AR BN FR DE HI HU ID MS NE PT SI ES TE VI
Skip to main content

Sterile insect technique: Controlling pests with precision

Written by: Fleur Fenijn Fleur Fenijn

Reviewed by: Steve Edgington Steve Edgington

Theme: Integrated pest management

Theme: Biocontrol agents

Overview

What is sterile insect technique?

Sterile insect technique (SIT) is a form of biological insect control where large numbers of the target insect are reared and sterilized through irradiation (gamma rays or x-rays). These insects are then released into the wild. When the sterilized males mate with wild fertile females, no viable offspring are produced, reducing the population of next generation of the insect. When used in an agricultural context, this can lead to decline of a target pest population, which prevents crops from future infestation. Using this technique can reduce the amount of chemical insecticides that would otherwise need to be used against the target pest to reach similar outcomes.

Diagram of the five steps involved in applying sterile insect technique against a pest problem
Figure 1. The steps involved in sterile insect technique. Credit: Fleur Fenijn, CABI

Sterile insect technique success stories

Sterile insect technique has been successfully implemented for various pest problems around the world. It has suppressed pests threatening fruit, vegetables, livestock, fibre crops, and those acting as vectors for human disease. It began in the 1950s to combat screwworm in Venezuela and the US, and has since been used against pests like the melon fly in Okinawa, Japan, and the tsetse fly in Africa. In 2023, sterile mosquitoes were released in Tahiti to manage Dengue fever. SIT has also been successfully used to control the codling moth in apple and pear orchards in Canada’s Okanagan Valley and onion maggot in Quebec, reducing the use of the chemical chlorpyrifos by 90%1

Photos of pests successfully managed by sterile insect technique. Figure includes melon fly with corresponding damage to watermelon, and coddling moth with corresponding damage to apple.
Figure 2. Pests managed by sterile insect technique. Top: Melon fly, Bactrocera cucurbitae (Scott Bauer on Bugwood) and damage from its larvae exit hole on immature watermelon (Priyesh on Plantix). Bottom: Coddling moth (Simon Winkley & Ken Walker on Wiki, CC BY 3.0 AU) and damage from larval exit hole on apple crop (E. Beers, Washington State University).

Why do we need alternatives to Chlorpyrifos?

Introduced in 1965, the chemical chlorpyrifos has been the active ingredient in some of the best-selling pesticides worldwide due to its broad spectrum of targets. Chlorpyrifos acts by targeting the insect’s ability to transmit nerve impulses. It seems to cause neurological harm in humans too, with studies showing links between prenatal exposure to chlorpyrifos and neurodevelopment disorders during childhood2. In addition to human health concerns, chlorpyrifos is a major pollutant in waterways. A water sampling campaign launched by the Quebec ministry of the Environment between 2005 and 2007 revealed that chlorpyrifos had been detected in all samples in the Gibeault-Delisle stream, far exceeding safety limits3. In 2018, Québec’s Ministère de l’Environnement included chlorpyrifos on its list of the top five high-risk pesticides. Most farmers abandoned this pesticide as this information surfaced, and its use was completely banned in Canada in 2022.  

A container of Lorsban, the pesticide based off the neurotoxic chemical chlorpyrifos.
Figure 3. Lorsban, the chemical pesticide based on chlorpyrifos previously used against onion maggot fly and other insects in the US. Photo by Pacific Northwest Agricultural Safety and Health Center, CC BY-NC-SA 4.0. 

Case study: Sterile insect technique for onion maggot fly

Onion maggot fly (Delia antiqua) is a significant pest for Allium crops (onions, shallots, garlic, and leeks). Adult flies lay their eggs in soil near the host plants, and when larvae emerge, they bore into nearby Allium roots, killing the plant at a young stage. Onion maggot can be difficult to control due to its underground nature, preventing easy contact with sprayable insecticide. Onion maggot resistance to chlorpyrifos has also been reported in regions where large areas of onions are grown. SIT has shown great promise in protecting against this pest4.

A collage of photos including a close up of onion maggot fly, larval damage on a leek, and larval damage on yellow onion.
Figure 4. Onion maggot fly (left, credit Bladimir Bryukhov), larvae damage in leek (top right, credit Rasbak), larvae damage on yellow onion (bottom right, credit Rasbak).  

SIT has been successfully applied in the Netherlands since 1981 by the company De Groene Vlig (The Green Fly) to control onion maggot fly. The technique was imported from the Netherlands to Quebec in 2004 by Phytodata Research Company, who adopted a pink coloration step in place of the signature green coloration by De Groene Vlig. Phytodata started large-scale releases in 2011 and has since established a streamlined method for producing sterile insects and releasing them on farms.

Pupae are first reared to high numbers in quarantine facilities. As the field release period approaches, pupae are irradiated to render them sterile. The emerged sterile flies are then covered with a harmless pink powder prior to release, hence the product name, “La Mouche Rose” or “The Pink Fly”. Flies are then released at a pre-determined rate (number sterile flies/hectare) in intervals throughout the season, and monitored using sticky traps. Phytodata Research Company Inc. is the only commercial producer of sterile onion flies in North America, and currently sells directly to growers in Quebec and Ontario. SIT performs best when paired with crop rotations that are a few kilometers apart, and when there is widespread adoption of the SIT technique among farmers in dense onion growing areas5.  

