Evolutionary rescue in resistance to pesticides.

Evolutionary rescue occurs when the genetic evolution of adaptation saves a population from decline or extinction after environmental change. The evolution of resistance to pesticides is a special scenario of abrupt environmental change, where rescue occurs under (very) strong selection for one or a few de novo resistance mutations of large effect. Here, a population genetic model of evolutionary rescue with density-dependent population change is developed, with a focus on deriving results that are important to resistance management. Massive stochastic simulations are used to generate observations, which are accurately predicted using analytical approximations. Key results include the probability density function for the time to resistance and the probability of population extinction. The distribution of resistance times shows a lag period, a narrow peak and a long tail. Surprisingly, the mean time to resistance can increase with the strength of selection because, if a mutation does not occur early on, then its emergence is delayed by the pesticide reducing the population size. The probability of population extinction shows a sharp transition, in that when extinction is possible, it is also highly likely. Consequently, population suppression and (local) eradication can be theoretically achievable goals, as novel strategies to delay resistance evolution.

Mapping cryptic binding sites of drug targets to overcome drug resistance.

The emergence of drug resistance is a primary obstacle for successful chemotherapy. Drugs that target cryptic binding sites (CBSs) represent a novel strategy for overcoming drug resistance. In this short communication, we explain and discuss how the discovery of CBSs and their inhibitors can overcome drug resistance.

Reduced proinsecticide activation by cytochrome P450 confers coumaphos resistance in the major bee parasite Varroa destructor.

Varroa destructor is one of the main problems in modern beekeeping. Highly selective acaricides with low toxicity to bees are used internationally to control this mite. One of the key acaricides is the organophosphorus (OP) proinsecticide coumaphos, that becomes toxic after enzymatic activation inside Varroa We show here that mites from the island Andros (AN-CR) exhibit high levels of coumaphos resistance. Resistance is not mediated by decreased coumaphos uptake, target-site resistance, or increased detoxification. Reduced proinsecticide activation by a cytochrome P450 enzyme was the main resistance mechanism, a powerful and rarely encountered evolutionary solution to insecticide selection pressure. After treatment with sublethal doses of [14C] coumaphos, susceptible mite extracts had substantial amounts of coroxon, the activated metabolite of coumaphos, while resistant mites had only trace amounts. This indicates a suppression of the P450 (CYP)-mediated activation step in the AN-CR mites. Bioassays with coroxon to bypass the activation step showed that resistance was dramatically reduced. There are 26 CYPs present in the V. destructor genome. Transcriptome analysis revealed overexpression in resistant mites of CYP4DP24 and underexpression of CYP3012A6 and CYP4EP4 RNA interference of CYP4EP4 in the susceptible population, to mimic underexpression seen in the resistant mites, prevented coumaphos activation and decreased coumaphos toxicity.

Mode of inheritance for pesticide resistance, importance and prevalence: A review.

Pesticides remain a cornerstone in pest control, yet their extensive and irrational use also fuel the evolution of resistance. This review analyzes globally published experimental data spanning from the 1970s to 2023 to focus on how phenotypic and underlying genotypic variations are shaped during the selective response. The discussion commences with an examination of sex-linked/maternal resistance. Observations related to maternal inheritance have enriched our understanding of pesticide mode of action, notably exemplified by bifenazate. However, the predominant control of the resistant phenotype is attributed to autosomal traits, with a high prevalence of dominance and monogenic inheritance observed, also evident in field strains. This observation raises concerns regarding resistance management strategies due to their potential to accelerate the spread of resistance. The interplay between dominance levels and monogenic inheritance is further explored, with dominant traits being significantly more prevalent in polygenic inheritance. This observation may be attributed to the accumulation of enhanced metabolism. Notably, further analysis indicated that field strains exhibit a higher incidence of monogenic inheritance compared to other selected strains, aligning with established theoretical frameworks. In conclusion, the genetic architecture of resistance warrants increased research focus for its pivotal role in guiding resistance management strategies and advancing fundamental research.

Comparative fitness of Monilinia fructicola isolates with multiple fungicide-resistant phenotypes.

