Insecticide Resistance Research Articles

Insecticide Susceptibility Tests of Aedes albopictus Skuse in Geothermal Hot Springs, Malaysia

Dengue fever is a major public health concern, including more than 20,000 reported dengue cases annually in Malaysia. Aedes albopictus is the primary vector of chikungunya and secondary vector of dengue and Zika viruses. The susceptibility to dichlorodiphenyltrichloroethane (DDT), dieldrin, fenitrothion, pirimiphos-methyl, propoxur and bendiocarb of Ae. albopictus from four hot springs in Selangor, Malaysia was ascertained in accordance with World Health Organization guidelines. Threeto fi ve-day old female mosquitoes which were reared from eggs collected by ovitraps were exposed to discriminating dosages of insecticides for 1 hr recommended exposure period, and the 24 h mortality was recorded. The Kerling Hot spring (KERL) population was susceptible to six insecticides. All four fi eld populations were susceptible to pirimiphos-methyl 0.25% indicating it could be considered as a replacement insecticide for future vector control operations. Propoxur is the second in line as an alternative insecticide based on mortality > 80.0%. Nevertheless, it is necessary to confi rm their crossresistance to pyrethroids and other organophosphates before using them in rotation in the management of insecticide resistance.

Joint Action of Selective Herbicides used in Paddy Field on Control of Lemna minor L.

To minimise herbicide inputs, reduce environmental burdens, and delay the evolution of herbicide resistance, it is of the utmost significance to study the interaction between herbicides. This may be accomplished by selecting the optimal combination, which, through synergy, delivers more cost-effective weed control than a single herbicide. Under laboratory conditions, interactions between binary mixtures of bensulfuron, propanil, 2,4-D, or bentazon on chlorophyll reduction of Lemna minor were investigated using the Additive Dose Model. Mixtures of propanil/2,4-D resulted in low antagonism whereas strong antagonism was evident in bensulfuron-methyl/propanil. Combinations of bensulfuron/bentazon and bensulfuron/2,4-D led to moderate antagonism. By contrast, propanil in combination with bentazon demonstrated a modest degree of synergism. The findings of this study could provide good guideline and insights when mixing two herbicides for weed control in rice fields and other aquatic environment.

Field-evolved pyrethroid resistance in Tychius picirostris (Coleoptera: Curculionidae) populations in Oregon white clover seed crops.

The clover seed weevil, Tychius picirostris Fabricius, a serious pest of white clover, Trifolium repens L., grown for seed in western Oregon, causing feeding damage to flowers and developing seeds. Since 2017, white clover seed producers have anecdotally reported T. picirostris control failures using foliar pyrethroid insecticide applications. This mode of action (MoA) is an important chemical control option for T. picirostris management. To evaluate insecticide resistance selection to pyrethroids (bifenthrin) and other MoAs labeled for T. picirostris management (malathion and chlorantraniliprole), adult populations were collected from 8 commercial white clover grown for seed fields in the Willamette Valley, OR, in 2022 and 2023. Among collected Oregon populations, very high resistance ratios (RR50 = 178.00-725.67) were observed to technical grade bifenthrin and low to high resistance ratios (RR50 = 7.80-32.80) to malathion in surface contact assays compared to a susceptible Canadian field population. Moreover, >2.73 times the labeled rate of formulated product containing bifenthrin as the sole MoA was required to kill >50% of T. picirostris in topical assays. Synergistic assays with a mixed-function oxidase inhibitor, an esterase inhibitor, and a glutathione-S-transferase inhibitor revealed phase I and II detoxification enzymes are present in Oregon T. picirostris populations and confer metabolic resistance to bifenthrin. This is the first report of T. picirostris insecticide resistance selection to pyrethroid and organophosphate insecticides. Results will inform continued monitoring and insecticide resistance management strategies to slow the evolution of T. picirostris insecticide resistance selection in Oregon's white clover seed production.

Evidence of active oviposition avoidance to systemically applied imidacloprid in the Colorado potato beetle.

