Field trials were initially established at Mbita Point and at the Kenyan Agricultural Research Institute's (KARI) field site at Kitale, Trans-Nzoia District, in which 50×50 m plots of maize were compared, in terms of stem borer attack, with a similarly sized plot incorporating a surround of two rows of Napier grass. A bare patch of ground was required between the maize and the Sudan or Napier grass, so that the trap crops would not take water or soil nutrients from the main crop. Where the maize was grown as a monocrop, there was a statistically significantly higher level of stem borer attack, as measured by cutting the stems and investigating for larval mining (16.8 and 27.5% in the treatment and control plots, respectively, in Suba District, Kenya, and 10 and 20.9% in the treatment and control plots, respectively, in Trans-Nzoia district, Kenya; Khan et