This study characterized 52 isolates of Monilinia fructicola from peach and nectarine orchards for their multi-resistance patterns to thiophanate-methyl (TF), tebuconazole (TEB), and azoxystrobin (AZO) using in vitro sensitivity assays and molecular analysis. The radial growth of M. fructicola isolates was measured on media amended with a single discriminatory dose of 1 µg/ml for TF and AZO and 0.3 µg/ml for TEB. Cyt b, CYP51, and ß-tubulin were tested for point mutations that confer resistance to quinone outside inhibitors (QoIs), demethylation inhibitors (DMIs), and methyl benzimidazole carbamates (MBCs), respectively. Eight phenotypes were identified including isolates with single, double, and triple in vitro resistance to QoI, MBC, and DMI fungicides. All resistant phenotypes to TF and TEB presented the H6Y mutation in ß-tubulin and the G641S mutation in CYP51. None of the point mutations typically linked to QoI resistance were present in the Monilinia isolates examined. Moreover, fitness of the M. fructicola phenotypes was examined in vitro and detached fruit assays. Phenotypes with single-resistance displayed equal fitness in in vitro and fruit assays compared to the wild-type. In contrast, the dual and triple-resistance phenotypes suffered fitness penalties based on osmotic sensitivity and aggressiveness on peach fruit. In this study, multiple resistance to MBC, DMI, and QoI fungicide groups was confirmed in M. fructicola. Results suggest that Monilinia populations with multiple resistance phenotypes are likely to be less competitive in the field than those with single resistance, thereby impeding their establishment over time and facilitating disease management.

Development and implementation of a novel CAPS assay reveals high prevalence of a boscalid resistance marker and its co-occurrence with an azole resistance marker in Erysiphe necator.

Succinate dehydrogenase inhibitors (SDHIs), are frequently used against powdery mildew (PM) fungi, such as Erysiphe necator, the causal agent of grapevine PM. Fungicide resistance, however, hinders effective control. DNA-based monitoring facilitates the recognition of resistance. We aimed (i) to adapt an effective method to detect a widespread genetic marker of resistance to boscalid, a commonly used SDHI, and (ii) to study the co-occurrence of the marker with a marker of resistance to demethylase inhibitor (DMI) fungicides. Sequencing of the sdhB gene identified a non-synonymous substitution, denoted as sdhB-A794G, leading to an amino acid change (H242R) in the sdhB protein. In vitro fungicide resistance tests showed that E. necator isolates carrying sdhB-A794G were resistant to boscalid. We adopted a cleaved amplified polymorphic sequence-based method and screened more than 500 field samples collected from five Hungarian wine regions in two consecutive years. The sdhB-A794G marker was detected in all wine regions and in both years, altogether in 61.7% of samples, including 20.5% in which both sdhB-A794G and the wild-type were present. The frequency of sdhB-A794G was higher in SDHI-treated vineyards than in vineyards without any SDHI application. A significant difference in the presence of the marker was detected among wine regions; its prevalence ranged from none to 100%. We identified significant co-occurrence of sdhB-A794G with the CYP51-A495T (Y136F) mutation of the CYP51 gene, a known marker of resistance to DMIs. The monitoring of fungicide resistance is fundamental for the successful control of E. necator. Our rapid, cost-effective diagnostic method will support decision-making and fungicide resistance monitoring and management.

Management of Insect Pests with Bt Crops in the United States.

Genetically engineered corn and cotton that produce insecticidal toxins derived from the bacterium Bacillus thuringiensis (Bt) have been used to manage insect pests in the United States and elsewhere. In some cases, this has led to regional suppression of pest populations and pest eradication within the United States, and these outcomes were associated with reductions in conventional insecticides and increased profits for farmers. In other instances, pests evolved resistance to multiple Bt traits, compromising the capacity of Bt crops to manage pests and leading to increased feeding injury to crops in the field. Several aspects of pest biology and pest-crop interactions were associated with cases where pests remained susceptible versus instances where pests evolved resistance. The viability of future transgenic traits can be improved by learning from these past outcomes. In particular, efforts should be made to delay resistance by increasing the prevalence of refuges and using integrated pest management.

Decolonizing drug-resistant E. coli with phage and probiotics: breaking the frequency-dependent dominance of residents.