A person in a green onion field using a hand lens to inspect a green onion for pests.
Figure 5. Researcher looking for onion maggot fly in green onions. Photo credit: Prisme Consortium 

The benefit of pink flies is that the more we use them, the less we need them, making it an economically viable option for growers. From 2018 to 2021, a study by Phytodata and the Ontario Ministry of Agriculture Food and Rural Affairs (OMAFRA) found a 50% reduction in second generation fertile flies in treated areas compared to controls1. In an interview by Coopérateur magazine in 2021, Anne-Marie Fortier, now Scientific Director at Phytodata, said, “The average phase-in rate (number of sterile flies/ha) decreased by nearly 90% in the first five years of use. In 2011, it was around 160,000 flies/ha for onions, while today, it is around 20,000.” Today, the cost of 20,000 sterile flies per hectare in Montérégie, the onion producing region in Quebec, is around $300. According to growers, that amount is comparable to the cost of purchasing pesticides. Paired with the MAPAQ subsidy in Quebec that covers 70-85% of the costs to those implementing SIT on their farms, the incentives for farmers are manifold.

SIT has not only brought growers immense benefits, but also made strides in environmental rehabilitation. Following implementation of the pink fly project, the Quebec ministry assessed the Gibeault-Delisle stream again in 2013 and 2014, and found average chlorpyrifos concentrations to be down by 93%6

Pink sterile flies being released in an onion field, and close-up of sterile flies covered with pink pigment.
Figure 6. Left: Sterile flies being released in an onion field in Quebec. Photo by PRISME Consortium. Right: Close up shot of sterile flies applied with pink pigment. Photo by Anne-Marie Fortier. 

Steps to implementing sterile insect technique on your farm

  1. Assessment: An agronomist visits your farm to identify the pest species. 
  1. Planning: The number of sterile insects per hectare and frequency of release is determined. 
  1. Execution: Weekly releases of sterile flies are made following natural population trends. 
  1. Monitoring: Traps are used to monitor both sterile and wild fly populations and adjustments made as necessary. 

Costs

SIT is available in Quebec and Ontario for the following Allium crops: garlic, onion, green onion and leek. Pink flies and accompanying agronomy services are offered by the Prisme Consortium, a company comprised of PRISME, Phytodata, and DataSol. Each pink fly is sold for between 1.6 and 1.75 cents depending on their stage (pupae or adult) at the time of dispatch. The overall cost of SIT ranges from $160-$1200/ha, competitive with former chemical control using chlorpyrifos ($550-$1155/ha).  

The number of flies needed can decrease while maintaining the same effectiveness as chlorpyrifos. In Quebec, a MAPAQ subsidy (valid until 2026) provides financial support to growers using SIT for 70%-85% of expenses up to $40,000 per farm. SIT is currently used on almost 40% of onion growing areas in Quebec. 

Benefits and challenges of sterile insect technique

Benefits:

  • No negative impact on soils and waterways

Challenges:

  • Requires more careful planning and coordination   
  • Mass rearing conditions can be complex for certain species  
  • Effectiveness can be reduced if neighboring farms do not participate  
  • Optimal results when crop rotations are a couple kilometres apart, which may not be ideal

Conclusion

Sterile insect technique (SIT) presents an effective, sustainable alternative to chemical insecticides for pest control. Its proven success in various global applications and significant impact in Quebec and Ontario against the onion maggot underscores its potential for broader agricultural use. Despite the need for careful planning, SIT’s long-term economic and ecological benefits make it a valuable tool in integrated pest management. 

Sources

  1. AAFC. (2022, May 27). Government of Canada. Sterile Insect Technology: A different way to manage onion maggot. Access here.  
  1. Burke, R. D. et al. (2017, August). Developmental neurotoxicity of the organophosphorus insecticide chlorpyrifos: From clinical findings to preclinical models and potential mechanisms. Journal of neurochemistry. Access here. 
  1. GIROUX, Isabelle et J. FORTIN, 2010. Pesticides dans l’eau de surface d’une zone maraîchère – Ruisseau Gibeault-Delisle dans les « terres noires » du bassin versant de la rivière Châteauguay de 2005 à 2007, ministère du Développement durable, de l’Environnement et des Parcs, Direction du suivi de l’état de l’environnement et Université Laval, Département des sols et de génie agroalimentaire, 978-2-550- 59088-0 (PDF), 28 pages. Access here. 
  1. Anne-Marie Fortier (2018). Final Report: Utilisation et maintien de l’emploi de mouches stériles en remplacement du chlorpyrifos, chez les producteurs d’oignons de la montérégie. [PDF file]. Access here. 
  1. Cranmer, T., & Cranmer, T. (2024, April 12). How sterile flies replaced Lorsban for two onion growers. ONvegetables. Access here. 
  1. GIROUX, I. 2017. Présence de pesticides dans l’eau de surface au Québec – Zones de vergers et de cultures maraîchères, 2013 à 2016. Québec, ministère du Développement durable, de l’Environnement et de la Lutte contre les changements climatiques, Direction de l’information sur les milieux aquatiques, 47 p. + 3 annexes. Access here.  

Share this page

Related articles

Looking for safe and sustainable ways of managing pests and diseases?
Is this page helpful?

We are sorry the page didn't meet your
expectations. Please let us know how
we can improve it.