Existing and impending constraints to the use of synthetic pesticides, along with changing legislation in favour of an integrated approach to pest management, are driving uptake of ‘alternative’ approaches to pest control. Polyculture is one such approach, often relying upon the presence of non-hostplants within the crop to reduce colonisation by pest insects. The diamondback moth, Plutella xylostella (L.), is known to oviposit on non-hostplants and the present study showed that neonates were able to move relatively large distances, enabling them to relocate from non-host natal plants to nearby hosts. Although fewer larvae were found on hostplants when they hatched on non-hosts, it is concluded that even a low level of re-location of neonates could potentially reduce the potential for polyculture to control this pest. It is proposed that non-host oviposition and neonatemovement could explain why polyculture sometimes fails in controlling pest insects.