Widespread antibiotic resistance in commensal bacteria creates a persistent challenge for human health. Resident drug-resistant microbes can prevent clinical interventions, colonize wounds post-surgery, pass resistance traits to pathogens or move to more harmful niches following routine interventions such as catheterization. Accelerating the removal of resistant bacteria or actively decolonizing particular lineages from hosts could therefore have a number of long-term benefits. However, removing resident bacteria via competition with probiotics, for example, poses a number of ecological challenges. Resident microbes are likely to have physiological and numerical advantages and competition based on bacteriocins or other secreted antagonists is expected to give advantages to the dominant partner, via positive frequency dependence. Since a narrow range of Escherichia coli genotypes (primarily those belonging to the clonal group ST131) cause a significant proportion of multidrug-resistant infections, this group presents a promising target for decolonization with bacteriophage, as narrow-host-range viral predation could lead to selective removal of particular genotypes. In this study we tested how a combination of an ST131-specific phage and competition from the well-known probiotic E. coli Nissle strain could displace E. coli ST131 under aerobic and anaerobic growth conditions in vitro. We showed that the addition of phage was able to break the frequency-dependent advantage of a numerically dominant ST131 isolate. Moreover, the addition of competing E. coli Nissle could improve the ability of phage to suppress ST131 by two orders of magnitude. Low-cost phage resistance evolved readily in these experiments and was not inhibited by the presence of a probiotic competitor. Nevertheless, combinations of phage and probiotic produced stable long-term suppression of ST131 over multiple transfers and under both aerobic and anaerobic growth conditions. Combinations of phage and probiotic therefore have real potential for accelerating the removal of drug-resistant commensal targets.

Optimization of long-lasting insecticidal bed nets for resistance management: a modelling study and user-friendly app.

BACKGROUND: Up until the present, pyrethroid-treated bed nets have been a key tool for vector control in the fight against malaria. A global system that sets standards and facilitates procurement has successfully driven down the price of these bed nets to enable more of them to be distributed. As a result of their mass rollout, malaria cases have been significantly reduced, but pyrethroid resistance is now widespread. Going forward, new insecticides have been and continue to be developed for use on bed nets, but it is unclear how to best deploy them for maximum impact. METHODS: Here, an app for the optimization of bed nets based on their insecticide loading concentration and deployment lifespan is presented. Underlying the app are simple models that incorporate the chemical and physical properties of bed nets, and the genetic and ecological properties of resistance evolution in mosquitoes. Where possible, default parameter values are fitted from experimental data. The app numerically searches across a massive number of these simple models with variable loading and lifespan to find their optima under different criteria that constrain the options for vector control. RESULTS: The app is not intended to provide a definite answer about the best bed net design, but allows for the quantative exploration of trade-offs and constraints under different conditions. Here, results for the deployment of a new insecticide are explored under default parameter values across public health budgets for the purchase of bed nets. Optimization can lead to substantial gains in the average control of the mosquito population, and these gains are comparatively greater with lower budgets. Whilst optimizing a bed net within the constraints of the incentives of the existing system of standards and procurement leads to substantially greater control than not optimizing the bed net, optimizing the bed net without constraints leads to yet substantially greater control. The most important factor in this optimization is coverage, which depends on the price per bed net. With this in mind, it is unsurprising that the optimization for plausible budgets suggests that a pyrethroid would be the preferred partner for a new insecticide under current constraints because it is cost-effective in the balance of being less expensive than the new insecticide but also less effective due to pre-existing resistance. Surprisingly, a pyrethroid is shown to be an effective partner for a new insecticide in this model because of its contribution to resistance management in delaying the onset of resistance to the new insecticide. CONCLUSIONS: This study highlights the importance of trade-offs in the design of bed nets for vector control. Further, it suggests that there are challenges in the roll-out of bed nets with new insecticides because of the constraints imposed by the global system of standards and procurement, which currently fails to adequately incentivize important considerations in bed net design like resistance management.

Fungicide Resistance: Progress in Understanding Mechanism, Monitoring, and Management.

