Oxitec ‘Self-Limiting Gene’ Offers Hope for Controlling Invasive Moth

The results provide another successful proof of concept for the novel approach developed by Oxitec, an Oxford University spinout company pioneering insecticide-free methods to control pest insect populations. The self-limiting gene technique has already been trialled against dengue fever-carrying mosquitos, successfully reducing their populations by over 90% in Brazil, Panama and the Cayman Islands – an unprecedented level of control by any method, and one that is leading to municipal projects following approval by the national biosafety group in Brazil for releases throughout the country.

The approach was inspired by the Sterile Insect Technique (SIT), which has been used worldwide for more than 50 years, where male insects are sterilized by radiation and released to mate with pest females. Without offspring the population crashes. Oxitec’s approach harnesses the natural reproductive instincts of the male insects, but doesn’t rely on radiation to sterilize them, which can affect many genes and the insect’s ability to mate. Instead, a self-limiting gene is carried by the insects, in this case diamondback moths. The engineered male moths are released to mate with the pest females, and because their female offspring do not survive to reproduce, the number of pest moths dwindles. The Oxitec moths also carry a color marker for monitoring.

In the new results published, scientists from the US, UK and China show that diamondback moth populations in greenhouses were well controlled within 8 weeks.

Unlike insecticides, which can affect a broad variety of insect life including bees and other beneficial insects, this approach is entirely species-specific, affecting only the targeted pest population. The self-limiting gene is also non-toxic, so the moths can be eaten by birds or other animals with no adverse effects.

“This research is opening new doors for the future of farming with pest control methods that are non-toxic and pesticide-free,” said Dr Neil Morrison, lead DBM Research Scientist at Oxitec and a co-author on the paper. “We all share an interest in safe and environmentally friendly pest control, so this is a very promising tool that could be put to good use by farmers as part of integrated pest management (IPM) strategies for healthy and sustainable agriculture.”

Co-author Tony Shelton, Professor of Entomology at Cornell University, is also an expert on IPM, and hopes that the new technology can be used as a part of more agro-ecological farming systems, including organic production. “Both conventional and organic pesticides are failing to control DBM, so it’s time for scientists and farmers to work together to find new tools,” he said.

The struggle with diamondback moth for cruciferous vegetable production costs farmers around the world up to $5 billion dollars each year. DBM is poorly controlled by current methods, especially as the moths are becoming increasingly resistant to insecticides.

“Diamondback is a serious problem for farmers in New York State and around the world – anywhere cruciferous vegetables and field crops are grown. These moths invade and attack the crops, and they are developing resistance to insecticides, so we urgently need new tools to better control them,” added Professor Shelton, who is planning follow-up studies to test the Oxitec moths under harsher, outdoor conditions in upstate New York.

These studies include field cage tests this summer, with plans for small-scale field releases in future. The upcoming trials have already been approved by the US Department of Agriculture (USDA) following extensive review by independent experts and a public consultation last year.

Oxitec’s Dr Morrison concluded: “As agricultural challenges make the coexistence of diverse pest control methods increasingly important, farmers will – more than ever – need the support of their governments, public, and the scientific community to help provide them with the tools they need to put food on our tables.”