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Insecticide Resistance - Science topic

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So, i've added 2uL of chlorpyrifos in my culture of RT-Gill cells that were in L15 medium. The first thing that concerned me, was that it inmediatly reacted forming some tiny bubbles, like when you open a bottle of soda. Also, the color of the medium changed from colorless to redish. (See the first photo, "T" are the ones with chlorpyrifos, and "C" my control). I inmediatly thought that my cells died, but they looked fine (i think) when i saw them under a microscope. 48Hrs later, i came back to see the medium and do a protein extraction, so i took the medium but ones with chlorpyrifos left a jelly thing in the bottom (like solidified silicone), and took a bit by scraping it (see the last photo).
I honestly have no idea what caused this reaction.
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Greetings.
Check if any component of the L-15 media reacts with chlorpyrifos. Or maybe reacts wirh the serum needed for the RT-Gill growth.
Changes in the colour seems to be that there is a imbalance in pH.
Start testing some things with this ideas.
Best regards.
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Hi
I have no experience but interested to learn and apply mathematical models for insecticide resistance. It would be great if some colleague guide me from where to start. I have experience for insecticide resistance monitoring, isolines comparison, fitness cost analysis and genetics of resistance in some Lepidoptera insect pests like Spodoptera litura, Helicoverpa armigera.
Many thanks in advance
Munir
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I suggest that you find a wild population that was never sprayed with insecticides. This will be your reference population. You will be able to compare the relative resistance of other populations suspected to be resistant to the reference (=wild) population throughout time (= different months or years) and space (=different localities). See attached file.
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What could be possible reasons for insecticide resistance among insects from areas which have very little exposure of insecticides or there is no selection pressure and the areas are rich in biodiversity.
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Some insects (e.g. some aphid species) are transported passively by winds over long distances. They could have been exposed to insecticides in the region of origin, and not in the receiving region.
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Dear all,
I need some guidance or clarifications on how to calculate the effects of the combinations of insecticides when you have the adult mortality rate of individual products and of their mixture.Example: Product A: 78%; B: 50% C: 65% and their mixture 89%.
When I looked in Insecticide Resistance Monitoring, Mechanisms and Management Manual I was confused with their calculations. Best regards
Thanks in advance
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I think, to understand these interactions (insecticides A,B,C) we should test all combinations - a+b, b+c, a+c, a, b, c and control. Only this way allow to calculate synergistic or antogonistic effects. Methods of calculation may be different
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Insecticides are becoming resistant over the period, global warming knocking the door of more people being exposed to Dengue, Chikungunya and Zika virus (and other Vector-borne diseases (VBD)) across the world. Controlling mosquitoes in alternative techniques is a timely demand. Wolbachia had shown remarkable success (although in only few countries so far) for controlling dengue virus. If the technology can be used for other Aedes-borne diseases (Chikunguny, Zika) this will be a remarkable step for controling VBDs.
Any update in this area?
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According to the World Mosquito Program, the Wolbachia method is effective in reducing the transmission of Zika and chikungunya viruses as well as dengue (http://www.eliminatedengue.com/our-research). They are already testing and/or deploying in 12 countries, and their website has further progress information and research publications.
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Hi all. During a survey I obtained five individuals of Aedes aegypti in an immature stages only in one locality, so I must start a colony of this place until I get enough larvae and adults for test procedures for resistance . Could I start a colony with a low genetic variability considering that I will do resistance tests in F1, F2, ......?
I can´t find articles that compare colonies with few and several mosquitoes in the same locality. I hope you can suggest articles or experiences. Thanks
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Amruthraj Radhakrishnan It is an interesting fact, the probability that it is a resistant population.
Thanks
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Hi everyone, I am trying to find related insecticide resistance genes in a new organism. I am selecting the cds of these genes and running a tBLASTx against my de novo assembled genome. But, today I had a doubt, do I have to select those genes from the closest model specie? Or can I select the gene predicted in the closest specie? Even if this is not a model organism.
The thing is that I want to be the most sure possible when I find those genes in my genone, and, maybe, running a BLAST with predicted genes is not the best idea.
Any suggestion is welcome!
Borja Rojas
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You are on right way. Collect the candidates by blast and later verify it with other programs. Other programs which might be increasing confidence like domain/motif scan, MSA etc.
And sure you can use closely related species as not all the organism have model organism for the comparison.
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Hi everyone! I am new here.