Fungicide treatments are often essential for maintaining healthy crops and to achieve reliable and high-quality yields. However, continued use of fungicides with the same modes of action can lead to development of fungicide resistance, which has emerged in various plant pathogens and is a serious threat to effective crop protection. Exploration of resistance mechanisms is critical for resistance monitoring and management. This brief review summarizes advances during the past five decades in understanding the molecular resistance mechanisms of plant pathogenic fungi and oomycetes to major classes of fungicides, including benzimidazoles, myosin inhibitors, sterol demethylation inhibitors, quinone outside inhibitors, succinate dehydrogenase inhibitors, anilinopyrimidines, carboxylic acid amides, and oxysterol-binding protein homolog inhibitors. Based on known resistance mechanisms, PCR- and loop-mediated isothermal amplification-based approaches have been developed to allow high-throughput monitoring and early/rapid detection of emerging resistance. Classical principles in fungicide resistance management are also summarized, including using different modes of action of fungicides, limiting the number of applications of the chemicals with site-specific modes of action, and avoidance of their eradicant use. Future studies on novel strategies of disease management, including development of epigenetics- and RNA-based fungicides, will provide valuable knowledge for management of fungicide resistance.

Evidence-based insecticide resistance in South American tomato leaf miner, Phthorimaea absoluta (Meyrick) under laboratory selection.

The South American tomato moth, Phthorimaea absoluta (Meyrick), is one of the key pests of tomato in India. Since its report in 2014, chemical control has been the main means of tackling this pest, both in the open field and protected cultivation. Despite regular insecticidal sprays, many outbreaks were reported from major tomato-growing regions of South India during 2019-2020. A study was conducted to investigate the effect of insecticide resistance on biology, biochemical enzymes, and gene expression in various P. absoluta field populations viz., Bangalore, Kolar, Madurai, Salem, and Anantapur to commonly used insecticides such as flubendiamide, cyantraniliprole, and indoxacarb. Increased levels of insecticide resistance ratios (RR) were recorded in P. absoluta populations of different locations. A significant increase in cytochrome P450 monooxygenase (CYP/MFO) and esterase levels was noticed in the resistant population compared to susceptible one. Through molecular studies, we identified four new CYP genes viz., CYP248f (flubendiamide), CYP272c, CYP724c (cyantraniliprole), and CYP648i (indoxacarb). The expression levels of these genes significantly increased as the folds of resistance increased from G1 to G20 (generation), indicating involvement of the identified genes in insecticide resistance development in P. absoluta. In addition, the resistant populations showed decreased fecundity, increased larval development period, and adult longevity, resulting in more crop damage. The information generated in the present study thus helps in understanding the development of insecticide resistance by P. absoluta and suggests the farmers and researchers to use insecticides wisely by adopting insecticide resistance management as a strategy under integrated pest management.

Crop rotation mitigates impacts of corn rootworm resistance to transgenic Bt corn.

Transgenic crops that produce insecticidal proteins from Bacillus thuringiensis (Bt) can suppress pests and reduce insecticide sprays, but their efficacy is reduced when pests evolve resistance. Although farmers plant refuges of non-Bt host plants to delay pest resistance, this tactic has not been sufficient against the western corn rootworm, Diabrotica virgifera virgifera In the United States, some populations of this devastating pest have rapidly evolved practical resistance to Cry3 toxins and Cry34/35Ab, the only Bt toxins in commercially available corn that kill rootworms. Here, we analyzed data from 2011 to 2016 on Bt corn fields producing Cry3Bb alone that were severely damaged by this pest in 25 crop-reporting districts of Illinois, Iowa, and Minnesota. The annual mean frequency of these problem fields was 29 fields (range 7 to 70) per million acres of Cry3Bb corn in 2011 to 2013, with a cost of $163 to $227 per damaged acre. The frequency of problem fields declined by 92% in 2014 to 2016 relative to 2011 to 2013 and was negatively associated with rotation of corn with soybean. The effectiveness of corn rotation for mitigating Bt resistance problems did not differ significantly between crop-reporting districts with versus without prevalent rotation-resistant rootworm populations. In some analyses, the frequency of problem fields was positively associated with planting of Cry3 corn and negatively associated with planting of Bt corn producing both a Cry3 toxin and Cry34/35Ab. The results highlight the central role of crop rotation for mitigating impacts of D. v. virgifera resistance to Bt corn.

Evaluating insecticide resistance across African districts to aid malaria control decisions.

