Insecticide Resistance Research Articles

Patterns of herbicide resistance in Raphanus raphanistrum revealed by comprehensive testing and statistical analysis.

Raphanus raphanistrum causes $40 million total revenue losses annually in Western Australia partly due to its historically-documented ability to evolve herbicide resistance to multiple modes of action. In this study, 376 field-sampled populations of R. raphanistrum were tested for resistance to 21 herbicides applied at the recommended label rate. Eight treatments were herbicide mixtures with two, three or four modes of action. A total of 7199 individual resistance tests were conducted across 4 years by screening approximately 104 000 individual seeds and seedlings. The mean survival of individuals within a population for all standalone herbicides was 9%, whereas survival was significantly decreased to 3.5% with a herbicide mixture. Some herbicides such as triasulfuron (herbicide Group 2), 2,4-D (Group 4) or diflufenican (Group 12) were highly impacted by resistance, with frequencies of resistant populations being > 50%. Conversely, there was negligible resistance to glyphosate (Group 9) or protoporphyrinogen oxidase (PPO) inhibitors (tiafenacil, saflufenacil + trifludimoxazin, fomesafen: Group 14), and pre-emergence herbicides (i.e., atrazine or mesotrione: Groups 5 and 27, respectively) remained largely effective. Binary, ternary or quaternary mixtures of Groups 4, 6, 12 and 27 herbicides reduced the frequency of high-level resistant populations to 7.1%, 3.8% or 0%, respectively. The cost-effective control of R. raphanistrum remains a challenge due to herbicide resistance. Raphanus raphanistrum management relies heavily on herbicide uses not yet compromised by resistance, such as pre-emergence herbicides (atrazine, fomesafen, mesotrione), glyphosate, and mixtures of two, three or four modes of action including bromoxynil, diflufenican, MCPA, picolinafen, pyrasulfotole and topramezone. Strategies that integrate effective herbicide use patterns, novel modes of action and efficiently-mechanized non-chemical weed control options (i.e., seed destructors) can completely constrain the selection of herbicide resistance in this highly adaptable species. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

A rapid and simple micro-assay to assess catalase activity in individual mosquito tissues.

Oxidative stress generated as a normal byproduct of aerobic metabolism is minimized by the enzyme catalase (CAT; EC 1.11.1.6), which reduces hydrogen peroxide to molecular oxygen and water. In various mosquitoes, hydrogen peroxide and/or CAT activity have been implicated in oxidative responses to viral and protozoal pathogens as well as in ovarian maturation and insecticide resistance. We combined features of various CAT assays to develop a simple micro-assay that enables comparison of enzyme activities in individual mosquito tissues on a microscope slide. Activity recovered in the supernatant of mosquito whole body homogenates was inhibited by the CAT-specific inhibitor 3-amino-1,2,4-triazole. Activity was higher in blood-fed mosquitoes, consistent with exogenous enzyme in vertebrate blood. Triton X-100 improved evaluation of dissected organs, and accurate comparisons required careful removal of extraneous tissues. In unfed mosquitoes baseline CAT activity was lower in ovaries than in midgut or fatbody, but increased as oocytes matured after a blood meal, and was detectable in a single mature egg. CAT has unusual kinetics and can be difficult to assay directly. Our observations provide a simple approach for direct evaluation of CAT activity independent of changes in transcript levels and results of RNAi-based interference.

Mosquito species identification accuracy of early deployed algorithms in IDX, a vector identification tool

Mosquito-borne diseases continue to pose a great threat to global public health systems due to increased insecticide resistance and climate change. Accurate vector identification is crucial for effective control, yet it presents significant challenges. IDX - an automated computer vision-based device capable of capturing mosquito images and outputting mosquito species ID has been deployed globally resulting in algorithms currently capable of identifying 53 mosquito species. In this study, we evaluate deployed performance of the IDX mosquito species identification algorithms using data from partners in the Southeastern United States (SE US) and Papua New Guinea (PNG) in 2023 and 2024 . This preliminary assessment indicates continued improvement of the IDX mosquito species identification algorithms over the study period for individual species as well as average regional accuracy with macro average recall improving from 55.3% [Confidence Interval (CI) 48.9, 61.7] to 80.2% [CI 77.3, 84.9] for SE US, and 84.1% [CI 75.1, 93.1] to 93.6% [CI 91.6, 95.6] for PNG using a CI of 90%. This study underscores the importance of algorithm refinement and dataset expansion covering more species and regions to enhance identification systems thereby reducing the workload for human experts, addressing taxonomic expertise gaps, and improving vector control efforts.

