Science

Genetically engineered moths wipe out wild counterparts by stopping them from breeding


A new strain of genetically engineered moth that wipes out its crop-ravaging cousins by preventing them from breeding has been released into the wild in New York state.

The diamondback moth (Plutella xylostella) causes billions of dollars of damage to crops of the brassica genus, including cabbage, broccoli and cauliflower.

But the new strain, developed with help from Oxfordshire-based biotech company Oxitec, is genetically engineered to prevent its female caterpillar offspring from surviving. 

Using the new moths, researchers from Cornell University successfully suppressed a population of diamondbacks in New York state, while preventing insecticide resistance from developing. 

The project paves the way for effective and sustainable pest control that is more environmentally friendly and at a much lower cost than insecticides, according to the researchers. 

The diamondback moth (pictured) causes billions of dollars of damage to brassica crops like cabbage and broccoli

The diamondback moth (pictured) causes billions of dollars of damage to brassica crops like cabbage and broccoli

‘When released into a field, the self-limiting male insects behaved similarly to their non-modified counterparts in terms of factors that are relevant to their future application in crop protection, such as survival and distance travelled,’ said Professor Anthony Shelton in the Department of Entomology at Cornell University’s AgriTech in New York. 

‘This study demonstrates the immense potential of this exciting technology as a highly effective pest management tool, which can protect crops in an environmentally sustainable way and is self-limiting in the environment,’ said Dr Neil Morrison, Oxitec’s agriculture lead and study co-author. 

The moths were engineered using the ‘self-limiting’ gene developed by Oxitec that disrupts the proper functioning of the insects’ cells by over-producing a protein in them.

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‘Since the self-limiting gene works by using the insect’s own biology against itself, our control method provides a solution that only affects that particular species of pest without introducing harmful toxins,’ Oxitec says on its website. 

For the study, the modified male moths were released at a research farm managed by Cornell University, in Geneva, NY, where they mated with wild pest females.

The male moths, both the engineered and wild, were then recaptured in traps, and the dispersal, persistence and field survival of each were measured.

‘For the field study, we used the “mark-release-recapture” method, which has been used for decades to study insect movement in fields,’ said Professor Shelton.

The wild females that mated with these ‘self-limiting’ males were unable to produce viable female offspring, which died soon after hatching.  

Diamondback moth (Plutella xylostella) larvae eating cabbage. The moth species is found in America, Europe, New Zealand and Asia

Diamondback moth (Plutella xylostella) larvae eating cabbage. The moth species is found in America, Europe, New Zealand and Asia

They then used mathematical models to show that that the release of engineered males could offer effective pest management of P. xylostella on a wider scale.

With sustained releases of these engineered moths, the pest population is targeted in a sustainable way compared to the use of insecticides.

What’s more, the self-limiting males do not have to have a permanent effects on moth populations.

After releases of the genetically engineered males stop, the affected insects decline and disappear from the environment within a few generations. 

While this may sound like a long time, a generation of diamondback can vary from 21 to 51 days, depending on weather and food conditions.

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The study, which was the first in the world to release self-limiting agricultural insects into an open field, has been published in Frontiers in Bioengineering and Biotechnology.

The global annual market for insecticides is projected to reach $19.27 billion by 2022, according to Statista

The global annual market for insecticides is projected to reach $19.27 billion by 2022, according to Statista 

The research builds on the sterile insect technique – releasing insects that can’t reproduce – for managing insects that was developed back in the 1950s, using radiation.  

The technique was also celebrated by Rachel Carson in her 1962 book Silent Spring, which documents the environmental effects caused by pesticides. 

‘Using genetic engineering is simply a more efficient method to get to the same end,’ said Professor Shelton.  

Arthropod pests, including moths, cause an estimated $470 billion in lost agricultural crops globally.

The main tool for controlling these pests is insecticides, the global annual market for which is projected to reach $19.27 billion by 2022, according to Statista.     

WHAT IS STERILE INSECT TECHNIQUE? 

The sterile insect technique is an environmentally-friendly insect pest control method.

It involves the the mass-rearing and sterilisation, using radiation, of a target pest.

This is followed by an area-wide release of the sterile males by air over defined areas.

They then mate with wild females resulting in no offspring and a declining pest population.

While they remain sexually competitive, the affected insects cannot produce offspring.

The sterile insect technique does not involve transgenic (genetic engineering) processes.

However, it is important to note that this new study by Oxitec and Cornell University does use transgenic techniques to control diamondback moths. 

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Source: International Atomic Energy Agency

 



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