Agricultural pests can develop behavioral resistance to insecticides by choosing to feed or oviposit on insecticide-free hosts. As young larvae have relatively low mobility, oviposition preferences from female adults may play a critical role in shaping the evolutionary trajectory of pest populations. While oviposition avoidance of insecticide-treated hosts was found in different agriculture pests, it remains unclear whether female adults actively choose to occupy insecticide-free hosts. To address this question, we investigated feeding and oviposition preferences between imidacloprid-treated and imidacloprid-free plants in the Colorado potato beetle, Leptinotarsa decemlineata Say, a major potato pest. We performed behavioral choice assays on two strains that differed in both fecundity and insecticide resistance. We found that one strain preferred to feed on the insecticide-free plants and that this preference is not innate. Meanwhile, the other strain chose plants for feeding and oviposition randomly. Further analyses of the moving patterns of the beetles suggested that the oviposition preference in the first strain is likely due to active learning.

Insecticide resistance level of Aedes aegypti L. (Diptera: Culicidae) in northern Mexico

Objective: To determine the response of the larvae of three Ae. aegypti populations from the Mexican North Pacific region to insecticides with different mode of action.
 Design/Methodology/Approach: Three colonies were obtained placing ovitramps in peridomestic sites in Guadalajara (Jalisco), Culiacan (Sinaloa), and La Paz (Baja California Sur). Based on the methodology proposed by WHO, the bioassays were carried out with F1 larvae in the early fourth instar.
 Results: The larvae from the three field colonies had high resistance to permethrin and low resistance to deltamethrin; however, they were susceptible to Spinosad and Bacillus thuringiensis var. Israelensis. The Culiacan strain showed a high resistance to the malathion and propoxur insecticides.
 Study Limitations/Implications: The results provided valuable information about the response of these populations to insecticides, which are useful to establish resistance in the lab. Consequently, further studies should be carried out to complement the information obtained in these field tests.
 Findings/Conclusions: The data indicated resistance levels to pyrethroid insecticides (mainly permethrin), as well as to organophosphates and carbamates.

Heat shock proteins, thermotolerance, and insecticide resistance in mosquitoes.

Mosquitoes transmit pathogens that pose a threat to millions of people globally. Unfortunately, widespread insecticide resistance makes it difficult to control these public health pests. General mechanisms of resistance, such as target site mutations or increased metabolic activity, are well established. However, many questions regarding the dynamics of these adaptations in the context of developmental and environmental conditions require additional exploration. One aspect of resistance that deserves further study is the role of heat shock proteins (HSPs) in insecticide tolerance. Studies show that mosquitoes experiencing heat stress before insecticide exposure demonstrate decreased mortality. This is similar to the observed reciprocal reduction in mortality in mosquitoes exposed to insecticide prior to heat stress. The environmental shifts associated with climate change will result in mosquitoes occupying environments with higher ambient temperatures, which could enhance existing insecticide resistance phenotypes. This physiological relationship adds a new dimension to the problem of insecticide resistance and further complicates the challenges that vector control and public health personnel face. This article reviews studies illustrating the relationship between insecticide resistance and HSPs or hsp genes as well as the intersection of thermotolerance and insecticide resistance. Further study of HSPs and insecticide resistance could lead to a deeper understanding of how environmental factors modulate the physiology of these important disease vectors to prepare for changing climatic conditions and the development of novel strategies to prevent vector-borne disease transmission.

Microbiome-Mediated Strategies to Manage Major Soil-Borne Diseases of Tomato

The tomato (Solanum lycopersicum L.) is consumed globally as a fresh vegetable due to its high nutritional value and antioxidant properties. However, soil-borne diseases can severely limit tomato production. These diseases, such as bacterial wilt (BW), Fusarium wilt (FW), Verticillium wilt (VW), and root-knot nematodes (RKN), can significantly reduce the yield and quality of tomatoes. Using agrochemicals to combat these diseases can lead to chemical residues, pesticide resistance, and environmental pollution. Unfortunately, resistant varieties are not yet available. Therefore, we must find alternative strategies to protect tomatoes from these soil-borne diseases. One of the most promising solutions is harnessing microbial communities that can suppress disease and promote plant growth and immunity. Recent omics technologies and next-generation sequencing advances can help us develop microbiome-based strategies to mitigate tomato soil-borne diseases. This review emphasizes the importance of interdisciplinary approaches to understanding the utilization of beneficial microbiomes to mitigate soil-borne diseases and improve crop productivity.

