Nine million sterile males to be released in the Valencian Community to combat the tiger mosquito

Nine million sterile males to be released in the Valencian Community to combat the tiger mosquito

Image of Aedes Albopictus - Tiger Mosquito. Credit: Wikipedia - By James Gathany, CDC (PHIL) Public Domain

In an ongoing project to combat the tiger mosquito, nine million sterile males are being released in the Valencian Community.

The Ministry of Agriculture, Rural Development, Climate Emergency and Ecological Transition announced that it will increase the release of male tiger mosquitoes this year to nine million specimens.

This is part of a pilot project of biological control through the Sterile Insect Technique (TIE) that the government department has been promoting since 2017 in the Ribera Baixa region of Valencia.

In previous years, this technique has reportedly managed to reduce the population of tiger mosquitoes by up to 75 per cent. This figure is based on the monitoring that technicians conduct in the municipality where the releases are carried out.

Eight million insects were released in the Ribera Baixa in 2022. The release of sterile males was resumed at the end of February in this new season in order to anticipate the appearance of the first wild individuals, which usually occurs in springtime.

The Sterile Insect Technique (SIT) is a method of biological pest control that consists of the mass breeding of male insects of the same species that are intended to be combated. They are sterilised by irradiation and subsequently released in the area of ​​action.

These sterile males mate with wild females, which causes the eggs they produce to be inviable. As a result, no offspring are produced, resulting in reduced levels of the pest.

This is the same technique that the department has used in the fight against the Mediterranean fly (Ceratitis capitata) in citrus fruits. In the case of the tiger mosquito (Aedes albopictus), it is the female that causes the annoying bites, so the release of males has no impact on the members of the public.

Roger Llanes, the regional secretary for Agriculture, explained that as the capacity to produce sterile insects has improved, releases have also increased.

The problem generated by the expansion of the tiger mosquito led the Department of Agriculture to design a pilot project for biological control that began six years ago in the Ribera Baixa. These pests were first detected in the Valencian Community in 2005, in the town of Orihuela.

Specifically, the technicians selected the towns of Polinyà de Xúquer and Albalat de la Ribera for this purpose. Initially, they carried out the release of sterilised males.

A second release was used as the ‘control’ municipality, until, last year, the fieldwork was expanded and five million mosquitoes were released in Albalat. In this new phase, the towns of Riola and Llaurí have been selected as mirror or control areas.

Good results were achieved from the outset due to the increase in the production capacity of sterile males. This was achieved thanks to the development of technology and equipment. That led to a fourfold increase in the area in which males were being released in recent years.

In addition to expanding the study area in the Ribera Baixa, the Ministry has also introduced the project to Vilavella in Castellón, and Paterna.

These field works to curb the expansion of the tiger mosquito include the evaluation of different control strategies in various urban environments. The aim is to determine the variables that influence the success of the SIT in controlling the pests as well as the effect of different complementary fighting methods.

According to sources from the Ministry, different complementary control methods are being evaluated. These include the installation of traps, the release of sterile males in peripheral areas, the application of biological larvicides, and awareness and citizen participation.

With all the fieldwork, the aim is to define a program for the integrated fight against the tiger mosquito that allows the effective reduction of the wild populations of this pest.

Tiger mosquitoes are already present in practically all of the Valencian Community. This not only causes discomfort due to their bites but is also a vector of up to 22 diseases. Among these, Dengue, Zika, and Chikungunya stand out, as reported by

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Written by

Chris King

Originally from Wales, Chris spent years on the Costa del Sol before moving to the Algarve where he is a web reporter for The Euro Weekly News covering international and Spanish national news. Got a news story you want to share? Then get in touch at