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Genetically Engineered Diamondback Moth Field Cage Trials
Cornell University, USA, 2015
In previous greenhouse experiments, releases of male self-limiting genetically engineered (GE) diamondback moths suppressed a target pest population and reduced the population’s resistance to an insecticide . In the summer of 2015, we assessed performance of GE male moths under more natural conditions – in large field cages – to evaluate their behavior and potential effectiveness for future diamondback moth pest management strategies.
In 2015, results of field cage experiments indicated that:
- GE and non-GE male moths showed similar longevity.
- GE male moth mating competitiveness was lower than that of non-GE males, but still in an acceptable range and higher than the performance of males in past and current mating-based pest management programs.
- Population modelling indicates that, based on performance levels of GE male moths in these field cage experiments, release of GE males during the early season will result in highly effective suppression of diamondback moth populations.
The field cage results from the experiments described here, together with population modelling, will enable design of future diamondback moth management strategies and provide evidence to support future trials.
Glasshouse cage experiments in the United Kingdom and at Cornell University, in the United States, demonstrated that the GE strain of diamondback moth, called ‘OX4319L’, can suppress a target pest population . In netted field cages, we set out to assess field performance characteristics of GE male moths to investigate their potential effectiveness in future pest management programs, and provide evidence for future biosafety assessments. In August and September 2015, a team led by Professor Anthony Shelton conducted field cage experiments at Cornell University’s New York State Agricultural Experiment Station in Geneva, New York, US.
These experiments measured mating competitiveness and longevity of GE male moths, relative to non-GE counterparts, in field cages.
These experiments were conducted under the conditions stipulated in USDA-APHIS-BRS permit 13-297-102r-a1.
How the field cage experiments were conducted
To test mating competitiveness of the engineered male moths, GE male moths and non-GE male moths, as well as female non-GE moths, were co-released into the field cages. The moths were allowed to mate freely over a period of days. Female moths were collected and, back in the laboratory, their offspring evaluated. We were able to distinguish offspring of GE and non-GE males, and counts of each group provided a measure of mating success of each male type.
Male moths collected from these field cages were used to assess relative survival of GE and non-GE male moths.
We found no significant difference between the GE and the non-GE males in either the recapture rate or their longevity in the field cages. Although mating performance was lower than the non-GE comparator insect, it was still considered in an acceptable range and exceeded the mating success of insects from previous mating-based pest management programs.
These results were incorporated into a population model designed to predict the effect of sustained releases of GE males on the population size of pest diamondback moths. The model indicated that regular releases of these GE males would lead to effective suppression of a target pest population.
In the experiments conducted in field cages, the GE moth showed a strong performance in the first trials under field conditions. The field cage longevity analysis showed that there was no significant difference between the GE and the non-GE comparator in either the recapture rate or the longevity over the time period assessed. The GE males performed well in competing against non-GE males for female mates.
Proposed Diamondback Moth Field Trials, Cornell University
Following the successful field cage trials in 2015, our objective is to study the field behavior of the male GE moths in an experimental crucifer field at Cornell University’s New York State Agricultural Experiment Station in Geneva, New York, US. The GE males showed strong performance in field cages, and studying their dispersal and survival in an open crucifer field, relative to non-GE male moths, will provide further information on the potential of the GE diamondback moth for future integrated pest management strategies on farms.
We will conduct releases of male moths of the Oxitec strain (OX4319L), used in our previous studies, and non-engineered male moths. After each release, we will monitor movement by recapturing each moth type on sticky traps distributed around the release site and outside the trial cabbage field, measuring male moth dispersal and persistence. These types of experiments, termed ‘mark-release-recapture’ trials, are a standard way for scientists to assess how an insect behaves in field conditions. The color marker carried by the GE moths will allow us to distinguish the two moth types, and based on where we recapture them and how long this happens after their release, we can estimate how far they typically travel in a field and how long they survive in the face of natural weather conditions and predators.
We anticipate releasing a few thousand moths per release in the field in these proposed early-stage trials. On a per acre basis in an infested field, this level of insects would not be considered excessive. We expect to release around 50,000 moths during the trials. Depending on the results, multiple trials will be conducted over the course of the summer.
In addition to field trials, further caged trials may also take place.
- Harvey-Samuel, T., N. Morrison, A. Walker, T. Marubbi, J. Yao, H. Collins, K. Gorman, T. G. Emyr Davies, N. Alphey, S. Warner, A. M. Shelton, L. Alphey. 2015. Pest control and resistance management through releases of insects carrying a male-selecting transgene. BMC Biology 13:49 doi:10.1186/s12915-015-0161-1
NOTE: This FAQ has been updated for 2016-2017
What is a Diamondback Moth?
