Chapter 17 Insecticides, Herbicides, and Insect Control Questions and Answers
3. Describe the basic structural feature that all organophosphates possess. What characterizes each of the following insecticides? A. Type A B. Type B C. Type C
All organophosphates contain a phosphate atom. Type A are organophosphates with no sulfur; Type B are phosphorothioates with a sulfur replacing an oxygen double bonded to phosphorous; Type C have two sulfurs attached to phosphorous.
4. Are carbamates persistent?
No they are not. Neither are organophosphates.
2. How do alternative methods of insect control differ from those used by insect exterminators?
Rather than directly killing the insect with poison or insecticides as an exterminator might, alternative methods exist which aim to which simply interfere with the insect's ability to destroy the crop or to mate and create the next generation of pests. These methods can range from directly sterilizing the insect, to preventing it from reaching maturity, to luring it away from crops through various chemicals and pheromones.
5. What is the mechanism of action of organophosphates and carbamate?
They both are acetylcholinesterase inhibitors. Organophosphates bind irreversibly; carbamates bind reversibly.
1. Describe in detail what is meant by the "pesticide treadmill."
When pesticides are applied to a population of insects, a few of them will have an evolutionary resistance to the pesticide. While most of their kin have been killed off, these resistant pests can now freely feed and reproduce with each other, increasing the number of pests with the resistant gene. The lower competition from other insects leads to a rapid resurgence of the pest, although this time they are all more resistant to the original pesticide used. The farmer suddenly finds that there are just as many pests as before and he suddenly needs a newer, deadlier pesticide to kill them. However, there will still be some which are resistant and the cycle repeats. The pests become more and more resistance while the farmer resorts to stronger and stronger pesticides.
