What is the reason for variation of fitness advantage and disadvantage in a resistant insect collected from different locations with same insecticide?
The same species of insect pest collected from different geographical regions reported variation of fitness cost (advantage or disadvantage) for same insecticide. The exposure of insecticide and environmental parameters may vary from location to location that may be the reason. Is there any reasons other then exposure and environmental conditions?
Conceptually, many insects can travel hundreds of miles. Some on their own, some using prevailing winds. However, in general the ability to travel long distances does not equate to realizing that capacity. Traveling long distances carries considerable risk of mortality, so most of the population is better off staying close to home. Genetic mixing between populations separated by a few kilometers will be slow unless there is some external factor enhancing such mixing (factors like trucks carrying agricultural produce that also has pests).
On a local scale one needs to understand all the factors driving the development of resistance. The number of immigrants from an external and highly resistant population. The number of immigrants from susceptible populations. The presence of untreated areas, the number of applications, the quality of those applications (coverage, dose, etc...), and the application of other pesticides with similar modes of action. Natural enemies, the quality and type of alternative hosts, and other factors like the genetic basis and stability of the resistance factors, the fitness cost of the resistance trait, and endosymbionts all combine to change the rate at which resistance develops and the stability of that resistance in the population. All told, one should not expect that the same species treated in roughly the same way in fields several kilometers apart will have the same level of resistance.
each trait may have some advantage and disadvantages, in fact it will be costs of different traits. when they are resistant they will lose some other abilities and most of time it will affect fertility or fecundity. also it must be considedred ther some plasticity and its a strong factor.
Conceptually, many insects can travel hundreds of miles. Some on their own, some using prevailing winds. However, in general the ability to travel long distances does not equate to realizing that capacity. Traveling long distances carries considerable risk of mortality, so most of the population is better off staying close to home. Genetic mixing between populations separated by a few kilometers will be slow unless there is some external factor enhancing such mixing (factors like trucks carrying agricultural produce that also has pests).
On a local scale one needs to understand all the factors driving the development of resistance. The number of immigrants from an external and highly resistant population. The number of immigrants from susceptible populations. The presence of untreated areas, the number of applications, the quality of those applications (coverage, dose, etc...), and the application of other pesticides with similar modes of action. Natural enemies, the quality and type of alternative hosts, and other factors like the genetic basis and stability of the resistance factors, the fitness cost of the resistance trait, and endosymbionts all combine to change the rate at which resistance develops and the stability of that resistance in the population. All told, one should not expect that the same species treated in roughly the same way in fields several kilometers apart will have the same level of resistance.
Hi Timothy A Ebert. Please let me know, if the population carrying with different fitness cost (advantage and disadvantage) in different geographical locations then how can we go for the management of resistance or reversal of resistance.
Management of resistance might entail use of different control methods. One notable example is use of pesticides with different mode of action from the currently used chemical. Depending with the type of pest and level of use, cultural or natural methods can be used in combination with other methods (Integrated Pest Management). For example if it is grain storage you can use; heat treatment / alternative fumigants e.g sulfuryl fluoride/ ozonation/ hermetic storage- controlled atmosphere to manage phosphine resistance (eliminating resistant strains).
So to get more relevant answers on resistance management you might need to disclose the type of pest in question.
Hi Alex Chigoverah thanks for your reply. I understood that the most common method for the management or reversal of resistance is the use of pesticide with different mode of insecticide or creation of stress through heat or others.
One of the harder aspects of resistance management through selection of insecticides with different modes of action is the coordination of growers. If neighboring fields are rotating insecticides with different modes of action, but the rotation schedule for each plot is uncoordinated then you might get a broader more permanent type of resistance.
So the best approach for developing resistance would be to take three neighboring fields and in week 1 spray field A with pesticide 1 (A1). five days later spray field B with pesticide 2 (B2), and five days later spray filed C with pesticide 3 (C3). Six weeks later spray field A with pesticide 2 (A2), five days after that apply B3, and five days later apply C1. At the next application interval apply A3, then B1, then C2. At the next interval start back with A1, and so forth. This strategy does several things.
1) It allows somewhat resistant insects to move from field to field to escape the worst of the spray.
2) It exposes insects at the edges of the non-sprayed field to sublethal doses. This border can be widened if there is considerable pesticide drift.
3) The very regular sprays are highly effective at suppressing the original population. However, insects play a number game. Spray 1 kills 99.99% of the target insects. Given an insect population of 100,000,000 this leaves 10,000 individuals in the field. The only way these individuals have survived is because they are slightly resistant, but they all have some resistance. Every spray thereafter selects for ever more resistant individuals that then breed to create a population that is unaffected by the pesticide.
The alternative is to spray all fields on day 1 with pesticide 1. Scout fields until you reach the economic injury level (EIL), and spray all field with pesticide 2. Wait until you reach the EIL, and then spray with pesticide 3. You should consider buffer areas that will be unsprayed and provide habitat for a population of the pest that is susceptible to the pesticides being used. Such natural areas can also help pollinators. These "natural areas" need to be managed to reduce the possible effect of some weed species harboring a disease that is then vectored into the crop. These natural areas may also harbor natural enemies that could become relevant depending on crop and specific cultural practices.
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