1. The forage grasses, Pennisetum purpureum (Napier grass) and Sorghum vulgare sudanense (Sudan grass), attract greater oviposition by stem borers than cultivated maize. 2. Non-host forage plants, Melinis minutiflora (molasses grass) and Desmodium uncinatum (silver leaf) repel female stalk borers (Chilo sp.). 3. Inter-cropping with molasses grass (Melinis minutiflora)increases parasitism, particularly by the larval parasitoid, Cotesia sesamiae, and the pupal parasitoid Dentichasmis busseolae. Meliniscontains several physiologically active compounds. Two of these inhibit oviposition (egg laying) in Chilo, even at low concentrations. 4. Molasses grass also emits a chemical, (E)-4,8-dimethyl-1, 3,7-nonatriene, which summons the borers natural enemies. 5. Napier grass also has its own defense mechanism against crop borers: when the larvae enter the stem, the plant produces a gum-like substance kills the pest. 6. Sudan grass also increases the efficiency of the natural enemies (the parasitism rate on larvae of the spotted stemborer, Chilo partellus more than tripled, from 4.8 percent to 18.9 percent when the grass was planted around maize in a field and from 0.5 percent to 6.2 percent on Busseola fusca, another important pest). 7. ICIPE has found that inter-cropping maize with the fodder legumes Desmodium uncinatum (silver leaf) and D. intortum (green leaf) reduced infestation of parasitic weed, Striga hermonthica by a factor of 40 compared to maize monocrop. Reduction in Striga infestation by inter-cropping maize with the two species of Desmodium was significantly more than inter-cropping maize with soybean, sun hemp and cowpea.
Source: http://www.fao.org/DOCREP/006/Y3951E/y3951e05.htm also primary sources are Dr Hans Herren, Director-General of ICIPE Prof John Pickett, IACR, Rothamsted