The diamondback moth (DBM) (Plutella xylostella) is the world’s worst insect pest of brassica crops (cabbages, canola, broccoli, cauliflower, kale, etc.) – costing farmers $4-5 billion annually worldwide. The moths are small, about the length of two grains of rice, but females can lay upwards of 150 eggs during their lifetime and a generation can be produced in as little as two weeks. This invasive pest probably originated in Europe, but is now found throughout the world, including New York State and other states that farm brassica vegetables.
Where and when is this research taking place?
Following successful completion of laboratory and greenhouse studies in the UK and US at Cornell, contained field cage trials are planned for the summer 2015. The field trials will take place on a research farm at Cornell’s New York State Agricultural Experiment Station in Geneva, NY during the growing season of 2015. These studies will inform the next steps for further field evaluation of this moth.
What is this research?
The Diamondback Moth Project is a scientific evaluation of a way to manage local pest populations of DBM using a control method developed by Oxitec (http://www.oxitec.com/). The control method involves genetically engineering a strain of DBM to be effectively ´´sterile´´. In greenhouse studies conducted at Cornell and the UK, the release of genetically engineered (GE) male Oxitec DBM was able to control the target pest DBM populations. The Diamondback Moth Project is now taking the next step to evaluate the effectiveness of this technique for the reduction of pest DBM in controlled field trials.
The first trial will take place in contained field cages, each about 24 (length) x 12 (width) x 7 (height) feet. Cabbages and GE and non-GE DBM will be introduced into the cages. These cage studies have four objectives: a) assess mating competitiveness of male GE moths; b) assess longevity of male GE moths; c) assess the reproductive rate of pest moths; and d) test the suppressive effect of male GE moths on the pest DBM. The results of the caged studies will inform us on how the GE moths behave in outdoor conditions, and how they might be applied in future crop protection programs.
How does this pest control method work?
This approach for insect control is based on the Sterile Insect Technique (SIT), which has been used worldwide for more than 50 years to control several important insect pests. However, with traditional SIT, male insects are sterilized with radiation and then released to mate with local female pest insects of the same species. Because the males have been sterilized, there are no offspring from the mating and this reduces the pest population over time with multiple releases. A challenge of SIT is that the radiation can affect many different genes and reduce the fitness of the male insects so they are less competitive for mating with the pest population, so Oxitec scientists developed a way to produce the same sterility effect using targeted genetic control instead of radiation. How it works is that the DBM have two added genes: a ‘self-limiting’ gene that acts as the pest control to prevent offspring from surviving to adulthood, and a color marker to track and trace the insects in the environment and to distinguish Oxitec insects from the local pest ones.
Why is Cornell doing this research?
Improved methods for managing DBM are needed in New York and worldwide, and this control method, like all applications of science, requires a critical evaluation. A Cornell scientist, Professor Anthony Shelton (http://shelton.entomology.cornell.edu/), is a world expert on DBM and will be conducting the research in association with scientists from Oxitec, a spinout company from Oxford University, who developed the moth strain.
Who benefits from this research?
New York growers, as well as growers throughout the world, typically spray their crops with insecticides to reduce injury caused by DBM larvae. This has led to the insect developing resistance to most insecticides and increased levels of crop damage, as well as increased concerns about worker safety, pesticide residues on crops, and potential hazards to the environment. Using Oxitec DBM does not have these drawbacks because they control just this invasive pest. Such species-specific control and a reduced reliance on insecticides can help protect other beneficial organisms such as pollinators, predators and parasitoids.
How is this research being funded?
The field studies at Cornell are funded by USDA’s IR-4 Project (http://ir4.rutgers.edu/) and Oxitec.
Will this research negatively impact the environment or other agriculture?
No, for the following reasons:
- The proteins from the color marker and self-limiting gene are non-toxic and non-allergenic, so if a human, bird or other organism ate an Oxitec DBM the effect would be the same as eating a wild one.
- The Oxitec DBM only mates with its own species so the genes do not spread. This species-specific control is different from the use of insecticides in which other species vulnerable to insecticides, including beneficial organisms, can be affected.
- Only male DBM adults are released and they mate with local females. The released moths and their offspring die, and the female offspring die before reaching adulthood because of the self-limiting gene. This means that the insects and their genes do not persist in the environment.