How Does Herbicide Resistance Change Farmer’s Weed Management Decisions? Evidence from the Roundup Ready Experiment

Adoption of diverse weed management practices is viewed as essential for slowing the spread of herbicide-resistant (HR) weeds. Yet, adoption of diverse tactics has remained low, while there has been explosive growth of resistant weeds. This study analyzes U.S.-farm-level data to identify factors affecting adoption of diverse weed management practices. This study uses directed acyclic graphs (DAGs) to consider how practice adoption is influenced by different causal pathways between farmer and farm characteristics and farmer awareness of and concern over HR weeds. This study then uses multiple regression analysis to estimate the direct and indirect pathways that influence practice adoption. Respondents relied more heavily on herbicide-based weed control methods than on mechanical or cultural methods. Concern over herbicide resistance increased the number of practices farmers adopted and the percentage of acres where farmers implemented these practices. Practice adoption was negatively associated with increasing levels of farmer risk aversion. Technological optimism—belief that new herbicides would soon be developed to counter HR weeds—discouraged diverse herbicide use practices that combat resistance, but encouraged use of some non-chemical weed control methods. Perceived weed dispersal externalities (from weed mobility) led to more diverse weed management, running counter to hypotheses that greater mobility reduces incentives for individual resistance management.

EFFECT OF SEX AND AGE ON SURVIVAL OF ADULT CULEX TARSALIS FROM A SUSCEPTIBLE LABORATORY STRAIN EXPOSED TO PERMETHRIN IN THE CDC BOTTLE BIOASSAY

ABSTRACT This study investigates the effect of mosquito sex and age on the survival and resistance determination of adult Culex tarsalis exposed to permethrin, a pyrethroid commonly used for mosquito control, using the Centers for Disease Control and Prevention (CDC) bottle bioassay method. A permethrin-susceptible strain of Cx. tarsalis (Bakersfield strain) was used in this study. Survival was compared for young adult females (2–5 days old) relative to older adult females (7–10 days old) and separately for female and male mosquitoes of the same age (2–5 days old). Mortality was slightly higher for males than females during the first observation period (0–5 min) following permethrin exposure, and higher for older females relative to younger females from 5 to 10 min following permethrin exposure, with no differences in mortality by either sex or age for observation periods during the remainder of the diagnostic period. When evaluated over the full diagnostic period, survival varied with mosquito age but not sex. However, all mosquitoes, regardless of sex or age, died within the 30-min diagnostic period for this species, confirming their permethrin susceptibility per the CDC bottle bioassay. This research contributes valuable insight into the potential impact of sex and age on mosquito susceptibility to insecticides in the context of insecticide resistance determination.

A duplication driving metabolic insecticide resistance in Aedes aegypti

A duplication driving metabolic insecticide resistance in Aedes aegypti

A self-eliminating allelic-drive reverses insecticide resistance in Drosophila leaving no transgene in the population

AbstractInsecticide resistance (IR) poses a significant global challenge to public health and welfare. Here, we develop a locally-acting unitary self-eliminating allelic-drive system, inserted into the Drosophila melanogaster yellow (y) locus. The drive cassette encodes both Cas9 and a single gRNA to bias inheritance of the favored wild-type (1014 L) allele over the IR (1014 F) variant of the voltage-gated sodium ion channel (vgsc) target locus. When enduring a fitness cost, this transiently-acting drive can increase the frequency of the wild-type allele to 100%, depending on its seeding ratio, before being eliminated from the population. However, in a fitness-neutral “hover” mode, the drive maintains a constant frequency in the population, completely converting IR alleles to wild-type, even at low initial seeding ratios.