We have de novo assembled a genome and I would like to know which genes are related to insecticide resistance. I am looking for the sequences of those genes of related species in NCBI, then I extract the cds and blast it with my transcripts. As we have also assembled the transcriptome, we have transcripts sequences too. So I do a tBLASTx search of my genes of interest vs my transcripts and find those transcripts related to insecticide resistance. This way, I can find the position of these transcripts in the genome. But, in order to sequence those genes, how can I design a PCR to amplify only one of these genes? Should I just pick the genomic sequence of one of the exons? or should I carry out a RT-PCR with the transcript sequence?
Any advice is welcome! Thanks!
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You have to annotate first your genome using De novo-assembly and transcriptome. Hence you will get a very high structural annotation quality if both sequences have a high coverage. Once you blast against your transcriptome to find the interesting candidates, you have only to go back to your annotation and pick up your gene. In case you have doubt on the sequence assembled, you can curate it manually but its not necessary to re-sequence by PRC unless if that sequence in not covered by the platform.
Hope it helps
Best
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Insect pest problems and their management is a part of modern agriculture. Pest control measures, specially the use of chemical pesticides, however, have evoked a lot of controversy and debate vis-a-vis their deleterious effects on the environment and human health in recent times. Chemical control of insects has been used for a long time, but has serious drawback. No doubt they are providing hopeful results in eradication of insect pests and diseases but they are also killing natural enemies present in soil and with crop.
To overcome these problems identification of safe molecules with better insecticidal properties having lower mammalian toxicity, safe to natural enemies etc., which fits well in the IPM concept are needed at present. Due to gradual withdrawal of synthetic insecticides, concern about the environment, increased organic production and development of insecticide resistance, alternative control methods are needed
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There are no simple answer to this excellent question, but let us start the discussion. If consumers lower their expectations concerning the % of insect damage to the crops and they are willing to pay a premium for agricultural products produced with minimal synthetic inputs, the answer can be yes.
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we have a big problem in pistachio trees, it`s a Agonoscena pistaciae Burkhardt and Lauterer (Hem.: Aphalaridae).
A. pistachiae is resistance to most of insecticide especially Neonicotinoids family.
We should increase resistance of plant.
What should we do?
Thanks.
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Dear Nasir,
The inefficiency of different insecticides against pistachio psylla is not completely relied on insect's resistance to insecticides. As well as, you should notice to plant's physiology. 
I think you can use different plant's defense inducer such as phytohormones (e.g. salicylic acid, jasmonic acid, abscisic acid, etc.). Additionally, you can reinforce the plant's immune system by micro- and macro minerals (e.g. zinc, copper, iron, manganese, magnesium, calcium). 
Keep in the mind, pest control is not dependence in one way (chemical method). I think for an unusual pest, pistachio psylla, the grower should be using different methods together. IPM is a key way for your problem. 
Kind regards, Homayoon. 
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A new study has tried to assess the genetic variants among mosquitoes that make them more susceptible to spreading deadly viral diseases such as dengue, yellow fever, Zika and chikungunya and more resistant to insecticides that are used to kill them.
LINK:
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Among the chemical components that most often act as radar are lactic acid, ammonia and carboxylic acids. Especially dangerous is lactic acid, as it is the main compound that attracts mosquitoes Aedes aegypti, a species that can be carriers of the dengue virus and yellow fever, as different studies have concluded.
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Hello, I'm planning to assess insecticide resistance of aphid and its parasitoid along with selection. There are many assays I've found in articles so far.
There are leaf dipping assay, feeding insecticide mixed with 10% sugar solution, bial assay(using residue after drying liquid in a bial).
These are the methods using insecticide directly to adult parasitoid.
And some suggested that using insecticide to the infected aphid(developing parasitoid larvae) is better.
I can't decide which method is more appropriate, but I think that contacting insecticide to adult female only make a selection slower.
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Typically the method involves developing multiple dose-response curves. This process is easier if the residue is applied uniformly because you have then eliminated variability due to toxicant distribution. This is great so long as all of the resistance in the field is due to biochemical mechanisms. This approach minimizes any behavioral sources of resistance.
Selection pressure is up to you, but a few individuals need to survive and be sufficiently healthy to reproduce. You can use the LD10, or LD50 dose as the selection tool.
Match exposure in the lab to exposure in the field. A systemic insecticide might be best tested mixed with diet, while a contact insecticide test might be more relevant as a thin film.
Be aware that "uniform" to you may not be uniform to the insect. The aphid interacts with its environment often at a sub-millimeter scale to distinguish one cell in a leaf from another.
Sometimes these assays are conducted by placing a droplet of pesticide on the insect cuticle using a microapplicator.
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I have a question about investigating insecticide ( Neonicoitnoids) resistance mechanism. We have populations of insects that are resistant and susceptible to insecticide, and we are interested to find out about the mechanism behind it. Any recommendation that how we can do it?
