Pesticide Resistance Management
Dr. Siegfried
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02/12/2019
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(Approx. 6 minutes)
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- [00:00:00.000][Pesticide Resistance Management title slide]
- [00:00:09.500]Many biologists consider insects to be the most successful type of organism on the planet.
- [00:00:17.000]Insects are champions in adapting to change in their environment.
- [00:00:21.500]Biologists that study insects are entomologists.
- [00:00:25.500]These three entomologists [Sek-Yee Tan, John Wang, Chen Hong] work in the laboratory of Dr. Blair Siegfried at the University of Nebraska.
- [00:00:33.000]They know that populations of the insects they study will change when two things occur.
- [00:00:40.000]One, there is genetic variation among the members of the population.
- [00:00:45.000]And two, there is some factor in the environment that applies selection pressure.
- [00:00:51.000]One insect that has evolved or changed to remain a
- [00:00:55.000]successful corn pest is the western corn rootworm.
- [00:01:00.000]This insect has a history of evolving resistance to pesticides.
- [00:01:04.500]Blair Siegfried's team of University of Nebraska entomologists
- [00:01:09.500]is focused on knowing more about the genetic makeup of the western corn rootworm populations
- [00:01:17.000]and they are experts at working with the insect at the individual and the molecular level.
- [00:01:24.500]The adult beetles captured from natural populations are brought to their laboratory for study.
- [00:01:31.500]The beetles' reaction to a precise dose of a chemical pesticide can be determined in a bioassay.
- [00:01:40.000]The entomologists know the genetic cause of evolved resistance in corn rootworms
- [00:01:46.000]to a class of chemical pesticides.
- [00:01:49.000]These pesticides are not used by farmers today,
- [00:01:54.000]but were at one time commonly applied to the western corn rootworm
- [00:01:59.000]immature stages that feed on corn roots.
- [00:02:04.000][Dr. Blair Siegfried] So the insecticides that were commonly used for western corn rootworm control
- [00:02:09.000]back in the 1940s and throughout the 1950s
- [00:02:13.000]were a group of compounds that were very, very persistent,
- [00:02:19.000]stayed in the environment for long periods of time.
- [00:02:23.500]But in addition to those adverse environmental effects,
- [00:02:27.500]they also caused high levels of resistance to develop
- [00:02:31.500]in a lot of different insect pests,
- [00:02:34.500]of which western corn rootworms were one that had developed resistance.
- [00:02:39.500]And in fact, growers stopped using these compounds in the early 1960s
- [00:02:46.500]because of resistance even before they were banned by the EPA.
- [00:02:50.500]So we now know that
- [00:02:53.000]the resistance to these insecticides is conferred by a single mutation
- [00:03:00.500]in the target site genes, or the insecticide
- [00:03:04.580]are compounds, toxins that affect the function of the nervous system.
- [00:03:11.570]And there is a specific receptor in the nervous system that has changed very slightly
- [00:03:19.570]through a single nucleotide substitution.
- [00:03:23.570]And now we can detect the presence of that mutation using PCR techniques.
- [00:03:30.570]Initially, we need to extract the DNA from individual insects.
- [00:03:36.570]Primers have been designed so we can amplify a piece of DNA that surrounds that mutation.
- [00:03:43.570]And then we can sequence that piece of DNA to determine if the mutation exists.
- [00:03:50.570]Scientists are motivated to make new discoveries about the biology and control of insects.
- [00:03:57.570]There is a new technology available
- [00:03:59.570]that
- [00:04:00.570]works to control western corn rootworm and other corn insect pests.
- [00:04:05.570]This technology uses genetic engineering
- [00:04:08.570]and allows the plant to control insect pests by making Bt proteins.
- [00:04:14.570]The new technologies that are being developed for western corn rootworm control
- [00:04:20.570]involve these toxins from the bacteria Bacillus thuringiensis.
- [00:04:25.570]So they can take these proteins and have them expressed in a corn plant
- [00:04:29.570]and so provide season long control against rootworm pests.
- [00:04:34.570]But there's a lot of concern that this technology will be like all the other insecticides
- [00:04:39.570]that have been used against rootworms and that resistance will develop quickly
- [00:04:43.570]and so there's a lot of interest in using the technology
- [00:04:47.570]in ways that will prevent resistance from evolving.
- [00:04:51.570]We've been doing laboratory selection experiments
- [00:04:54.570]where we rear these insects in the laboratory.
- [00:04:57.570]We expose them to the Bt proteins
- [00:04:58.570]We expose them to the Bt proteins
- [00:05:01.570]throughout development of the immature stages.
- [00:05:05.570]Those insects that survive go on to reproduce
- [00:05:08.570]and produce the next generation,
- [00:05:12.570]which we can then select again.
- [00:05:14.570]And over time we can see how susceptibility changes
- [00:05:18.570]in response to that selection.
- [00:05:22.570]And so hopefully this kind of simulated selection
- [00:05:27.570]will give us some clues about what might happen
- [00:05:30.570]in the field when these insects are exposed.
- [00:05:33.570]To better understand the western corn rootworm populations
- [00:05:37.570]and their tendency to change their gene pool,
- [00:05:40.570]the University of Nebraska team has a plan
- [00:05:43.570]that will take advantage of what they learned
- [00:05:46.570]about the western corn rootworm genetic response
- [00:05:49.570]to the old chemical pesticides.
- [00:05:53.570]In the next video, we will learn how the UNL team
- [00:05:56.570]carries out these experiments
- [00:05:59.570]and how their results will help them make better predictions
- [00:06:02.570]about the insect's response to the new Bt pesticides.
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