Improved management of Italian ryegrass (Lolium perenne spp. multiflorum) with mixtures of tiafenacil and ACCase or glutamine synthetase inhibitors

Abstract Herbicide-resistant Italian ryegrass [Lolium perenne L. spp. multiflorum (Lam.) Husnot] is a significant problem in multiple cropping systems because of its rapid growth, open pollination, prolific seed production, and multiple cases of resistance worldwide, except to protoporphyrinogen oxidase (PPO) inhibitors. This research evaluated tiafenacil, a new PPO inhibitor, in mixtures with glutamine synthetase or acetyl-CoA carboxylase (ACCase)-inhibiting herbicides to manage resistant L. multiflorum populations. Tiafenacil efficacy against L. multiflorum was growth stage-dependent, with increased efficacy at earlier stages in greenhouse studies. The LD90 was 41.06 g ai ha-1 at BBCH23, and increased to 9.0-fold at BBCH33. Field studies indicated that changes in carrier volume did not affect tiafenacil’s efficacy; the highest tested rate of tiafenacil (75 g ai ha-1) reduced L. multiflorum inflorescence weight by 50-90%. Mixtures of tiafenacil and glufosinate (1,150 g ai ha-1) improved L. multiflorum control (+24-43%) and reduced inflorescence weight (+15-34%), particularly at the highest tested rates (50 and 75 g ai ha-1), suggesting synergistic effects based on Colby’s test. Tiafenacil with ACCase inhibitors improved L. multiflorum control (+19-49%) and inflorescence weight reduction (+8-13%). These mixtures exhibited an additive effect when combined with fluazifop and a synergistic effect with clethodim. Herbicide mixtures and application strategies are critical to effective L. multiflorum management. Tiafenacil, especially when used with glufosinate or ACCase inhibitors, offers an effective solution to L. multiflorum management and is a strategic tool against herbicide resistance, as resistance to PPO inhibitors has not evolved. Further research should assess practices to ensure the long-term viability of these mixtures for resistance management.

Insecticide-impregnated dog collars for the control of visceral leishmaniasis: evaluation of the susceptibility of field Lutzomyia longipalpis populations to deltamethrin.

Visceral leishmaniasis (VL) is a zoonotic disease caused by Leishmania infantum and transmitted by the sand fly Lutzomyia longipalpis. Dogs are the major domestic reservoir of L. infantum. To prevent the spread of the disease, dog collars impregnated with 4% deltamethrin have been effectively used in VL endemic areas. However, this approach may contribute to the emergence of insecticide resistance in sand flies. Therefore, it is important to characterize the susceptibility of different populations of Lu. longipalpis to deltamethrin in areas where insecticide-impregnated dog collars are used. Six field sand fly populations from Brazil were exposed to deltamethrin in CDC bottle bioassays at the diagnostic doses (DD) of 21.9μg/bottle and 30μg/bottle. For the dose-response (DR) experiments, doses of 1, 3, 5, 7, 9 and 11μg/bottle of deltamethrin were used to impregnate bottles; control group bottles were impregnated with acetone only. Each bottle contained an average of 20 sand flies, both male and female, and they were exposed to either deltamethrin or acetone for 60min. Based on the DD of 21.9μg/bottle, three populations were susceptible to deltamethrin. In contrast, two populations collected from the states of Ceará and Minas Gerais exhibited mortality rates of 94.9% and 95.7%, indicating possible resistance, and one population from the state of Ceará showed resistance, with a mortality rate of 87.1%. At the DD of 30μg/bottle, two populations from the states of Ceará and Piauí showed possible resistance, while the other four populations were susceptible. The resistance ratio (RR50) ranged from 2.27 to 0.54, and RR95 ranged from 4.18 to 0.33, indicating a low resistance intensity. This study established a DD for Lu. longipalpis using the CDC bottle bioassay. We found that Lu. longipalpis populations in three Brazilian states where insecticide-impregnated dog collars were used for VL control were susceptible to deltamethrin. However, one population in Ceará State was classified as resistant to deltamethrin. These results contribute to the current knowledge on sand fly resistance and surveillance, and highlight the need for a better understanding of the resistance mechanisms of Lu. longipalpis in areas where insecticide-impregnated dog collars have been widely used.

A novel sustainable biocide against the fruit fly Drosophila suzukii made from orange peels.