Looking forward to hearing your ideas.
Thanks
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This will depend on your species and the funds that you have available.
If it is a widely studied species then the resistance conferring point mutations in the Nicotinic Acetylcholine receptor may be known and you can screen for these in your samples. You can then see if frequencies differ between colonies and perhaps field-collected samples of differing resistance. If the mutations are unknown in your species you may be able to sequence particular NAChr genes and locate potential target site mutations.
You can try synergist exposure prior to bioassays to indicate the potential involvement of particular detoxification families. If metabolic resistance is indicated you can then try RNASeq to identify upregulated genes. With that information you could knockdown the gene and quantify the effect on the phenotype.
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I am doing biochemical assays for insecticide resistance in Aedes aegypti populations, micoplate assays, but I am not clear how to calculate the enzyme activity for each assay. I was wondering if I could get in touch with someone who could guide me, since is the first time I do it. Thank you very much.
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Yamili Contreras-Perera Thank you Yamili for your answer. I am doing microplate assays, as described by Brogdon, and I have done all the calibration curves. I am just not sure about doing the data analysis, the calculations. Since there is a lot of detailed information about the procedure of doing the assays, but not how to calculate after you get the absorbance. I really need someone to confirme the logic and process I am using to calculate my activites. If you think you could help me, I would really appreciate it!.
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Hello,
I have a question for designing the experiment, I am interested to design markers for insecticide resistance in an insect that its genome has not been sequenced. I am thinking to sequence the genome, do de novo assembly and then look for variants between tolerant and control insect. Is this sounds practical? How about going through transcriptomics instead?
Appreciate your comments, Mahnaz
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Hi, Mahnaz. How is your work going? In my opinion, your could figure out some different expressed genes between resistance and sensitive insect after transcriptomics sequencing. In general, the ORF is incomplete after transcriptomics sequencing, so a whole genome sequence is a very powerful database for your to obtain the full length of specific gene and your next research.
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I would like to request researchgate people to comment on the following abstract. Does this report any findings, or convey a message? What are the weakness of this abstract?
Improved design of a synthetic Bt gene stack and testing its insecticidal efficacy in the model plant Arabidopsis
Bacillus thuringiensis (Bt) insecticidal toxin protein encoded by Cry gene is a widely used technology to control insect pest in the crop field. However, development of insect resistant to Cry genes has appeared as a major threat to the durability of this approach, and thus urgent action is required to overcome this problem. Out of many available approaches, stacking of multiple Cry genes in the same plant is thought as the best strategy to delay the development of insect resistant to Cry genes. Here we report the insecticidal activity of a genetically engineered Bt gene stack consisting of Cry1B/Cry1C genes in the model plant Arabidopsis. Cry1B/Cry1C genes were designed to produce a novel version which is free of IP. Components which have the freedom to operate were used to test the insecticidal activity of the modified Cry1B/Cry1C gene stack. Availability of technology that does not require licensing agreement to use, is one of the main barrier to develop GM crops by public sector organizations in the developing countries. Thus, it is expected that the modified Cry1B/Cry1C gene stack will be a valuable tool to develop GM crops for public or humanitarian use in the developing nations.
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This abstract doesn't give any finding. it gives only suggestion about new methodology about gene transfering. the abstract needs key points about new methodology (why we are prefare, what will be happen when we use more than two Cry genes etc.)
it is still interesting subject. the review will get more attention.
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I´m rearing Anopheles and Aedes mosquitoes for insecticide resistance research. I´m looking for a simple fast method of measuring mosquito quality. I don´t think it´s the same exposing a small underfed mosquito than a big healthy one to the dose of insecticide. I´ve been looking around but wing morphometry is too tedious as I would have to analyse about 300-500 mosquitoes a month... I appreciate any ideas.
Martín Viteri
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For Anopheles, Aedes and culex we isolate individual female from the colony cage which is fed overnight on Swiss white mice , get her eggs, count them . if the number lies within normal range of wild caught females then our maintenance is good.
To start with you rear ca 100 wild caught females to build your range of normal distribution
Good luck
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Leaf reddening is the cause of stress (biotic, abiotic) indication  in sensitive short duration Bt hybrids. Irrigation, Deep vertisols, Stay green Bt hybrid/Bio-stimulants, Long duration hybrids, sucking pest suceeptablitywith insecticides / resistant hybrids and the last WSF against deficit nutrition of P,K, Mg are the causes and found remedies. Stay green colour offered by genotypes, GA3, 6 BA and Strobins and Monocrotophos conjoint additives also.