Malaria vector control may be compromised by resistance to insecticides in vector populations. Actions to mitigate against resistance rely on surveillance using standard susceptibility tests, but there are large gaps in the monitoring data across Africa. Using a published geostatistical ensemble model, we have generated maps that bridge these gaps and consider the likelihood that resistance exceeds recommended thresholds. Our results show that this model provides more accurate next-year predictions than two simpler approaches. We have used the model to generate district-level maps for the probability that pyrethroid resistance in Anopheles gambiae s.l. exceeds the World Health Organization thresholds for susceptibility and confirmed resistance. In addition, we have mapped the three criteria for the deployment of piperonyl butoxide-treated nets that mitigate against the effects of metabolic resistance to pyrethroids. This includes a critical review of the evidence for presence of cytochrome P450-mediated metabolic resistance mechanisms across Africa. The maps for pyrethroid resistance are available on the IR Mapper website, where they can be viewed alongside the latest survey data.

Would You Like Wood or Plastic? Bin Material, Sanitation Treatments, and Bin Inoculum Levels Impact Blue Mold Decay of Stored Apple Fruit.

Blue mold, caused primarily by Penicillium expansum, is a significant postharvest disease of apples. It not only causes economic losses but also produces mycotoxins that contaminate processed fruit products, which contributes to food waste and loss. Previous research has shown that packing and storage bins harbor Penicillium spores and that steam and hot water efficiently reduce spore inoculum levels. However, studies using wooden and plastic bins regarding their ability to harbor spores, the effect of chemical sanitation treatments on spore levels, and the impact of rinsate from treated bins on apple fruit decay have not been investigated for the Mid-Atlantic area (Okull et al. 2006; Rosenberger 2009). We evaluated different sanitation treatments (chemical and physical) to reduce P. expansum inoculum levels on wooden and plastic bins. We determined that wooden bins bound P. expansum spores four orders of magnitude higher than plastic. When both bin types were treated with steam (wooden) or sterile hot water (plastic), Thyme Guard, or Academy, all treatments resulted in significantly (P < 0.05) lower spore levels compared to untreated controls. Although, plastic bins retained lower numbers of spores after inoculation with contaminated spore rinsate and required much higher concentrations of P. expansum spores in rinsate to retain spores at levels that would lead to decay on apple fruit. Overall, we demonstrated that plastic bins retain fewer spores than wooden bins and that both can be sanitized by various physical or chemical treatments. We envision that our findings will be applicable in the future as the techniques implemented in this study were used to investigate industry-relevant questions. Our goal is that the research techniques and findings become feasible with advancements in technology and/or accompany other shifts in existing processes in commercial pome fruit packing and storage facilities.

Field Evaluation of Fungicides for the Management of Neofabraea Leaf Lesion of Olive in California.

Field experiments were conducted during the fall-winter seasons of 2017 to 2018 and 2018 to 2019 to evaluate the efficacy of various fungicides to control Neofabraea leaf lesion of olive. Field trials were conducted in the highly susceptible cultivar Arbosana in a commercial, super-high-density orchard in San Joaquin County, California. Up to eight fungicidal products were applied using an air blast backpack sprayer, and their efficacy was compared with different application strategies. Results showed that most products were effective in reducing infection by the pathogens and limiting disease severity. Overall, best disease control was achieved by thiophanate-methyl, cyprodinil, difenoconazole + cyprodinil, and chlorothalonil, providing up to 75% reduction in disease severity. Copper hydroxide did not control the disease. In 2018 to 2019, the fungicides difenoconazole + cyprodinil and ziram were evaluated in additional field trials using different application strategies (single, dual, and combined applications) suitable for pathogen resistance management. Results showed that both products provided significant reduction in disease severity (∼50%), although no differences in efficacy were found between the two products nor between the different application strategies. Both products performed equally using one or two applications at 2-week intervals following harvest.

Insecticide Resistance and Its Management in Two Invasive Cryptic Species of Bemisia tabaci in China.