Drosophila suzukii (D. suzukii), a pervasive pest originating from Southeast Asia, presents a substantial risk to global agriculture. The ability of the female flies to lay eggs within fruits of varying maturity stages, combined with the accelerated offspring development within warmer climates, results in rapid population growth. This poses significant challenges for fruit production and viticulture, exacerbated by the increasing prevalence of pesticide resistance. We propose a solution to this growing issue using an attract-and-kill approach by making use of upcycled organic waste materials made from orange peels. Specifically, we have tested an innovative salty orange peel product (OPP) in a choice experiment, in which OPP and hydrogel (control) were made available to fruit flies in Petri dishes situated beneath red wine grapes. The number of dead flies in both Petri dishes were counted each day and fly maggots inside berries were extracted after four days. Since Petri dishes were covered with a red lid, flies only selected on the basis of olfactory cues. Our results showed a higher number of captured flies in Petri dishes containing OPP compared to those with the hydrogel control. Furthermore, a notable reduction in the number of maggots was observed inside grapes located above OPP compared to the grapes closer to the hydrogel control. Dilution of OPP was followed by a lower count of dead flies. In additional choice experiments, the concentration of NaCl was found to be positively correlated with the number of dead flies. This suggests an important lethal effect caused by high salt concentrations. In a final experiment, OPP was also compared to the commercially-available attractant called Drosalure™, which resulted in a slightly higher attractiveness of OPP to D. suzukii. These findings suggest that OPP holds potential as a cost-efficient and eco-friendly biocide made from organic waste material. OPP offered in attract-and-kill traps equipped with small entry holes is safe for bees and may replace other less eco-friendly control measures for D. suzukii in organic vineyards.

Insecticide resistance and its intensity in urban Anopheles arabiensis in Kisumu City, Western Kenya: Implications for malaria control in urban areas.

The rise of insecticide resistance poses a growing challenge to the effectiveness of vector control tools, particularly in rural areas. However, the urban setting has received comparatively less focus despite its significance in attracting rural to urban migration. Unplanned urbanization, often overlooked, exacerbates insecticide resistance as Anopheles mosquitoes adapt to the polluted environments of rapidly expanding cities. This study aimed to assess the insecticide susceptibility status of malaria vectors and identify potential underlying mechanisms across three distinct ecological settings characterized by differing levels of urbanization in Kisumu County, Kenya. The study was conducted in 2022-2023 in Kisumu County, western Kenya. Field-derived An. gambiae (s.l.) larvae collected from a long stretch of urban-to-rural continuum were phenotyped as either resistant or susceptible to six different insecticides using the World Health Organization (WHO) susceptibility test. Polymerase chain reaction (PCR) techniques were used to identify the species of the An. gambiae complex and screened for mutations at voltage-gated sodium channels (Vgsc-1014F, Vgsc-1014S, Vgsc-1575Y) and acetylcholinesterase (Ace1) target site mutation 119S. Metabolic enzyme activities (non-specific β-esterases and monooxygenases) were evaluated in mosquitoes not exposed to insecticides using microplate assays. Additionally, during larval sampling, a retrospective questionnaire survey was conducted to determine pesticide usage by the local inhabitants. Anopheles arabiensis dominated in urban (96.2%) and peri-urban (96.8%) areas, while An. gambiae (s.s.) was abundant in rural settings (82.7%). Urban mosquito populations showed high resistance intensity to deltamethrin (Mortality rate: 85.2% at 10x) and suspected resistance to Pirimiphos-methyl and bendiocarb while peri-urban and rural populations exhibited moderate resistance intensity to deltamethrin (mortality rate >98% at 10x). Preexposure of mosquitoes to a synergist piperonyl butoxide (PBO) significantly increased mortality rates: from 40.7% to 88.5% in urban, 51.9% to 90.3% in peri-urban, and 55.4% to 87.6% in rural populations for deltamethrin, and from 41.4% to 78.8% in urban, 43.7% to 90.7% in peri-urban, and 35% to 84.2% in rural populations for permethrin. In contrast, 100% mortality to chlorfenapyr and clothianidin was observed in all the populations tested. The prevalence of L1014F mutation was notably higher in urban An. arabiensis (0.22) unlike the peri-urban (0.11) and rural (0.14) populations while the L1014S mutation was more prevalent in rural An. gambiae (0.93). Additionally, urban An. arabiensis exhibited elevated levels of mixed function oxidases (0.8/mg protein) and non-specific esterases (2.12/mg protein) compared to peri-urban (0.57/mg protein and 1.5/mg protein, respectively) and rural populations (0.6/mg protein and 1.8/mg protein, respectively). Pyrethroids, apart from their use in public health through LLINs, were being highly used for agricultural purposes across all ecological settings (urban 38%, peri-urban 36% and rural 37%) followed by amidine group, with organophosphates, neonicotinoids and carbamates being of secondary importance. These findings show high resistance of An. arabiensis to insecticides commonly used for vector control, linked with increased levels of detoxification enzymes. The observed intensity of resistance underscores the pressing issue of insecticide resistance in urban areas, potentially compromising the effectiveness of vector control measures, especially pyrethroid-treated LLINs. Given the species' unique behavior and ecology compared to An. gambiae, tailored vector control strategies are needed to address this concern in urban settings.