Kdr genotyping and the first report of V410L and V1016I kdr mutations in voltage-gated sodium channel gene in Aedes aegypti (Diptera: Culicidae) from Iran

BackgroundAedes aegypti is the main vector of arboviral diseases worldwide. The species invaded and became established in southern Iran in 2020. Insecticide-based interventions are primarily used for its control. With insecticide resistance widespread, knowledge of resistance mechanisms is vital for informed deployment of insecticidal interventions, but information from Iranian Ae. aegypti is lacking.MethodsFifty-six Ae. aegypti specimens were collected from the port city of Bandar Lengeh in Hormozgan Province in the South of Iran in 2020 and screened for kdr mutations. The most common kdr mutations in Latin America and Asia (V410L, S989P, V1016G/I and F1534C), especially when present in combinations, are highly predictive of DDT and pyrethroid resistance were detected. Phylogenetic analyses based on the diversity of S989P and V1016G/I mutations were undertaken to assess the phylogeography of these kdr mutations.ResultsGenotyping all four kdr positions of V410L, S989P, V1016G/I and F1534C revealed that only 16 out of the 56 (28.57%) specimens were homozygous wild type for all kdr mutation sites. Six haplotypes including VSVF (0.537), VSVC (0.107), LSVF (0.016), LSIF (0.071), VPGC (0.257) and LPGC (0.011) were detected in this study. For the first time, 11 specimens harbouring the V410L mutation, and 8 samples with V1016I mutation were found. V410L and V1016I were coincided in 8 specimens. Also, six specimens contained 1016G/I double mutation which was not reported before.ConclusionsThe relatively high frequency of these kdr mutations in Iranian Ae. aegypti indicates a population exhibiting substantial resistance to pyrethroid insecticides, which are used widely in control operations and household formulations. The detection of the 410L/1016I kdr mutant haplotype in Iranian Ae. aegypti suggests possible convergence of invasive populations from West Africa or Latin America. However, as Iran has very limited maritime/air connections with those African countries, a Latin American origin for the invasive Ae. aegypti in Iran is more plausible. Graphical abstract

What is the value of rotations to insecticide resistance management?

Rotations have been the cornerstone of insecticide resistance management for many decades. In recent years, there has been a resurgence of interest in the use of insecticide mixtures, particularly based on new theoretical models. Here, we present a perspective on the value of rotations to insecticide resistance management, focusing on the interpretation of influential theoretical models. The principles of resistance management have previously been reduced to moderation, saturation and multiple attack. Alongside mixtures and mosaics, rotations have been presented as a strategy of multiple attack in using more than one insecticide. Three explanations have been offered for how rotations delay resistance evolution: counterselection from resistance cost, the relaxation of selection and intergenerational redundant kill. We show that all three explanations can make sense of the comparison of rotations with another resistance-management strategy but have failed to elucidate the principle at work. Overall, we argue that rotations work by moderation, delaying resistance to insecticides through the use of each insecticide less over time. We suggest that the principles of resistance management are recast as moderation, saturation and redundancy. When rotations and mixtures are not conceptualised as competing methods of multiple attack, these strategies can more obviously work together through the complementary principles of moderation and redundancy. Whether solo products or a mixture of products are used, rotations are an effective method of risk management, preserving the arsenal of all effective insecticides for longer. A successful resistance-management plan should make appropriate use of all the principles of resistance management. © 2024 Society of Chemical Industry.

Large and complete datasets, and modelling reveal the major determinants of physiological and behavioral insecticide resistance of malaria vectors

Large and complete datasets, and modelling reveal the major determinants of physiological and behavioral insecticide resistance of malaria vectors

Key Contributions of the Overexpressed Plutella xylostella Sigma Glutathione S-Transferase 1 Gene (PxGSTs1) in the Resistance Evolution to Multiple Insecticides.

