Quick action in Mexico leads to eradication of pest with a taste for fresh fruit

Mexican authorities announced last week that the Mediterranean fruit fly, more commonly known as the medfly, had been successfully eradicated in the state of Colima using a nuclear technique described by the International Atomic Energy Agency (IAEA) as "birth control for pests." Mexico used the sterile insect technique (SIT) in cooperation with the IAEA and the Food and Agricultural Organization of the United Nations (FAO) to protect fruit and vegetable crops, farmers' livelihoods, and the country's economy.

The threat: Female medflies lay eggs in ripe fruits, making them unfit for sale or consumption. An outbreak detected in April 2021 in the country's largest port, Manzanillo, posed an immediate risk to crops such as carambolas, figs, guavas, mangoes, papaya, pink grapefruit, and oranges, according to the IAEA. Mexico is the world's seventh-largest producer and exporter of fresh fruits and vegetables, and quarantine restrictions would have threatened over 189 billion Mexican pesos (about $9.3 billion) annually in exports, as well as local jobs.

The solution: After receiving an emergency request for assistance in April 2021, the IAEA and FAO dispatched experts to evaluate the outbreak and help set up the eradication.

To control the outbreak, Mexico designed and implemented an emergency action plan with the assistance of FAO/IAEA experts and released more than 1.45 billion sterile male flies in Colima. The environmentally friendly SIT pest-control method uses irradiation with gamma rays to sterilize mass-reared medflies. Sterilized male medflies are released to mate with wild females but produce no offspring, causing the population to decline to the point of eradication.

Walther Enkerlin Hoeflich, an FAO/IAEA entomologist, was on the ground in Colima in the spring of 2022. He led a panel of experts who verified that the operation was implemented following international standards. "Mexico's response to the medfly outbreak in Colima was quick, professional, and efficient. Their technicians are experienced in applying the SIT thanks to the long-standing cooperation Mexico has with the IAEA and FAO in using this technique," Enkerlin Hoeflich said. "This is one more example where SIT has been successfully used to prevent, suppress, and eradicate invasive insect pests, contributing worldwide to food security and safety."

An ongoing battle: The medfly was previously eradicated in Mexico in 1982 using the SIT, but the fly does not respect national borders, and so countries must remain vigilant.

"Mexico has managed to maintain its status as a country free of the Mediterranean fly," said Francisco Ramírez y Ramírez, general director of plant health for the National Service for Agrifood Health, Safety, and Quality (SENASICA) of Mexico at an event declaring the eradication of the pest in the state of Colima. "If the Mediterranean fly had settled in the country, the consequence would have been the closure of access to national and international markets for Mexican fruits and vegetables, which ultimately would have meant economic losses for local producers," he added.

The sterile male medflies used in the Colima campaign were produced at a new facility in Metapa de Dominguez in the Mexican state of Chiapas, which has a production capacity of one billion sterile medflies per week and is the second largest such facility in the world, according to the IAEA. The new facility began operations in December 2021, and together with a partner facility in Guatemala it will help maintain a containment barrier to prevent the introduction and spread of the pest in northern Guatemala, Mexico, and the United States.