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Leaf reddening in Bt hybrid cottonRR Ambati
Agric Res. Tech. 3, 1-3
Leaf reddening in short duration rainfed Bt hybrid cotton-A reviewRR Ambati
Cotton Research and Development 31 (2), 256-261
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Glass is inert, can be cleaned with solvents and heat, so it can be reused. But plastic petri-dishes, vials, centrifuge tubes are omnipresent in laboratories, are disposable and can easily be modified. Of course one cannot use an aceton solution on polystyrene dishes or vials, but what are the disadvantages of coating plastic surfaces with insecticides for single use? 
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It is more likely that the pesticide will get bound in the plastic. Most likely adsorbed, but possibly chemically bound or diffused into the plastic. This may be good or bad.
Good: the dose that you apply is likely the dose experienced by the insect.
Bad: the dose that you apply in the field can be adsorbed, absorbed, or bound to the leaf surface. What you would like is a petri dish that mimics the physical/chemical properties of a real plant. Then you have a more realistic dose transfer model as the pesticide gets from the plant to the target insect.
Ugly: pesticides are seldom applied as a pesticide+diluent. Typically there are a range of adjuvants that are included in the formulation. These adjuvants will affect the physical and chemical interactions between the pesticide and the petri dish as well as the transfer of pesticide from the petri dish to the insect.
To make life simple, use glass because you don't know what you are getting with plastic.
You might argue that a plastic dish assay is more relevant because your application is to baseboards and floors for pest management in homes. This seems reasonable, so long as you are using the same plastics. The effect on HDPE will likely be different than the effect on polystyrene (or any other class of plastic).
If you can, match the application method to the expected application method in the field. The distribution of deposits on a surface (any surface) matters. What looks like a uniform coating to a person might have large gaps to an ant.
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I aim to detect the molecular level mechanisms in imparting insecticide resistance in S.litura. Biochemical analysis proved the role of esterase mediated resistance. Which primers/ technique for detecting nucleotide polymorphism (RAPD/ SSR) do you recommend?
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if gene is already reported then u can use gene specific primer otherwise u have to go for Differential expression study then  to detect genes responsible for resistance
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Reversal of Insecticide Resistance 
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Dose of insecticide, body coverage pigments on insect cuticle, thickness of cuticle, the rate of ability to move  are some of the characters influencing insecticide resistance 
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Is there any defined criterion for discriminating resistance as Low Moderate or High in P. xyllostella (Based on LC 50 or resistance folds over sus)?
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I have publication with similar subjects. Please see them in my profile. Thanks
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Which bioassay method is the most suitable for second instar larvae? 
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To some extent it all depends on your goal and target audience.
  For example: My goal is to monitor insecticide resistance. The target audience will most be other research scientists. Thus I will use methods like leaf dip assays to keep the variability due to application method to a minimum. This will greatly improve my ability to detect differences.
  For example: My goal is to see if Thripsaway brand is better than Bug-B-Gone in controlling thrips. In this case I want to suggest to growers that one of these products is better than the other. A leaf dip assay in this case is inappropriate because the grower will never dip his crop. The crop will be sprayed, or the product applied as a soil drench, or some such method. So here I need to make sure that the way that I apply the insecticide is relevant to how the grower will apply the insecticide.
If you have never done this type of assay before, I suggest that you plan on at least one trial run. Given that formulation and formulation adjuvants will influence product efficacy, it is very difficult to sit at a desk and choose the dosages that will make the best dose-response experiment. If this is a field trial, then use the lowest recommended label rate. You want some of the products to fail. If all treatments have 100% mortality then there are no treatment differences to discuss.
If the goal is to use insecticide treatments to manage a disease vectored by thrips, then you need more detailed methods. The problem is field applications are never 100% effective, and they are not permanent. However, with a good choice of insecticide and good planning (suitable application method, and area wide coordination) the tactic can be effective. A key piece in this effort will be to understand how the thrips feed, and how the insecticide affects thrips feeding. Issues like repellency and how feeding patterns change as the applied lethal dose degrades over time in the field to produce sublethal doses.
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I need any articles regarding insecticide resistance in termite especially pyrethroid?
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Thank you Aarti, it is very useful
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My aim is to look for expression level of insecticide resistance gene. I am working with field collected mosquitoes. How long does the RNA remains stable after the mosquito dies
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Hi,
I am not sure how long RNA remains stable in moquitoes--that usually depends on the conditions. However, I could offer some advise with regard how to prevent RNA degradation by RNases, the enzymes that chop up RNA. In order to prevent RNA degradation by RNases, I would recommend the following:
1.) Use RNAlater or Trizol to store your tissue sample (or the entire mosquito) as soon as the animal is dead. (If you use a Trizol extraction protocol, I would recommend Trizol to store the tisuue; if you use another protocol, such as Qiagen RNeasy, then I would recommend RNAlater.) Then store the tissuet at - 80 degrees until you start the extraction.
