Demand-Driven Technologies for Sustainable Maize ... - IITA

317for the researcher-managed trials. Each farmer’s fi eld was consideredas a replicate. Maize and cowpea were planted the same day on plots20 x 10 m at 0.50 m x 0.80 m density. Insecticides and fertilizer wereapplied as for the researcher-managed trials.Maize borers samplingVisits were paid every two weeks to each site from 2 WAP until the endof the cropping season. During each visit, 100 plants were randomlysampled in the four inner rows and were examined for corn borersegg masses, larvae or pupae, and for predators and parasitoids. Then,destructive sampling was done on 10 plants randomly sampled in theouter rows for open stems and ear inspection at the reproductive stage.Eggs collected were kept in plastic vials, while the larvae collected werereared individually in petri dishes on maize leaves and/or cuttings,replenished every 2 days, until the emergence of the adult moths oruntil premature mortality. Pupae were also held in separate emptyplastic cups until the emergence of adult moths.Sampling of natural enemiesDead stem borers were incubated in humid chambers and fungi thatgrew on them were isolated and identifi ed. Predators were sampledusing a modifi cation of the whole-plant netting technique (Litsinger etal. 1991). One day before sampling, a nylon net (about 2 m high) wasslipped over each of 5 randomly selected plants per plot, with its endsopened to allow free access to maize plants by both ground dwellingand fl ying arthropods. Plant netting was carried out about 2 hoursafter sunset, when predator activity on the plant canopy was highest(Hasse 1981). The next morning, plants were cut off at their bases andeach of their parts were carefully examined for predators, which werecaught and later identifi ed.Profitability of intercroppingGrain yield and its corresponding current market value were usedfor the economic analysis. The profi t derived from intercropped plotswas compared to the plots protected with insecticide. A partial budgetwas done for only costs and returns associated with the effects of thechanges in the treatment of maize. The partial budget took into accountthe revenue from maize and cowpea in treated and intercropped plots,the cost of cowpea seed, Carbofuran and its application cost, and thecowpea planting and harvesting costs.Statistical analysisA one-way analysis of variance (ANOVA) was computed. Shannon-Weiner diversity index was calculated using the following formulaH’ = -Σ (p i) (log p i), where H’ is the index of species diversity (i.e.,