Sensitivity of Southcentral U.S. Johnsongrass Accessions to Selected Herbicides

Abstract New technologies in grain sorghum allow for the use of multiple acetyl CoA carboxylase- (ACCase) or acetolactate synthase- (ALS) inhibiting herbicides for johnsongrass control. With the growing issue of herbicide resistance, producers need to understand which herbicides will successfully control johnsongrass accessions. To determine the efficacy of herbicides recently registered or ones with potential to become available for use in grain sorghum, johnsongrass seeds were collected from 2017 to 2021 in Arkansas, Kansas, Texas, and Oklahoma and were screened for sensitivity to fluazifop, quizalofop, nicosulfuron, and imazamox. Additionally, glyphosate sensitivity was evaluated because of its use before planting or postharvest. Quizalofop resulted in 100% mortality of all johnsongrass accessions. Of the johnsongrass accessions evaluated, 89% were completely controlled with glyphosate. The ALS inhibitors nicosulfuron and imazamox resulted in 100% mortality of all Oklahoma accessions, but failures occurred on samples from other states. One accession from Kansas, 12 from Texas, and eight from Arkansas were found to have reduced sensitivity to nicosulfuron and imazamox. If producers plan to plant grain sorghum in areas with johnsongrass populations, an ACCase-inhibitor herbicide will most likely provide effective control. Imazamox and nicosulfuron, in conjunction with the appropriate trait, can be utilized in areas with sensitive johnsongrass populations or where other sensitive grass species are present.

Response of Palmer Amaranth Accessions in South Carolina to Selected Herbicides

Abstract Palmer amaranth resistant to dicamba, glufosinate, and protoporphyrinogen oxidase inhibitors has been documented in several southern states. With extensive use of these and other herbicides in South Carolina, a survey was initiated in the fall of 2020 and repeated in the fall of 2021 and 2022 to determine the relative response of Palmer amaranth accessions to selected preemergence (PRE) and postemergence (POST) herbicides. A greenhouse screening experiment was conducted where accessions were treated with three PRE (atrazine, s-metolachlor, and isoxaflutole) and six POST (glyphosate, thifensulfuron-methyl, fomesafen, glufosinate, dicamba, 2,4-D) herbicides at the 1× and 2× use rates. Herbicides were applied shortly after planting (PRE) or at the 2 to 4 leaf growth stage (POST). Percent survival was evaluated 5-14 days after application depending on herbicide activity. Sensitivity to atrazine PRE was lower for 49 and 33 accessions out of 115 to atrazine PRE at the 1× and 2× rate, respectively. Most of the accessions (90%) were controlled by isoxaflutole PRE at the 1× rate. Response to S-metolachlor PRE indicated 34% of the Palmer amaranth accessions survived the 1× rate (>60% survival). There were 11 accessions with reduced sensitivity to fomesafen POST; however, these percentages were not different from the 0% survivor group. Glyphosate POST at the 1× rate did not control most accessions (79%). Palmer amaranth response to thifensulfuron-methyl POST varied across the accessions, with only 36 and 28% controlled at the 1× and 2×rate, respectively. All accessions were controlled by 2,4-D, dicamba, or glufosinate POST. Palmer amaranth accessions from this survey exhibited reduced susceptibility to several herbicides commonly used in agronomic crops in South Carolina. Therefore, growers should continue to utilize multiple management tactics to minimize the evolution of herbicide resistance in Palmer amaranth in South Carolina.

