Whether it is aphids or earwigs, wasps, spiders or cockroaches, most of us have a hate-list of pests we would happily have disappear from the planet. But facts get in the way of our dreams. Insect pests in particular — which damage crops and transmit deadly diseases to humans and animals — are notoriously difficult to wipe out. The non-specificity of pesticides, as well as the cost of counteracting recurrent drug resistance, has made the chemical line of attack increasingly unpopular. A more economical and ecologically friendly strategy has been to release sterile insects into the wild. Unfortunately, despite its success, this sterile insect technique (SIT) isn't perfect — the ionizing radiation that sterilizes also reduces competitiveness in the wild. By developing a transgene-based method for sterilizing insects — in this case, for Drosophila — Carsten Horn and Ernst Wimmer have now built on the virtues of SIT while increasing its effectiveness.

Of the various ways of interfering with the reproduction of pests, the authors chose to engineer males whose genetic make-up caused them to produce lethal embryos. The strategy is conceptually simple: the flies to be released would be homozygous for a dominant-lethal gene that is active only in embryos. As the lethal effector, they chose an allele of the pro-apoptotic gene hid , the expression of which was controlled by the regulatory elements of the embryo-specific sry-α gene. The whole expression system was made conditional by using the tetracycline-controlled transactivator system: hid transcription is shut down in the presence of tetracycline, and so the laboratory flies can be reared unharmed by the lethal product of hid through adding the drug to their food. In the wild, where there is no tetracycline, the hid transgene is expressed and so can do its deadly deed.

The theory behind the new method translated well into practice: lethality occurred efficiently and was restricted to embryos. When a ninefold excess of sterile males was used, the transgene did not greatly affect the animals' competitiveness for mates in laboratory experiments, and the progeny from the competitive matings was reduced by nearly 90%.

In addition, although the system was established and tested in Drosophila, all the constructs, selectable markers and genes used in this study should be transferable to most other insect species — such as moths and butterflies — for which germline transformation is possible. As the SIT technique often works more effectively if only males are released, one plan is to aid the sex sorting of the engineered strain by integrating this transgenic method with a similar one that systematically kills adult females.

Transferring the new SIT technique from the bench to the field might take some time, but with luck it will give pests a much tougher bone to chew.