2.) Altenratively, flash freeze the tissue/animal as soon as it is dead, and then store at - 80 degrees until you start the RNA extraction protocol.
During the extraction, there are many other precautions to prevent RNA degradation, including using DEPC treated water, cleaning and spraying all surfaces with RNAseZap or other reagents, performing all the extractions under the hood, working quicky, etc. I'd be glad to give you more info in that, if you are interested.
I hope this helps.
Cheers, Oliver
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- by direct contact or by olfaction
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@Timothy,
Yes, the objective of the test;  Benmeddour Tarek only can reveal. 
Secondly I fully agree with you about No compromise on safety & residual activity & would like to add our environment too. 
The other commonly and sequentially followed worldwide criteria are  - 1. Exclusion 2. Deny Food 3. Deny Shelter and 4. last is Killing. However these are impertinent to the question asked
As far as different pesticide products, no universal product  formulation is available that could be used in all types of circumstances for different items / commodities. Therefore various pesticides formulations, each with some limitations are available in different forms like RTU, liquid, powder, gaseous state.  Selection of pesticide would depend upon the situation and the commodity, since no single pesticide is yet to be formulated that could be used in all types of situations for all items.
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I have made an insecticide efficiency experiment in the field with white grubs. I have negative values after calculation with Henderson Tilton formula, because population in the control unit was less than treatment. I want to make One Way Anova. But data set does not have normal distribution and I want to transform my data. What kind of transformation should I apply? As I know we use arcsine transformation for percentage data. However as I said before I have negative values and I don't know how to make arcsine transformation to the negative values.
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I think that it is not a problem of data transformation, but of data interpretation.
You can simply transform negative values in positive ones and do arcsine or log transformation. The problem you have it is probably to explain why you found more population after the treatment.
Good luck with your research!
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I am doing some experiment with mosquito larvae and pupa for insecticide resistance. In my work I have to do sds page analysis of these mosquito immatures using whole body lysate. Can anybody suggest me the efficient method of sample preparation (grinding and cell lysis) with complete protocol?
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Dr Willy Jablonka  is right.  However, I would suggest that at initial stage, make a whole homogenate of a large # of larvae (for mosquitoes it economical). Find total protein and load 200 µl on gel, it will tale a lot
Good luck
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We want to study the mechanisme of dubas bug OMMATISSUS LYBICUS DE BERG. resistance by using biochemical assay
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Hi,
Initially you must perform bioassay of your chemical on the doubted resistant species. Then, measure enzymes involved in resistance like P450, esterases, GSTs.
Finally prove chemically the resistance with synergists. Even if the target of your chemical is AChE you can check its inhibition by your chemical in vitro.
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Most of the populations showed polygenic (more than one gene) resistance in laboratory selected strains of insect pests..
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Do you suggest refuge techniques where areas are set aside for the pest to reproduce free of pesticide, and wherein the pests become more susceptible and then dilute the resistance genes in the whole population?
Or did you intend refuge techniques where natural areas are set aside to harbor natural enemies? This will rely on a fairly high economic injury level and a chemical control strategy that is designed to minimize impacts on natural enemies.
Or both?
All of these are great ideas, but often take considerable research to implement with a reasonable chance of success. Unfortunately we don't know if this is diamond back moth in cabbage or a new species of mite on Lychee.
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Which came first: resistance or insecticides?
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I would think that resistance genes have existed before the introduction of insecticides, at low frequency in any population  as part  of genetic diversity.  The introduction  of  insecticides would have changed natural equilibrium by increasing the frequency of resistant individuals in a population.
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Is there any correlation present in the economic threshold level and insecticide resistance in insects. As fluctuations in ETL cause variations in insecticides resistance levels must then change in insects?
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Dear Masood,
Dear All,
It depends on how was measured the EIL (economic injury level = number of pests per a plant or leaf, etc.) on pests. If EIL was measured on sensitive pests, the calculated control efficiency will be lesser on a resistant population depending on the degree of resistance.
Cost : Benefit x observed number of pests = EIL
However when calculating the cost : benefit proportion, one uses the pre-calculated efficiency % of a control intervention which will be lower in case of a resistant population. As a consequence of this relationship, the EIL value will be higher. The trouble is that this is difficult to recognise if the grower does not know the degree of pest resistance, and he will follow a falsely calculated EIL value.
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How can we determine the insecticide resistance gene frequency in stored product pest populations? Especially on Sitophilus species. Can we use Hardy-Weinberg equilibrium?