The overexpression of insect detoxification enzymes is a typical adaptive evolutionary strategy for insects to cope with insecticide pressure. In this study, we identified a glutathione S-transferase (GST) gene, PxGSTs1, that exhibited pronounced expression in the field-resistant population of Plutella xylostella. By using RNAi (RNA interference), the transgenic fly models, and quantitative real-time polymerase chain reaction (RT-qPCR) methods, we confirmed that the augmented expression of PxGSTs1 mediates the resistance of P. xylostella to various types of insecticides, including chlorantraniliprole, novaluron, λ-cyhalothrin, and abamectin. PxGSTs1 was found to bolster insecticide resistance in two ways: direct detoxification and enhancing antioxidative defenses. In addition, our findings demonstrated that pxy-miR-8528a exerts a pivotal influence on forming insecticide resistance in P. xylostella by downregulating PxGSTs1 expression. In summary, we elucidated the multifaceted molecular and biochemical underpinnings of PxGSTs1-driven insecticide resistance in P. xylostella. Our results provide a new perspective for understanding the insecticide resistance mechanism of P. xylostella.

CRISPR/Cas9-mediated homology donor repair base editing system to confer herbicide resistance in maize (Zea mays L.)

Weed infestation is a significant concern to crop yield loss, globally. The potent broad-spectrum glyphosate (N-phosphomethyl-glycine) has a widely utilized herbicide, acting on the shikimic acid pathway within chloroplast by inhibiting 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). This crucial enzyme plays a vital role in aromatic amino acid synthesis. Repurposing of CRISPR/Cas9-mediated gene-editing was the inflection point for generating novel crop germplasm with diverse genetic variations in essential agronomic traits, achieved through the introduction of nucleotide substitutions at target sites within the native genes, and subsequent induction of indels through error-prone non-homologous end-joining DNA repair mechanisms. Here, we describe the development of efficient herbicide-resistant maize lines by using CRISPR/Cas9 mediated site-specific native ZmEPSPS gene fragment replacement via knock-out of conserved region followed by knock-in of desired homologous donor repair (HDR-GATIPS-mZmEPSPS) with triple amino acid substitution. The novel triple substitution conferred high herbicide tolerance in edited maize plants. Transgene-free progeny harbouring the triple amino acid substitutions revealed agronomic performances similar to that of wild-type plants, suggesting that the GATIPS-mZmEPSPS allele substitutions are crucial for developing elite maize varieties with significantly enhanced glyphosate resistance. Furthermore, the aromatic amino acid contents in edited maize lines were significantly higher than in wild-type plants. The present study describing the introduction of site-specific CRISPR/Cas9- GATIPS mutations in the ZmEPSPS gene via genome editing has immense potential for higher tolerance to glyphosate with no yield penalty in maize.

Insect Gut Microbiota and Pesticide Degradation in Response to Innate Metabolites- a Review

Insects host a diverse microbiota in their gut, encompassing bacteria, fungi, viruses, and archaea, influencing their physiology, nutrition, and overall health. The composition of these microbial communities varies with factors like insect species, diet, and the environment. Insect gut microbiota serve pivotal roles such as aiding digestion, synthesizing essential nutrients, safeguarding against pathogens, and detoxifying toxins, including insecticides. A particularly promising facet of their function lies in influencing the metabolism of insecticides. These gut microbiotas can either augment or diminish insecticide toxicity through mechanisms like enzymatic breakdown, sequestration, target site alteration, or modulation of the insect's immune response. Understanding these interactions is paramount for devising sustainable pest management strategies. This review explores into insect gut microbiota, their impact on insecticide susceptibility, and the potential use of microbial metabolites in eco-friendly pest control. We explore pesticide degradation mechanisms, the consequences of microbiota disruption on susceptibility, and the role of microbiota-produced metabolites in shaping pesticide efficacy. Ultimately, we highlight the potential of microbiota manipulation as a strategy to enhance insecticide effectiveness and combat pesticide resistance in pest management.

