Insecticides have traditionally been used to prevent damage to crops by herbivorous insects. There is concern over the use of traditional chemical insecticides and this has led to the development of Integrated Pest Management (IPM) programmes and a search for alternative methods of control and novel insecticidal molecules. Effective implementation of EPM requires compatibility between control methods, particularly with regard to beneficial species such as parasitoids. The impact of novel control methods and insecticidal compounds on beneficial insects therefore needs to be assessed to ensure that there are no detrimental effects on the biology and behaviour of these species. When larvae of the tomato moth, Lacanobia oleracea, were fed on leaves from tomato plants expressing the snowdrop lectin Galanthus nivalis agglutinin (GNA) at a level of approximately 2% of total soluble protein, significant increases in the mean larval weight, and in the amount of food consumed were found. This resulted in an overall reduction in the mean development time to the pupal stage of approximately 7 days. The percentage survival to the adult moth was significantly increased for larvae reared on the transgenic tomato leaves compared to larvae reared on leaves from control plants. These results are in contrast to similar studies with GNA-expressing potato plants.