The invasive stem borer, Chilo partellus, has proved to be a highly competitive colonizer in many of the areas it has invaded in eastern and southern Africa, often becoming the most injurious stem borer, and displacing native species. In coastal Kenya, there is evidence that C. partellus has partially displaced the indigenous borer, Chilo orichalcociliellus. Whether the displacement of C. orichalcociliellus will proceed toward complete extirpation in the southern coastal area of Kenya seems unlikely. Recent sampling has shown that C. orichalcociliellus continues to persist, and laboratory studies have found that C. orichalcociliellus was able to complete development in two native grasses in which C. partellus could not develop. This difference in niche breadths of the two species may account for the continued occurrence of the native species. Additionally, a parasitoid of C. partellus from Asia, Cotesia flavipes (Cameron), has been introduced and established in several countries in Africa. Evidence from coastal Kenya suggests that the introduction of C. flavipes has resulted in a marked population decrease of C. partellus, but that populations of two native borers, C. orichalcociliellus and Sesamia calamistis, have slightly increased.

In addition to the work in coastal Kenya, there is evidence of displacement of native stem borers in two other areas in Africa. In the Eastern Province of Kenya, work conducted in the 1980s found that C. partellus was present, but less abundant than Busseola fusca. However, in the same area in the late 1990s, B. fusca was rare and C. partellus was dominant. Similarly, in the Highveld region of South Africa, C. partellus has partially displaced B. fusca.

Several factors may be responsible for the competitive superiority of C. partellus over the native stem borers. Various studies have shown that C. partellus completes a generation in less time than C. orichalcociliellus. As fecundities of both species are similar, the shorter generation time is likely to lead to higher population levels, which may give the alien species a numerical advantage. A more rapid diapause termination compared to both C. orichalcociliellus and B. fusca has also been shown, which may allow C. partellus females to colonize host plants before the two native species, which would be particularly important if the native species avoid previously infested plants.