Impact of a spatial repellent intervention on Anopheles kdr insecticide resistance allele in Sumba, Indonesia

BackgroundThe emergence of insecticide resistance and outdoor transmission in malaria-endemic areas underlines the urgent need to develop innovative tools, such as spatial repellents (SR), that may circumvent this residual transmission. With limited options for effective insecticides, regular resistance monitoring is warranted for selecting and using appropriate tools. This study evaluates the pyrethroid knockdown resistance (kdr) allele before and after implementing a transfluthrin-based spatial repellent (SR) intervention in placebo-treated clusters.MethodsThis study looks at the frequency distribution of the kdr allele in Sumba Island from June 2015 to August 2018. Insecticide susceptibility tests were carried out on female Anopheles sp. aged 3–5 days against permethrin 21.5 μg/ml, deltamethrin 12.5 μg/ml, and transfluthrin 10 μg/ml using CDC bottle assay. PCR sequencing of representative samples from adult mosquito collections and insecticide tests revealed the presence of kdr mutations (L1014F and L1014S) in the VGSC gene.ResultsA total of 12 Anopheles species, Anopheles tesselatus, Anopheles. aconitus, Anopheles barbirostris, Anopheles kochi, Anopheles annularis, Anopheles maculatus, Anopheles sundaicus, Anopheles flavirostris, Anopheles balabacensis, Anopheles indefinitus, Anopheles subpictus, and Anopheles vagus were analysed. Anopheles vagus and An. sundaicus predominated in the larval populations. Susceptibility assays for all insecticides identified fully susceptible phenotypes in all species examined. Anopheles increasing frequency of kdr mutant alleles during the 3 year SR deployment was observed in both SR-treated and placebo areas, a statistically significant increase occurred in each arm. However, it is unclear how significant SR is in causing the increase in mutant alleles. The L1014S, knockdown resistance east type (kdr-e) allele was detected for the first time among the mosquito samples in this study. The L1014F, knockdown resistance west type (kdr-w) allele and heteroduplex form (wild-type—mutant) were found in almost all Anopheles species examined, including An. vagus, An. aconitus, An. subpictus, An. tesselatus, An. annularis, An. flavirostris and An. sundaicus.ConclusionThe presence of fully susceptible phenotypes over time, along with an increase in the frequency distribution of the L1014F/S mutations post-intervention, suggest drivers of resistance external to the study, including pyrethroid use in agriculture and long-lasting insecticidal nets (LLINs). However, this does not negate possible SR impacts that support resistance. More studies that enable the comprehension of possible SR-based drivers of resistance in mosquitoes need to be conducted.

Herbicide‐resistant weeds from dryland agriculture in Argentina

AbstractWe reviewed and performed a quantitative synthesis on herbicide‐resistant weeds from rain‐fed crops in Argentina. Twenty‐four weed species distributed in the main extensive crops (soybean, maize, wheat, barley, oilseed rape, sunflower, chickpea and peanut) have evolved herbicide resistance. Of the total, 54% are grasses, 88% are annual species and 63% are cross‐pollinated species. The most representative families were Poaceae with 54% resistant species, followed by Brassicaceae with 17%, and Asteraceae with 13%. Buenos Aires, Santa Fe and Córdoba were the provinces with the most documented cases of resistance (35%, 33% and 30%, respectively). The proportion of cases resistant to pre‐emergence herbicides was 10%, whereas the proportion of cases resistant to post‐emergence herbicides was 90%. Glyphosate was the herbicide with the highest incidence (92%) of resistance among weed species, followed by 29% of species that evolved resistance to ALS‐inhibiting herbicides. Whereas resistance to auxin‐like herbicides comprised 17% of the weed species, acetyl‐CoA carboxylase (8%) and protoporphyrinogen oxidase (4%) inhibiting herbicides showed the least incidence of resistance evolution among weeds. The highest number of resistant species was identified in soybean (19), followed by maize (13), wheat/barley (10) and fallow (9). Weed species with a higher number of resistant populations to a higher number of herbicide mode of action were Amaranthus hybridus, A. palmeri, Lolium multiflorum and Raphanus sativus. The change in the production system since the mid‐1990s, based on the use of herbicides (glyphosate mainly) to control weeds, is likely to account for the notorious increase in the average rate of evolution of herbicide‐resistant weeds in Argentina.