The sweet potato whitefly Bemisia tabaci is a major agricultural pest with a wide host range throughout the world. The species designation for B. tabaci includes numerous distinct cryptic species or biotypes. Two invasive B. tabaci biotypes, MEAM1 (B) and MED (Q), were found in China at the end of the 20th century and at the beginning of the 21st century. MEAM1 (B) and MED (Q) show higher pesticide resistance levels than native strains, and the levels of resistance vary with changes in insecticide selection pressure. Recent studies have revealed metabolic resistance mechanisms and target site mutations in invasive B. tabaci strains that render them resistant to a range of insecticides and have uncovered the frequency of these resistance-related mutations in B. tabaci populations in China. Novel pest control agents, such as RNA-based pesticides and nano-pesticides, have achieved effective control effects in the laboratory and are expected to be applied for field control of B. tabaci in the future. In this review, we discuss the mechanisms of resistance developed by these invasive B. tabaci populations since their invasion into China. We also provide suggestions for ecologically sound and efficient B. tabaci control.

Predicting resistance management skill from psychotherapy experience, intellectual humility and emotion regulation.

OBJECTIVE: Resistance management in psychotherapy remains a foundational skill that is associated with positive client outcomes (Westra, H. A., & Norouzian, N. (2018). Using motivational interviewing to manage process markers of ambivalence and resistance in cognitive behavioral therapy. Cognitive Therapy and Research, 42(2), 193-203). However, little is known about which therapist characteristics contribute to successful management of resistance. Research has suggested that psychotherapy performance does not improve with experience (Goldberg, S. B., Rousmaniere, T., Miller, S. D., Whipple, J., Nielsen, S. L., Hoyt, W. T., & Wampold, B. E. (2016). Do psychotherapists improve with time and experience? A longitudinal analysis of outcomes in a clinical setting. Journal of Counseling Psychology, 63(1), 1-11), that psychotherapists lack humility (Macdonald, J., & Mellor-Clark, J. (2015). Correcting psychotherapists' blindsidedness: Formal feedback as a means of overcoming the natural limitations of therapists. Clinical Psychology & Psychotherapy, 22(3), 249-257), and that difficult therapeutic moments may dysregulate therapist emotions (Muran, J. C., & Eubanks, C. F. (2020). Therapist performance under pressure: Negotiating emotion, difference, and rupture. American Psychological Association). This study aimed to 1) identify whether psychotherapy experience (i.e., training versus no training and number of years of psychotherapy experience) was associated with resistance management skill, and 2) identify whether humility and difficulties regulating emotions among trained individuals were each associated with resistance management. METHOD: A sample of 76 trained and 98 untrained participants were recruited for the present study. All participants completed the Comprehensive Intellectual Humility Scale (CIHS, Krumrei-Mancuso, E. J., & Rouse, S. V. (2016). The development and validation of the comprehensive intellectual humility scale. Journal of Personality Assessment, 98(2), 209-221), the Difficulties in Emotion Regulation Scale (DERS; Gratz, K. L., & Roemer, L. (2004). Multidimensional assessment of emotion regulation and dysregulation: Development, factor structure, and initial validation of the difficulties in emotion regulation scale. Journal of Psychopathology and Behavioral Assessment, 26(1), 41-54), and the Resistance Vignette Task (RVT; Westra, H. A., Nourazian, N., Poulin, L., Hara, K., Coyne, A., Constantino, M. J., Olson, D., & Antony, M. M. (2021). Testing a deliberate practice workshop for developing appropriate responsivity to resistance markers: A randomized clinical trial. Psychotherapy, 58, 175-185 ) which was used to assess resistance management skill. RESULTS: Trained individuals performed significantly better on resistance management than untrained individuals; however, years of experience within the trained sample were not associated with resistance management. Conversely, lower humility and greater difficulties regulating emotions were each associated with significantly poorer resistance management in trained individuals. CONCLUSION: These findings suggest the possibility of improving training to focus on key skills, like resistance management, through supporting humility and emotion regulation in training, as opposed to simply acquiring more experience.

Self-limiting fall armyworm: a new approach in development for sustainable crop protection and resistance management.