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Allele Frequencies Consider an individual locus and a population of diploid individuals where two different alleles, A and a, can be found at that locus. If your population consists of 100 individuals, then that group possesses 200 alleles for this locus (100 individuals x 2 alleles at that locus per individual). The number of A alleles present in that population expressed as a fraction of all the alleles (A or a) at that locus represents the frequency of the A allele in the population.  1. To calculate allele frequencies for populations of diploid organisms, first multiply the number of individuals in the population by 2 to obtain the total number of alleles at that locus. 
2. Select one of the alleles for your first set of calculations. Let’s first choose the A allele from the example provided above.  
a. Individuals homozygous for the A allele will each possess 2 A alleles. Multiply the number of AA homozygotes by 2 to calculate the number of A alleles. 
b. Heterozygotes will each possess only one A allele.  
c. The total number of A alleles in the population = [(the number of Aa heterozygotes) + (2 x the number of AA homozygotes)] 
3. The frequency of the A allele = [(total number of A alleles in the population) / (total number of alleles in population for that locus)] 
4. The frequency of the a allele = (1 - frequency of the A allele) 
Genotype Frequencies  Consider the same population, locus, and alleles described above. Genotype frequencies represent the abundance of each genotype within a population as a fraction of the population size. In other words, the frequency of the AA genotype represents the fraction of the population homozygous for the A allele. 
 1. To calculate genotype frequencies for populations of diploid organisms, first determine the number of individuals with each genotype present in the population. In the example used above, you would count the number of individuals with the following genotypes: AA, Aa, and aa. 
2. To determine the frequency of each genotype, divide the number of individuals with that genotype by the total number of individuals in the population.
 a. Frequency of AA genotype = # AA individuals / population size. 
b. Frequency of Aa genotype = # Aa individuals / population size.  
c. Frequency of aa genotype = # aa individuals / population size
 IMPORTANT NOTE: Unless you know that a population meets Hardy-Weinberg equilibrium assumptions, you must use the above procedure to calculate genotype frequencies. If you know that a population meets Hardy-Weinberg expectations, then you can calculate genotype frequencies using allele frequencies and the Hardy-Weinberg equations (see below).
Assertions of the Hardy-Weinberg Equilibrium Theory The Hardy-Weinberg Equilibrium
 
Theory refers to loci within populations that experience no evolutionary mechanisms (i.e., selective forces). For such populations the theory asserts that: 
1. Allele and genotype frequencies should remain constant from one generation to the next. That is, no evolution should occur at these loci.  If, at a certain gene locus, there are only two alleles each will have a frequency such that the frequency of one allele plus the other equals one.  Remember, we are discussing the frequency in a population, not in an individual.  Formally, we can state the allelic frequency in a population as follows:  
p = Frequency of allele A = freq(A) q = Frequency of allele a = freq(a) and p + q = 1  
2. Given a certain set of allele frequencies, genotype frequencies should conform to those calculated using basic probability. In a one locus/two allele system such as the one described above, the genotype frequencies should be as follows:  a. Frequency of AA genotype = (frequency of A allele)2 b. Frequency of aa genotype = (frequency of a allele)2 c. Frequency of Aa genotype = 2 x (frequency of A allele) x (frequency of a allele)   Within a population, the frequency of the possible combinations of a pair of alleles at one locus is related to the expansion of the binomial (p + q)2.  Remember that if we square one side of the equation we must square the other side, such that (p + q)2 = 12.  The expansion is  (p + q) x (p + q) = p2 + 2pq + q2 = 1, where p2 = Frequency of genotype A/A 2pq = Frequency of genotype A/a q2 = Frequency of genotype a/a 
3. If the genotype frequencies obtained from a real population do not agree with those predicted by the Hardy-Weinberg Theory, then population geneticists know that some evolutionary mechanism or mechanisms must operate on the locus of interest. Knowledge of the theory can help narrow down the possible mechanisms. Then they can use experiments to determine which potential mechanism or mechanisms operate on the locus. As such, the Hardy-Weinberg Equilibrium Theory serves as an important tool for population geneticists. 
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In order to develop biological control against cixiidae, I'm searching what kind of plant extract could be used as a repellent and/or insecticide.
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Tansy extracts, depending upon the chemotype, could also be assayed as an insecticide both for contents in pyrethrinoids but also sesquiterpenes like thujones.
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Dear colleagues, 
The literature regarding Xenopsylla cheopis (rat flea) insecticide resistance mechanisms is very scarce. So, if anyone work on this topic, or have some documents, it would be a great help.
Thank you.