Italian Ryegrass Control Using a Capsule Suspension Formulation of S-metolachlor in Fenclorim-treated Wheat

Abstract Italian ryegrass control is one of the most significant limitations in wheat production in the U.S. today. Resistance to Herbicide Resistance Action Committee (HRAC)/Weed Science Society of America (WSSA) Groups 1, 2, and 9 in Arkansas have further complicated postemergence control, while residual herbicides still show effective weed control. One problem is the potential of HRAC/WSSA Group 15 herbicides to injure wheat when applied preemergence, indicating the need for a herbicide safener. A series of experiments were conducted in Fayetteville, AR, to evaluate crop tolerance and Italian ryegrass control using a capsule suspension formulation of S-metolachlor in conjunction with fenclorim-treated wheat. Experiments were conducted as a two-factor factorial with S-metolachlor applied at three rates (0.37, 0.74, and 1.12 kg ai ha-1) and a microencapsulated formulation of acetochlor at 1.05 kg ai ha-1, and three rates of a fenclorim seed treatment at 0, 0.5, and 2.0 g ai kg-1 of seed. Separate experiments utilized either a preemergence (PRE) or a delayed-preemergence (DPRE) application timing. In both experiments, S-metolachlor at 0.74 and 1.12 kg ai ha-1 provided 77 to 96% control of Italian ryegrass by preharvest, whereas acetochlor only provided 49 to 72% control. Visible wheat injury from PRE applications ranged from 7 to 49% for all treatments 21 d after treatment (DAT), with a reduction in injury when fenclorim-treated wheat was used for both the 0.74 and 1.12 kg ai ha-1 rate of S-metolachlor. In the DPRE experiments, wheat injury ranged from 5 to 16% 21 DAT with no noticeable safening from the presence of fenclorim at any herbicide rate. The results of these experiments indicate that a DPRE application using a CS formulation of S-metolachlor would be more favorable for producers to mitigate the potential for injury to wheat while providing Italian ryegrass control. Additionally, at the DPRE application timing, fenclorim is unnecessary for S-metolachlor to be safely applied at the rates evaluated.

Axant™ Flex cotton response to topramezone applied early- or mid-postemergence

Abstract The continued development of herbicide-resistant weeds, such as Palmer amaranth, represents a growing concern across the United States Cotton Belt. To mitigate this issue, BASF Corporation developed Axant™ Flex cotton, the first quadruple-stacked herbicide resistance germplasm to improve the control of troublesome weed species in cotton. Field studies were conducted in 2022 and 2023 at the Texas Tech University Research Farm near New Deal, TX, to evaluate the response of Axant Flex cotton to topramezone applied alone or in combinations when applied to 3-leaf cotton (early-postemergence (EPOST)) or to 7-leaf cotton (mid-postemergence (MPOST)). No difference in cotton stand was observed between isoxaflutole or prometryn PRE treatments compared to the nontreated control. In 2022, no EPOST treatment caused greater than 6% crop response at 7 and 14 d after application (DAA). When treatments were made to 7-leaf cotton, crop response did not exceed 18% at 7 and 14 DAA. In 2023, crop response was ≤ 2% at 28 DAA regardless of application timing. No differences in lint yield were observed following any herbicide treatment when compared to the nontreated control in either year. Additionally, fiber length and strength were not adversely affected by treatments containing topramezone EPOST or MPOST in 2022 and 2023. These results support the potential use of topramezone in Axant Flex cotton to help manage troublesome weeds without detrimental effects on yield and fiber quality.

Multiple herbicide resistance among kochia (Bassia scoparia) populations in southcentral Great Plains