BACKGROUND: The fall armyworm, Spodoptera frugiperda, is a significant and widespread pest of maize, sorghum, rice, and other economically important crops. Successful management of this caterpillar pest has historically relied upon application of synthetic insecticides and through cultivation of genetically engineered crops expressing insecticidal proteins (Bt crops). Fall armyworm has, however, developed resistance to both synthetic insecticides and Bt crops, which risks undermining the benefits delivered by these important crop protection tools. Previous modelling and empirical studies have demonstrated that releases of insecticide- or Bt-susceptible insects genetically modified to express conditional female mortality can both dilute insecticide resistance and suppress pest populations. RESULTS: Here, we describe the first germline transformation of the fall armyworm and the development of a genetically engineered male-selecting self-limiting strain, OX5382G, which exhibits complete female mortality in the absence of an additive in the larval diet. Laboratory experiments showed that males of this strain are competitive against wild-type males for copulations with wild-type females, and that the OX5382G self-limiting transgene declines rapidly to extinction in closed populations following the cessation of OX5382G male releases. Population models simulating the release of OX5382G males in tandem with Bt crops and non-Bt 'refuge' crops show that OX5382G releases can suppress fall armyworm populations and delay the spread of resistance to insecticidal proteins. CONCLUSIONS: This article describes the development of self-limiting fall armyworm designed to control this pest by suppressing pest populations, and population models that demonstrate its potential as a highly effective method of managing resistance to Bt crops in pest fall armyworm populations. Our results provide early promise for a potentially valuable future addition to integrated pest management strategies for fall armyworm and other pests for which resistance to existing crop protection measures results in damage to crops and impedes sustainable agriculture.

Modelling new insecticide-treated bed nets for malaria-vector control: how to strategically manage resistance?

BACKGROUND: The program to eradicate malaria is at a critical juncture as a new wave of insecticides for mosquito control enter their final stages of development. Previous insecticides have been deployed one-at-a-time until their utility was compromised, without the strategic management of resistance. Recent investment has led to the near-synchronous development of new insecticides, and with it the current opportunity to build resistance management into mosquito-control methods to maximize the chance of eradicating malaria. METHODS: Here, building on the parameter framework of an existing mathematical model, resistance-management strategies using multiple insecticides are compared to suggest how to deploy combinations of available and new insecticides on bed nets to achieve maximum impact. RESULTS: Although results support the use of different strategies in different settings, deploying new insecticides ideally together in (or at least as a part of) a mixture is shown to be a robust strategy across most settings. CONCLUSIONS: Substantially building on previous works, alternative solutions for the resistance management of new insecticides to be used in bed nets for malaria vector control are found. The results support a mixture product concept as the most robust way to deploy new insecticides, even if they are mixed with a pyrethroid that has lower effectiveness due to pre-existing resistance. This can help deciding on deployment strategies and policies around the sustainable use of these new anti-malaria tools.

Twenty Years of Leptosphaeria maculans Population Survey in France Suggests Pyramiding Rlm3 and Rlm7 in Rapeseed Is a Risky Resistance Management Strategy.

Strategies for plant resistance gene deployment aim to preserve their durability to highly adaptable fungal pathogens. While the pyramiding of resistance genes is often proposed as an effective way to increase their durability, molecular mechanisms by which the pathogen can overcome the resistance also are important aspects to take into account. Here, we report a counterexample where pyramiding of two resistance genes of Brassica napus, Rlm3 and Rlm7, matching the Leptosphaeria maculans avirulence genes AvrLm3 and AvrLm4-7, respectively, favored the selection of double-virulent isolates. We previously demonstrated that the presence of a functional AvrLm4-7 gene in an isolate masks the Rlm3-AvrLm3 recognition. Rlm7 was massively deployed in France since 2004. L. maculans populations were surveyed on a large scale (>7,600 isolates) over a period of 20 years, and resistance gene deployment at the regional scale was determined. Mutations in isolates overcoming both resistance genes were analyzed. All data indicated that the simultaneous success of Rlm7, the deployment of varieties pyramiding Rlm3 and Rlm7, along with the decrease in areas cultivated with Rlm3 only, contributed to the success of virulent isolates toward Rlm7, and more recently to both Rlm3 and Rlm7. Experimental field assays proved that resistance gene alternation was a better strategy compared with pyramiding in this context. Our study also illustrated an unusually high sequence diversification of AvrLm3 and AvrLm4-7 under such a selection pressure, and identified a few regions of the AvrLm4-7 protein involved in both its recognition by Rlm7 and in its AvrLm3-Rlm3 masking ability. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.