I would like to measure the attractive and the repellent effect of certain essential oils, is there an apparatus or a well known method to perform this experiment?
Hello Ammar:
You can measure the attactive and repellent effect of certain chemicals toward insects with a two-way olfactometer in no-choice bioassays to expose the insect to the odor of certain chemicals. Olfactometer experiments are commonly used in chemical ecology research to study how arthropods locate their hosts. For instance you can test to what extend volatile organic compounds emitted at different concentrations are used by herbivores (plant antagonists themselves) to localize their food plant evaluated. Also how males are attracted to the sex pheromones in bioassays with synthetic pheromones. In the following link you can find additional information and methodologies used to measure the attactive and repellent effect of plant volátiles in insects. http://www.invasive.org/proceedings/pdfs/10_615-619.pdf
Regards,
Luis Miguel
Hello Ammar:
You can measure the attactive and repellent effect of certain chemicals toward insects with a two-way olfactometer in no-choice bioassays to expose the insect to the odor of certain chemicals. Olfactometer experiments are commonly used in chemical ecology research to study how arthropods locate their hosts. For instance you can test to what extend volatile organic compounds emitted at different concentrations are used by herbivores (plant antagonists themselves) to localize their food plant evaluated. Also how males are attracted to the sex pheromones in bioassays with synthetic pheromones. In the following link you can find additional information and methodologies used to measure the attactive and repellent effect of plant volátiles in insects. http://www.invasive.org/proceedings/pdfs/10_615-619.pdf
Regards,
Luis Miguel
Olfactometer assessment is right way. It could be four arm or Y tube.
Experimental Bio-assay with an olfactometer choice chamber is a right technique for measuring attractive and repulsive effect of any living organism towards any substance having odor or fragrance.
we have used a 4-arm olfactometer to study the semiochemical behavior of red palm weevil. It is an excellent device.
Hi, olfactometers are great and widely used in chemical ecology for measuring attraction. You can use them to measure repulsion only if you combine an attractant. So, you can measure first attraction in the absence of repellent (positive control) and then add the repellent to see whether or not attraction disappears. Olfactometers have, however, some limitations and you need to pay attention to a couple of facts.
First, olfactometers using air currents rely on the fact that response of insects to chemicals is based on a mechanism of chemically triggered anemotaxis, i.e., when the insect detects the odour, it moves upwind. If other orientation mechanism is involved (as is frequently the case), as for exemple true chemotaxis or chemokinesis, the experiences conducted in an olfactometer could render false negative results, e.g. when you are testing contact pheromones.
Second, you need to pay attention to the statistics associated to your experiments, in particular for avoiding pseudoreplication. In dual choice experiments this is not complicated, but in situations of multiple choice, as in four-arms olfactometers, to apply the right statistical analysis is not straightforward. In both cases, it is very frequent the wrong use of tests for independent samples (e.g. Chi-square) to data that are not independent.
For testing repellence, it depends on the question. If you interested in orientation, the best solution is using a locomotion compensator. If you are interested in contact repellence, you can use an arena and analyse permanence time.
Good luck and all the best,
Claudio
we have used the arena partitioned in 12-24 sectors for non-flying insects (colorado beetle adults and larvae) in choice tests and we registered periods from locating the insect to start of feeding by treated leaves. If you must check the repellent activity, you can register the length of distance from treated sample to insect during 10-15 min
Keep in mind that laboratory responses may be quite different from field responses. So after assessing lab responses you should test in the field using baited traps, choosing sites where the insect normally occurs and where background levels of other volatile chemicals are what would be experienced in nature. In order to assess repellency, of course, you'll need to have an attractant to challenge the repellency. Finally once you've got trap-based results, the final proof is to test the materials for plant (or other host) protection from the insect. Again, the results from host-protection tests are not always congruent with results from trap-based tests, probably because many other cues are in play. We have found with bark beetles, for example, that it's much easier to "protect" a trap than it is to "protect" a tree using behavioral chemicals.
You can rub the part of the host that exposed to the targeted insect with the oil and make it available to it and count the insects those landing on the host per hour during the insect feeding time, and on the same time you have control host which you don't rub with the oil, WHO Guideline will help you.
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