome P450 monooxygenase) followed by glucose conjugation. Given that penoxsulam has been widely used in rice fields for the past decade, these data suggest that some populations of E. crus-galli may have evolved resistance before the commercialization of florpyrauxifen-benzyl.

Seed biology of alkali barnyardgrass (Echinochloa crus-galli var. zelayensis) and junglerice (Echinochloa colona) for improved management in direct-seeded rice

AbstractAlkali barnyardgrass [Echinochloa crus-galli var. zelayensis (Kunth) Hitchc] and junglerice [Echinochloa colona (L.) Link] are problematic annual weeds in direct-seeded rice (Oryza sativa L.) fields in China. The emergence ecology of the two weed species may differ in response to environmental factors. Laboratory and screenhouse experiments were conducted to evaluate the effects of light, burial depth, mulching with wheat (Triticum aestivum L.) residue, and time and depth of flooding on the emergence of the two weed species collected from Nanjing, China. Light strongly increased seed germination. Under dark conditions, E. crus-galli seed germination (85%) was higher than that of E. colona (70%). The seeds of both species exhibited the greatest germination (90% for E. crus-galli and 80% for E. colona) when sown on the soil surface, and emergence decreased with increasing soil burial depth. Burial depths of 2.2 and 1.4 cm reduced seedling emergence by 50% for E. crus-galli and E. colona, respectively. No emergence was found at a depth of 6 cm. The seedling emergence for E. colona was lower than for E. crus-galli at the same soil burial depth. Mulching with wheat residue considerably reduced the seedling emergence and aboveground biomass of both species. The inhibitory effect of mulching with wheat residue on E. colona was more notable than on E. crus-galli. Early and deep flooding significantly suppressed the emergence, height, and biomass of E. crus-galli and E. colona, especially E. colona. The results gained from this study could provide fundamental ecological knowledge for managing Echinochloa species in direct-seeded rice systems.

Double-spraying with different routes significantly improved control efficacies of herbicides applied by unmanned aerial spraying system: A case study with rice herbicides

An unmanned aerial spraying system (UASS) is one of the most important systems for herbicide applications. To date, no study has compared the control efficacies of herbicides applied by UASSs with different application strategies against weeds. We applied post-emergence (POST) herbicides using a six-rotor UASS on rice (Oryza sativa) fields with different spraying volumes (22.5, 30, 45, and 60 L ha−1) and different spraying route strategies (one-time spraying or two flight sorties routed in length and breadth). The spraying volume significantly affected (P < 0.05) control efficacies against Echinochloa spp., Leptochloa chinensis, Ammannia baccifera, Monochoria vaginalis, Cyperus difformis, and overall weeds. The spraying route strategy significantly affected control efficacies against Echinochloa spp., Leptochloa chinensis, Ammannia baccifera, and overall weeds. Treatment with the double-spraying strategy significantly increased the control efficacies against Echinochloa spp. and Leptochloa chinensis compared with one-time spraying. For weeds susceptible to herbicides applied, treatments with a spraying volume of 30 L ha−1 showed control efficacies >90%; for grassy weeds, UASS applications with double-spraying routed in length and breadth with a spraying volume of 60 L ha−1 did not show a significant difference with the manual spraying with a spraying volume of 450 L ha−1 in control efficacies. This study revealed different optimal spraying volumes for controlling different groups of rice weeds and demonstrated a new spraying strategy for UASS applications that can be used to improve herbicide application practices with UASSs.

John Caseley 1935–2022: a Life with Weeds

Former Outlooks on Pest Management board member John Caseley is remembered for his significant contribution to weed science in a career spanning five decades which earned him the respect of his peers around the world. John passed away recently at the age of 87. John’s extensive publication list demonstrates his capacity for collaboration with scientists in the UK and around the world. His enthusiastic and extrovert character made him not only a welcome colleague but also a frequent speaker at meetings and conferences. He was a regular contributor to the annual Brighton Weed control conferences and presented at numerous international meetings including in USA, Israel, Australia and in Europe. His international reach was further enhanced by collaboration on publications that to this day remain essential sources of information including a 1994 United Nations published book on Weed Management for Developing Countries, co-edited with Ricardo Labrada and Chris Parker and a volume from 2000 on Prevention and Management of Herbicide Resistant Weeds in Rice co-authored by Bernal Valverde and Charlie Riches. The latter has been downloaded many thousands of times in both English and Spanish versions. He was always keen to encourage others and served for many years on the editorial board of the Outlooks on Pest Management Journal and committees of the Society of Chemical Industry. John’s qualities were especially appreciated by many postdoctoral and post-graduate students from overseas who benefitted from his wise council and mentoring and who went on to become distinguished weed scientists in their own countries.

