Four mechanisms within the resource concentration hypothesis influenceOstrinia furnacalis(Guenée) densities. Fewer ovipositing moths were attracted to (1) low density maize (<20,000 plants/ha) and to (2) small patches (<325 m2). (3) In small patches more females oviposited in monocropped than intercropped maize, when offered a choice. Companion crops may interfere with chemical or visual cues emanating from maize. (4) The companion crop may act as a barrier to silk-dispersing first-instar larvae. Plant density and patch size act independently of intercropping, although intercrops are often planted at low maize density. However, the degree of maize borer control from the combined mechanisms is low and intercropping cannot be recommended as a sole means of control. Although important, there was no evidence that intercropping affected natural enemy abundance or that there was any significance to diurnal microclimatic differences of an intercrop. Maize borer behavior in small patches has implications for experimental design of intercropping trials.