Identification of potent inhibitors targeting Tribolium castaneum GSTe2 via structure-based screening and molecular dynamics simulation

Red flour beetle, Tribolium castaneum, has a major negative impact during storage of agricultural products and reveals the negative impacts on human health. Insect-specific epsilon glutathione S-transferase (GSTs) which requires reduced glutathione (GSH) as an essential substrate not only develop insecticide resistance but also play important role in insect metamorphosis. Inhibition of the insect metamorphosis and the development of insecticide resistance could play an important role in pest control, so T. castaneum GSTe2 (TcGSTe2) in our previous study could be an important target protein for this purpose. This study aimed to find a potential TcGSTe2 inhibitors through in silico mothods, including molecular modeling, molecular docking, ADMET assay, followed by molecular dynamics (MD) simulation, principal component analysis and MM/PBSA analysis. The results showed that ZINC000169293362 and ZINC000095566957 were selected as potential TcGSTe2 inhibitors with high-binding affinity and without any toxicity from 3618 of GSH-like compounds obtained from ZINC database. MD simulation results revealed that TcGSTe2-ZINC000169293362 had more stability than that of reference GSH. Moreover, TcGSTe2-ZINC000169293362 and TcGSTe2-ZINC000095566957 showed lower binding free energy (−27.53 ± 0.16 kcal/mol and −18.83 ± 0.15 kcal/mol, respectively) compared with TcGSTe2-GSH (−8.90 ± 0.30 kcal/mol). This study could provide new insight into reduction of insecticide resistance and be used to design new inhibitors of insect GSTs. Communicated by Ramaswamy H. Sarma

Uridine diphosphate glucosyltransferases are involved in spinosad resistance in western flower thrips Frankliniella occidentalis (Pergande)

Uridine diphosphate glucosyltransferases (UGTs) play crucial roles in the insect detoxification system and are associated with pesticide resistance. Our previous transcriptomic analysis of spinosad-susceptible (Ivf03) and resistant (NIL-R) Frankliniella occidentalis revealed numerous upregulated UGT genes in the NIL-R strain, suggesting their potential contribution to spinosad resistance. To investigate this hypothesis, here we conducted UGT activity assays and spinosad induction experiments, employing RNA interference (RNAi) techniques for gene function validation. We found significantly elevated UGT activity in the NIL-R strain compared to Ivf03, with 5-nitrouracil showing a substantial synergistic effect on the resistant strain. Eighteen UGT genes were identified in F. occidentalis, with gene expansion and duplication observed within families UGT466, 467, and 468. Ten out of the eighteen UGTs exhibited higher expression levels in NIL-R, specifically FoUGT466B1, FoUGT468A3, and FoUGT468A4 consistently being upregulated across nymphs, males, and females. RNAi-based functional validation targeting these three UGT genes led to increased susceptibility to spinosad in a life stage-, sex-, and dose-dependent manner. These results indicate that UGTs are indeed involved in spinosad resistance in F. occidentalis, and the effects are dependent on life stage, sex, and dose. Therefore, sustainable control for F. occidentalis resistance should always consider these differential responses.

Three chemosensory proteins enriched in antennae and tarsi of Rhaphuma horsfieldi differentially contribute to the binding of insecticides

Antennae and legs (primarily the tarsal segments) of insects are the foremost sensory organs that contact a diverse range of toxic chemicals including insecticides. Binding proteins expressed in the two tissues are potential molecular candidates serving as the binding and sequestering of insecticides, like chemosensory proteins (CSPs). Insect CSPs endowed with multiple roles have been suggested to participate in insecticide resistance, focusing mainly on moths, aphids and mosquitos. Yet, the molecular underpinnings underlying the interactions of cerambycid CSPs and insecticides remain unexplored. Here, we present binding properties of three antenna- and tarsus-enriched RhorCSPs (RhorCSP1, CSP2 and CSP3) in Rhaphuma horsfieldi to eight insecticide classes totaling 15 chemicals. From the transcriptome of this beetle, totally 16 CSP-coding genes were found, with seven full-length sequences. In phylogeny, these RhorCSPs were distributed dispersedly in different clades. Expression profiles revealed the abundant expression of RhorCSP1, CSP2 and CSP3 in antennae and tarsi, thus as representatives for studying the protein-insecticide interactions. Binding assays showed that the three RhorCSPs were tuned differentially to insecticides but exhibited the highest affinities with hexaflumuron, chlorpyrifos and rotenone (dissociation constants <13 μM). In particular, RhorCSP3 could interact strongly with 10 of tested insecticides, of which four residues (Tyr25, Phe42, Val65 and Phe68) contributed significantly to the binding of six, four, three and four ligands, respectively. Of these, the binding of four mutated RhorCSP3s to a botanical insecticide rotenone was significantly weakened compared to the wildtype protein. Furthermore, we also evidenced that RhorCSP3 was a broadly-tuned carrier protein in response to a wide variety of plant odorants outside insecticides. Altogether, our findings shed light on different binding mechanisms and odorant-tuning profiles of three RhorCSPs in R. horsfieldi and identify key residues of the RhorCSP3-insecticide interactions.