Effect of depth of flooding on growth and fecundity of fall panicum (Panicum dichotomiflorum)

AbstractFall panicum is the most prevalent and problematic weed in rice in Florida. Outdoor studies were conducted in 2021 to determine the effect of flooding on fall panicum growth and its ability to produce and develop panicles. Fall panicum at the two- to four-leaf and four- to six-leaf stages of development were flooded in stock tanks maintained at flooding depths of 0, 10, 15, 20, and 30 cm for 56 d. Plant height, number of tillers and leaves, leaf area, shoot biomass, root biomass, and panicle branches for both fall panicum leaf stages of development decreased with increasing flooding depth. Fall panicum flooded at the two- to four-leaf stage survived flood depth of 15 cm, whereas plants flooded at the four- to six-leaf stage survived and emerged from a flood depth of up to 20 cm. The 10-cm flood depth resulted in the tallest plants with more leaves, tillers, and leaf area for both growth stages. The probability of fall panicum survival and ability to produce panicles decreased as flood depth increased. Flood depth required for 50% survival for four- to six-leaf-stage plants was estimated to occur at 14 cm, whereas that for plants at the two- to four-leaf stage occurred at 12 cm. The flood depth required to reduce panicle branch production by 50% was estimated to be 15 and 20 cm for two- to four-leaf, and four- to six-leaf-stage plants, respectively. These results show that flooding &gt;10 cm is required to significantly reduce fall panicum survival and ability to produce panicles. Since flood level in rice is usually maintained at an average of 10 cm, chemical weed control will be important to supplement flooding for effective control of fall panicum in rice.

Effect of Bt traits on transgenic rice’s growth and weed competitiveness

Transgene escape could lead to genetically modified rice establishing wild populations in the natural environment and competing for survival space with weeds. However, whether the expression of the Bacillus thuringiensis (Bt) gene in rice will alter the relationship between transgene plants and weeds and induce undesirable environmental consequences are poorly understood. Thus, field experiments were conducted to investigate the weed competitiveness and assess the ecological risk of transgenic Bt rice under herbicide-free and lepidopterous pest-controlled environments. Results showed that weed–rice competition in the direct-sowing (DS) field was earlier and more severe than that in the transplanting (TP) field, which resulted in a significant decrease in biomass and yield in DS. However, conventional Bt and non-Bt rice yield was not significantly different. The weed number, weed coverage ratio, and weed diversity of conventional Bt rice were significantly higher than those of non-Bt rice at the early growth and mature stages, especially in DS plots, suggesting that Bt traits did not increase the weed competitiveness of transgenic rice and had no negative effect on weed diversity. Grain yield and weed number varied between different hybrid rice lines, but those differences were insignificant between Bt and non-Bt rice. The number of insects increased with the increase of weeds in hybrid rice plots, whereas the insect number and diversity did not display a significant difference between Bt and non-Bt rice. Therefore, the ecological risk of transgenic Bt rice is comparable to non-Bt rice.

Estimating Carbon Capture Potential of Fallow Weeds in Rice Cropping Systems

Weeds occurred during the fallow season can well perform the function of carbon (C) capture due to receiving little human disturbance. This study aimed to evaluate the C capture potential of fallow weeds in rice (Oryza sativa L.) cropping systems. A six-region, two-year on-farm investigation and a three-year tillage experiment were conducted to estimate C capture in fallow weeds in rice cropping systems. The on-farm investigation showed that the average mean C capture by fallow weeds across six regions and two years reached 112 g m–2. The tillage experiment indicated that no-tillage practices increased C capture by fallow weeds by 80% on average as compared with conventional tillage. The results of this study not only contribute to an understanding of C capture potential of fallow weeds in rice cropping systems, but also provide a reference for including fallow weeds in the estimation of vegetative C sink.

Monoclonal antibody production and development of immunochromatographic strip assays for screening of the herbicide bispyribac-sodium in rice.

Bispyribac-sodium (BIS) is a new broad-spectrum and efficient herbicide, which is widely used for the control of weeds in rice. To protect the human body from the threat of BIS exposure, it is essential to establish a sensitive and simple detection method. In this work, a high-affinity monoclonal antibody against BIS was produced for the first time, and a colloidal gold immunochromatographic strip assay (ICSA) was developed to screen for BIS in rice samples. The visual limit of detection and the calculated limit of detection of the ICSA were 0.2 μg kg-1 and 0.018 μg kg-1, respectively, which could be accurately obtained within 8 min. The average recoveries of BIS ranged from 90.0% to 109.0% in tests, with CVs ranging from 4.0% to 8.9% for rice samples. Therefore, our ICSA would be a good option for the sensitive and rapid detection of BIS in rice samples.

A novel intrusion detection system for IIoT using inception convolutional neural network

The purpose of this study is to compare the accuracy of several deep-learning models for the identification of rice weed. In this study, 1500 datasets of local rice and 1000 datasets of weed were resized and applied to the input size of the network, respectively. A total of 70% of the data were used for training, and the remaining 30% were used for validation. MATLAB R2018a was used to construct the AlexNet pre-trained model using a transfer learning strategy, and by changing the AlexNet model, RiceWeedNet, a convolutional neural network, was created. Metrics such as network accuracy, recognition accuracy, precision, and recall were used to assess both models’ performances. While the test set’s identification accuracy is 97.713415%, its precision is 0.9776, and its recall value is 0.9803. The RiceWeedNet model achieved a network accuracy of 100%. A network accuracy of 90% and a recognition accuracy of 73.780488% were reported by the AlexNet model, respectively. The created model may be used instead of conventional weed detectors.