Abstract Multiple herbicide-resistant (MHR) kochia [Bassia scoparia (L.) A. J. Scott] is a concern for farmers in the Great Plains. A total of 82 B. scoparia populations were collected from western Kansas (KS), western Oklahoma (OK), and High Plains of Texas (TX) during fall of 2018 and 2019 (from the various locations), and their herbicide resistance status was evaluated. The main objectives were to (1) determine the distribution and frequency of resistance to atrazine, chlorsulfuron, dicamba, fluroxypyr, and glyphosate; and (2) characterize the resistance levels to glyphosate, dicamba, and/or fluroxypyr in selected B. scoparia populations. Results indicated that 33, 100, 48, 30, and 70% of the tested B. scoparia populations were potentially resistant (≥20% survival frequency) to atrazine, chlorsulfuron, dicamba, fluroxypyr, and glyphosate, respectively. A three-way premixture of dichlorprop/dicamba/2,4-D provided 100% control of all the tested populations. Dose-response studies further revealed that KS-9 and KS-14 B. scoparia populations from KS were 5- to 10-fold resistant to dicamba, 3- to 6-fold resistant to fluroxypyr, and 4- to 5-fold resistant to glyphosate as compared to the susceptible (KS-SUS) population. Similarly, OK-10 and OK-11 populations from OK were 10- to 13-fold resistant to dicamba, 3- to 4-fold resistant to fluroxypyr and glyphosate compared to the OK-SUS population. TX-1 and TX-13 B. scoparia populations from TX were 2- to 4-fold resistant to dicamba and TX-1 was 5-fold resistant to glyphosate compared to the TX-SUS population. These results confirm the first report of dicamba and fluroxypyr-resistant B. scoparia from Oklahoma, and glyphosate and dicamba-resistant B. scoparia from TX. These results imply that adopting effective integrated weed management strategies (chemical and non-chemical) is required to mitigate the further spread of MHR B. scoparia in the region.

Influence of Inert Minerals and Botanicals on Adult Emergence of Pulse Beetle, Callosobruchus maculatus (Fabricius), in Stored Blackgram

Background: Pulses hold significant global importance as a food source, with the pulse beetle, Callosobruchus maculatus, being a major pest affecting them. As consumer preferences shift towards insecticide residue-free food, pest management strategies are adapting. Inert minerals and botanicals offer a promising solution to address concerns about insecticide safety, resistance development, and regulatory standards. Hence, this study seeks to assess how these substances impact the emergence of C. maculatus adults. Methods: One kilogram of blackgram was taken in three replications and treated with inert minerals and botanicals. In each container, ten pairs of newly emerged adult beetles were introduced. A subsample of 50 g was taken in small plastic jars to record, the day when the first adult beetle emerged, the daily count of adult beetles, and the overall count of emerged adult beetles. Result: The research showed no significant difference between treatments and untreated control w.r.t day of first adult emergence of C. maculatus. The percentage of adult emergence of C. maculatus in blackgram seeds treated with diatomaceous earth was 21.06% which was significantly the lowest value when compared to untreated control (86.03%). The total count of emerged adult beetles from the main sample was less in diatomaceous earth (135.33 adults) against untreated control (751.67 adults). Among all the treatments tested, diatomaceous earth performed better in controlling the adult emergence of C. maculatus.

Characterization of two glutathione S-transferase genes involved in clothianidin resistance in Bradysia odoriphaga.

Glutathione S-transferase (GST) is a key phase II detoxification enzyme involved in xenobiotics metabolism, and plays a pivotal role in the evolution of resistance to various types of insecticides. However, the specific functions of GST genes in clothianidin resistance remain obscure in Bradysia odoriphaga. Here, a specific GST inhibitor, diethyl maleate (DEM), significantly increased the mortality of Bradysia odoriphaga larvae following exposure to clothianidin, and the activity of GST enzyme in clothianidin-resistant (CL-R) strain of Bradysia odoriphaga was markedly greater than that in the SS strain. Two sigma BoGSTs (BoGSTs1 and BoGSTs2) were markedly overexpressed in the CL-R strain and exhibited a higher abundance in the Malpighian tubules or midgut. Exposure to clothianidin resulted in a significant increased expression of BoGSTs1 and BoGSTs2. The knockdown of BoGSTs1 and BoGSTs2 increased sensitivity of larvae to clothianidin in the resistant strain. Furthermore, overexpression of BoGSTs1 and BoGSTs2 led to a significant increase in Escherichia coli cells tolerance to clothianidin. In vitro metabolic assays indicate that these two GSTs cannot directly metabolize clothianidin and its secondary metabolite desmethyl-clothianidin. Disk diffusion assays and fluorescence competitive binding assays indicated that BoGSTs1 and BoGSTs2 play a critical role in clothianidin resistance by antioxidant activity and non-catalytic binding activity. The docking results showed that BoGSTs1 and BoGSTs2 have strong binding affinity toward clothianidin. Collectively, these findings pinpoint the potential role of BoGSTs1 and BoGSTs2 in conferring insecticide resistance in Bradysia odoriphaga and contribute to our understanding of the underlying mechanisms of insecticide resistance. © 2024 Society of Chemical Industry.