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Hi Miss. Miarinjara Adélaïde, I hope this thesis can helping you and you can contact with me for anything else about Pesticides or insecticides, Thank toy so much and have a nice day
Best regards
Mohamed Ghorab  
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Ex: Mirid bugs,leafhoppers. Spidermites.Aphids. Flowerbud maggots etc
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The occurence of secondary pests in Bt crops and the underlying mechanisms were described in the following papers:
Hagenbucher, S., Wäckers, F.L., Wettestein, F.E., Olson, D.M., Ruberson, J.R., and Romeis, J. (2013). Pest tradeoffs in technology: Reduced damage by caterpillars in Bt cotton benefits aphids. Proc. Roy. Soc. B 280: 20130042. http://dx.doi.org/10.1098/rspb.2013.0042  
Faria, C.A., Wäckers, F.L., Turlings, T.C.J. (2007). Increased susceptibility of Bt maize to aphids enhances the performance of parasitoids of lepidopteran pests. PLoS ONE 7
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Basically these three enzymes are responsible for insecticide resistance.
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late Prof.dr.M.A.Q. khan university of Illinois has done a lot of work MFO,CYP etc and resistance as well, if you could find his papers you could find a lot I think.
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We want to investigate insecticide resistance levels in Phlebotomus sandflies from Syria and would like to pursue the genotypic route if possible because phenotypic work is not feasible in the war zone.
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What do you mean by genomic test?i think if you like to test the mutation that may be caused by the use of specific insecticide, this will be determined based on what type of insecticide you use and what are the target protein you like to test. I would prefer to do cDNA. So, you can detect the possible mutation that may be caused by insecticide over generations. 
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There is a growing body of litterature regarding the use of Machine Learning Techniques to build a classifier. How can one come up with such a classifier in order to build a contry-wide prediction model of insecticide resistance in malaria vectors?
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It is often easier to build a classifier than to find the data for classification. And data must contain the information about the problem, although in a hidden or a twisted way.
If you have a data about country-wise insecticide resistance, I would recommend starting from a general classifier, like Support Vector Machines (SVM) or Neural Networks. Look for a toolbox in the programming language of your choice (MATLAB, Python, etc.)
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In the context of Bt crops literature, Resistance is defined as a heritable trait conferring a pest the hability to overcome the control by the Bt crop. Several authors agree in that "insecticide resistance be defined as an individual trait, which is an inher- ited ability of an insect to tolerate doses of a toxicant that would prove lethal to the majority of individuals in the normal population of the species". Here there seems to be an equivalency of both terms, resistance and tolerance. Part of the literature suggests that resistance involves change in the proportion of susceptibles in the population, while tolerance should be reserved to the status of the population prior to exposure to the Bt crop. Crava et al (2013) state that "We used the term tolerance in the sense defined by Finney
(1971), to refer to a quantitative measure of resistance that is normally distributed among individuals within a population". Other literature use both terms interchangably. Any suggestions about finding clear definitions of these terms?
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This is a very interesting discussion and question.  There are different ways various words are used in this context by different authors and researchers.  It is therefore important to define exactly what you mean when using such terms.  I am sure there will be many answers all slightly disagreeing and agreeing with one another to this question.
To me "resistance" works at two levels.  The first is at the field level where a product or a trait no longer provides economic control of the prevailing population of pest via a heritable trait selected by the treatment.  The second is at the organism level where an indiviual has a hertiable trait which is selected for by the treatment.  So I can have a bug in my lab which is resistant to a certain toxin, if there are enough of them in the field that is resistance. 
The Insecticide Resistance Action Committee (IRAC) have tried to standarize terms.  Their deifination is useful... (http://www.irac-online.org/about/resistance/)
"Resistance may be defined as ‘a heritable change in the sensitivity of a pest population that is reflected in the repeated failure of a product to achieve the expected level of control when used according to the label recommendation for that pest species’. Cross-resistance occurs when resistance to one insecticide confers resistance to another insecticide, even where the insect has not been exposed to the latter product. Clearly, because pest insect populations are usually large in size and they breed quickly, there is always a risk that insecticide resistance may evolve, especially when insecticides are misused or over-used".
I am not so sure "Tolerance " has such a formal definitation.  So use it wisely and be clear what you mean.  An insect pest can have a baseline sensitivty (before exposure to a control agent/toxin). There will be some variation and we may conclude that some with higher LD50 are more tolerant.
Another use of "tolerant" I have employed is in IPM.  I researched predatory mite population which were initially afftected by certain fungicide sprays.  However after years of use different vineyards had populations which were affected far less - they had adapted to the spray regimes.  In this situation I used "tolerence" to describe such populations.  If they'd been a pest which was no longer controlled it would be resistance but in this case it was a beneficial organism.
