The ability to genetically engineer insects has opened the door to the development of new pest control techniques, notably the improvement of the sterile insect technique (SIT), in which radiation-sterilised insects are mass-released to suppress the wild population. Genetics-based methods may provide an alternative to irradiation, which can decreases the competitiveness of sterilised insects, by engineering repressible dominant lethality, a technique known as Release of Insects carrying a Dominant Lethal (RIDL®). Gene transfer and site-specific recombination technologies have here been developed in two lepidopteran pests, as the first step in the development of genetic control methods. The diamondback moth, Plutella xylostella, is a major pest of cruciferous crops and is difficult to control, mainly due to widespread resistance to insecticides, so the development of new control measures is needed. The first germline transformation of the diamondback moth has been achieved, using the piggyBac transposable element. The functionality and utility of the ΦC31 integrase, Cre and Flp recombinases in the manipulation of the diamondback moth genome has been demonstrated, and the use of recombinase-mediated cassette exchange using lox and FRT heterospecific sites has been investigated. The pink bollworm, Pectinophora gossypiella, is a significant pest of cotton. In south-western USA this moth is a target of SIT; the development of a pink bollworm female-sterile strain would remove the need for sterilisation by irradiation. Towards this end, Bombyx mori ovary-specific regulatory sequences have been tested in pink bollworm, and their potential use in the development of conditional female-sterility investigated.