The LTAR Cropland Common Experiment at R. J. Cook Agronomy Farm.

Dryland agriculture in the Inland Pacific Northwest is challenged in part by rising input costs for seed, fertilizer, and agrichemicals; threats to water quality and soil health, including soil erosion, organic matter decline, acidification, compaction, and nutrient imbalances; lack of cropping system diversity; herbicide resistance; and air quality concerns from atmospheric emissions of particulate matter and greenhouse gases. Technological advances such as rapid data acquisition, artificial intelligence, cloud computing, and robotics have helped fuel innovation and discovery but have also further complicated agricultural decision-making and research. Meeting these challenges has promoted interest in (1) supporting long-term research that enables assessment of ecosystem service trade-offs and advances sustainable and regenerative approaches to agriculture, and (2) developing coproduction research approaches that actively engage decision-makers and accelerate innovation. The R. J. Cook Agronomy Farm (CAF) Long-Term Agroecosystem Research (LTAR) site established a cropping systems experiment in 2017 that contrasts prevailing (PRV) and alternative (ALT) practices at field scales over a proposed 30-year time frame. The experimental site is on the Washington State University CAF near Pullman, WA. Cropping practices include a wheat-based cropping system with wheat (Triticum aestivum L.), canola (Brassica napus, variety napus), chickpea (Cicer arietinum), and winter pea (Pisum sativum), with winter wheat produced every third year under the ALT practices of continuous no-tillage and precision applied N, compared to the PRV practice of reduced tillage (RT) and uniformly applied agrichemicals. Biophysical measurements are made at georeferenced locations that capture field-scale spatial variability at temporal intervals that follow approved methods for each agronomic and environmental metric. Research to date is assessing spatial and temporal variations in cropping system performance (e.g., crop yield, soil health, and water and air quality) for ALT versus PRV and associated tradeoffs. Future research will explore a coproduction approach with the intent of advancing discovery, innovation, and impact through collaborative stakeholder-researcher partnerships that direct and implement research priorities.

Societal uses of the main water bodies inhabited by malaria vectors and implications for larval source management

BackgroundLarval source management (LSM) effectively reduces mosquito populations at their breeding sites, addressing issues like insecticide resistance that limit the effectiveness of primary interventions such as insecticide-treated nets (ITNs). Although traditionally used in urban and dry areas, recent research suggests it might also be effective in rural settings in eastern and southern Africa, where Anopheles funestus thrives in permanent water bodies that sustain year-round transmission. Targeting these habitats could enhance LSM, but it requires understanding local community practices, as mosquito breeding sites often overlap with community water resources. This study examined how communities use aquatic habitats and how these practices may impact LSM strategies, with a focus on habitats used by An. funestus.MethodsThis study was conducted in three villages in the Ulanga and Malinyi districts of southeastern Tanzania using a mixed-methods approach. Quantitative data were collected through cross-sectional surveillance, and qualitative data through unstructured interviews, focus group discussions, and field observations. Data analysis integrated both quantitative and qualitative findings to develop a comprehensive understanding of community perspectives.ResultsA survey of 931 aquatic habitats found mosquito larvae in 73% of them, with late instar An. funestus present in 23%. River streams made up 41% of the habitats, while ground pools accounted for 4%. Most habitats (90%) were used by communities, including 95% of those with An. funestus larvae, for activities such as domestic chores, agriculture, livestock rearing, brickmaking, and fishing. Focus group discussions revealed a willingness to adopt LSM, with a preference for larviciding and habitat modification over habitat removal, as the water sources were vital for daily use. Community concerns centered on the safety of larvicides for humans and animals, the environmental impact, and the need for better awareness of how LSM affects health and livelihoods.ConclusionThis study highlights community perspectives on LSM, focusing on the dual function of aquatic habitats as mosquito breeding sites and essential community water sources. This dual role presents both challenges and opportunities, suggesting that LSM strategies must balance public health needs with socio-economic realities. There was a clear preference for larviciding and habitat modification over removal, with a strong emphasis on health and environmental safety. The study emphasizes the importance of educating communities on the safety and effectiveness of LSM, and tailoring LSM strategies to fit the needs and preferences of local communities.