Enjoyable discussion - I look forward to other views.  But in short when you use such terms be careful to describe what you mean.
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Yellow Rice Stem Borer (Scirpophaga incertulas) is a major insect pest in Indonesia, especially in Java Island. In several places, there is a population which has been resistant to insectide. We need to start a study on its behaviour and life cycle. Perhaps by rearing this insect in greenhouse condition with rice (Oryza sativa) as its natural diet, all of the informations will be provided. I would be thankful if anyone can help me by sharing any information about the method in rearing this insect.
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I found this reference for a suitable artificial diet, for the yellow rice stem borer, from 1974, Hummelen 
We have reared about 30 lepidopteran species in the 80s of last century, on artificial diets. If you are interested, I send you our recipe. You can modulate it. This might be a too long discussion for this forum. My e-mail: cmrose@gmx.de
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I am doing some experiments on the detection of biochemical mechanisms of insecticide resistance in mosquito larva. Due to some problem I am interested in preserving these larvae for 2-3 months so that later on these experiments may be continued.
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Thanks J Chillar
I have to determine the diffrent enzyme activity later from these larvae. that is why I was doubting if the enzyme activity will be lost in storing at -80 or not. 
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By the application of pyrethroids, you can enhance the resistance to neonicotinoids or vice versa. I read some information about how they can affect the same site of action, but I want more literature to be sure about this.
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Despite both insecticides had different modes of action, the degradation by means of the cytocrome P450 (e.g. oxidases) might involve the same metabolic routes. Here, I attached a link to a web page that would help you: www.irac-online.org.
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I am designing a PCR based assay to genotype an SNP within the kdr gene that is associated with insecticide resistance. I would like to validate the assay using DNA from individuals know to have the resistance allele (or at least to have the suspected allele). I'm looking for frozen/preserved individual mosquitoes and/or mosquito eggs that could be used to establish my own colony.
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Dear Eric, we have a colony of Ae. aegypti homozygous for the kdr mutations 1016 Ile + 1534 Cys and another 1534 Cys only. We could send you dry mosquitoes for your convenience. We still do not have such colonies for Ae albopictus, but DNA instead, with the kdr mutation 1534 Cys.
Bests
Ademir
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I am working to identify the mechanism of insecticides resistance in sucking insect pests by using synergists and measuring enzymes level
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Yes, they are. These names are just synonyms, different chemical nomenclature. So, the S,S,S-tributylphosphorotrithioate, 1,2,4-tributylphosphorotrithioate, tribufos...these are different names of the same substance.
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I know how to calculate the selectivity toxicity ratio under laboratory condition but I don't know under what field condition.
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Dear Dr. Abd-Ella,
Please take a look on that link (a paper published in 2010). I hope it answers your question.
Best regards,
Mohamed
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Diamondback moth develops resistance very fast.
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Flubendiamide will be very effective. Available in the market in the trade name Fame. apply at 3ml/10 litres. Green triangled, systemic and very effective at very low dosage, specific for Lepidopteran pests. But so costly (Rs. 180 for 10ml).
Alternatively, you may think of Rynaxypyr. Available in the market in the trade name Coragen and this is also Lepidopteran specific.
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Mortality below 80%: Resistance; 80-97% potential; 98% and above susceptibility.
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There should be, it may not have been passed yet but WHO has been contemplating using the 98% cutoff for susceptibility and all the rest as resistance, so the potential class is eliminated. but this is yet to be enacted
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I would like to discuss the best methods of exposure used to select resistant populations in lab conditions, such as excised leaves (up taking the solution), artificial membrane, dipping technique, or even direct exposure via vial bioassays. I know there is a lot of material covering this on the internet but I would like to hear your personal opinion and experience.
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Dear Matheus - Yes, of course the route of exposure is important and has an important bearing on how resistance traits are expressed. If you are aiming to predict likely events in the field, you should simulate as closely as possible the field exposure conditions, though this isn't always the easiest and most practical approach. My gut feeling is that systemic applications are less resistance-prone than foliar ones, but this is complicated by compounds like neonics being used commonly as both systemic and foliar treatments. Exerience at Rothamsted indicates that neonic-resistance selected in whiteflies, aphids and planthoppers (as examples) is generally expressed much more clearly in foliar than systemic bioassays, but if sufficiently potent it can also compromise the efficacy of systemic application at recommended rates. So if you merely want to explore the potential for a pest to resist a toxin, foliar treatments may be more appropriate. If you specifically want to simulate selection pressures imposed by systemic treatments, then you need to deliver the toxin by that means.