The present invention provides a method for reducing the incidence of resistance of pests to pesticidal plants. In particular, there is provided a locus at which plant pests feed comprising at least two regions, characterised in that: a) a first region comprises plants which produce at least a first pesticidal toxin; and b) a second region comprises plants which produce at least a second pesticidal toxin; wherein a pest which can develop resistance to the first toxin does not develop resistance to the second toxin, and the first region comprises plants which produce the first toxin but not the second toxin when the plants of the second region produce the second toxin but not the first toxin. In one aspect of the invention, the plant pests are insects. The invention also provides a method for controlling insects.