- DBM only feeds on plants in the cabbage family so they will not affect other crops including corn, soybeans, apples, and other non-brassica crops.
- This research project with GE DBM will not affect certification of other types of agricultural production including organic, conventional or biotechnology.
- The moths will not survive into the next season because:
- They cannot survive the winter temperatures of upstate New York.
- The adult moths live for just a few weeks.
Are special permits required for this work?
Yes. On August 28, 2014 the Federal Register published a notice (http://www.aphis.usda.gov/brs/fedregister/BRS_20140828b.pdf) advising the public that APHIS (Animal and Plant Health Inspection Service) was making available their environmental assessment for the proposed Oxitec DBM release and would consider all comments. The APHIS comment period ended with a total of 283 comments. APHIS considered all comments and then approved a permit on November 10th, 2014 for field trial releases of the Oxitec DBM. The contained field cage study is the next step following successfully completed lab and greenhouse studies.
Where can I get additional information?
Additional information about the project can be obtained from:
- Proposal to USDA for the release, May 2014 (http://www.aphis.usda.gov/brs/aphisdocs/13_297102r_dea.pdf)
- Federal Register / Vol. 79, No. 167 / Thursday, August 28, 2014 / Notices (http://www.aphis.usda.gov/brs/fedregister/BRS_20140828b.pdf)
- Public comments on the Environmental Assessments; Availability, etc.: Field Release of Genetically Engineered Diamondback Moths (http://www.regulations.gov/#!documentDetail;D=APHIS-2014-0056-0001)
- Oxitec DBM (oxitec.com/DBM).
- More information on DBM can be seen at http://web.entomology.cornell.edu/shelton/diamondback-moth/index.html
Hawaii’s Big Island has banned or severely limited the farming of genetically engineered (GE or GM) crops, including a papaya developed by a native Hawaiian to resist a devastating virus disease. The battle over GE crops and the law enacted in Hawaii is a microcosm of the global fight determining the future of GE crops.
This 12-part series by entomologist Anthony Shelton is the first comprehensive article about a genetically engineered crop, in this case, GE papaya in Hawaii. The story describes the virus disease outbreak, the development of virus-resistant GE papaya, small-scale farmers who adopted it, the emergence of the opposition and their takeover of the democratic process, the scientist who developed the technology, and the future of GE crops.
To read the entire series, click here or follow the link below
Reposted from btbrinjal.tumblr.com (9 April 2014)
by Tony Shelton, Cornell University professor of entomology and a world expert on Bt plants
9 April 2014 – While visiting Bangladesh to conduct environmental safety assessments for Bt brinjal and help farmers develop resistant management programs to ensure the long-term durability of Bt eggplant, I visited Haidul Islam’s Bt brinjal fields on April 9. Mr. Islam was the same farmer whose crop the Financial Express on April 7 alleged was ridden with insects that Mr. Islam was spraying with insecticides.
I found the exact opposite to be true. Mr. Islam and his associate proudly showed me his field of Bt brinjal. It was free of pest damage, and they were very pleased with the crop. Normally, they would have already sprayed insecticides on the plants to control the brinjal fruit and shoot borer, but did not have to since the plants resisted their attack. They were pleased to see no borer injury — as were the rest of us who were there inspecting the crop.
Bt brinjal resists the brinjal fruit and shoot borer — by far the most destructive pest of brinjal. Females lay their eggs on young vegetative shoots, and the emerging larvae bore into the plant and kill the shoots. Larvae from eggs laid on the fruit also bore into the fruit, making it unmarketable. Neither conventional nor organic sprays provide good control because the young caterpillars burrow into the plant as soon as they hatch. To build up sufficient residues for the larvae to be exposed to the insecticide, all the eggplant tissue must be soaked with insecticide.
Because of the usual intense use of insecticide sprays to control fruit and shoot borers, some consumers refer to harvested eggplants from South Asia as “pesticide bombs.” Bt brinjal is a far safer and healthier way for farmers to control the pest and market their fruit.
Bt brinjal also allows farmers to use “integrated pest management,” or IPM, to control minor brinjal pests like aphids, thrips, leafhoppers, and whiteflies. Some of these pests can be controlled by other insects — biological control agents like ladybird beetles and lacewings. These beneficial insects are harmed by conventional and organic insecticide sprays. In using resistant plants instead of pesticides to control the borers, farmers allow beneficial insect populations to flourish.
Coupling insect-resistant plants with integrated pest management is a long-term sustainable strategy that is better for the environment, better for farmers, and better for consumer health.