Sequential herbicide application coupled with mulch enhances the productivity and quality of winter onion (Allium cepa L.) while effectively controlling the mixed weed flora

Weed control poses substantial difficulties for winter season onion (Allium cepa L.) cultivation in the north-western Indo-Gangetic Plains, primarily due to the constrained efficacy of the existing herbicides. To address this issue, a 2-year field study was conducted to assess the efficacy of pre- and post-emergence herbicides (pendimethalin, ethoxysulfuron, imazethapyr, and quizalofop-p-ethyl) individually and in combination with crop residue mulch for weed control in winter onion. The results revealed that using herbicides or mulches in isolation did not provide satisfactory weed control. However, the integration of natural mulch with pendimethalin followed by quizalofop-p-ethyl application proved to be the most effective weed control strategy, resulting in the least reduction in bulb yield (10.3%) compared to other treatments. On the contrary, combinations of pendimethalin with ethoxysulfuron or imazethapyr showed adverse effects on the onion crop and inflicted the highest yield losses among all treatments (78.6 and 83.4%, respectively). However, the combination of pendimethalin with quizalofop-p-ethyl coupled with crop mulch resulted in season-long weed control and over 80% bulb yield (36.58 t/ha) gains compared to the weed-free condition. These findings emphasize the efficacy of combining herbicides and mulches as an integrated weed management strategy for onions. By adopting such integrated approaches, farmers could improve weed control while maintaining bulb yield and quality, reducing the risks associated with herbicide resistance, and promoting sustainable onion production in the north-western Indo-Gangetic Plains.

Comparison of Carbon Footprint, Environment Impact, Efficacy and Benefit–Cost Ratio of Insecticide Resistance Management with Conventional Methods used by Thai Chinese Cabbage Farmers

Aim To evaluate and compare the carbon footprint, efficacy, and benefit-cost ratios of Chinese cabbage grown via insecticide resistance management with two farming methods used by Thai farmers. Background Insecticide usage is currently being reduced by the employment of sustainable products and the promotion of environmentally friendly methods, thereby increasing the income of Chinese cabbage farmers in Thailand. Methods This study aims to evaluate the control of insect pests and marketable produce in Chinese cabbage using various methods. Pests were counted every five days, and the marketable produce was evaluated. Greenhouse gas emissions and environmental impact were estimated using methodologies such as the environmental impact quotient, with the pesticide usage costs and benefit-cost ratios recorded. Results The study compared two farming methods with insecticide resistance management, revealing that in the growing of Chinese cabbage, the latter exhibited lower emissions per acre and kg. However, the environmental impact was higher in methods 1 and 2 due to the increased spray application involved. The insecticide resistance management method was found to effectively control pests and produce marketable produce with less total investment and labour expenses. Conclusion The study analysed the impact of farming practices and pesticide resistance management strategies on the environment and carbon emissions. The results showed that insecticide resistance management is more effective in reducing carbon emissions and positively impacting the environment while also providing a better benefit-cost ratio. However, the study suggests that education and continuous monitoring are required for effective resistance management. The findings also emphasise the need for adaptation to changing pests and the consideration of external factors such as market demand, climate change, and government policies to ensure long-term sustainability.