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

260(b) A no-choice situation. In this experiment, the eight maize genotypeswere planted in 2 replicates of 5 plants per genotype. The plants werecovered with a wire-mesh cage (150 x 150 x 150 cm) to exclude volunteerovipositing moths. Ten ovipositing moths (treated as described in thechoice situation experiment) were released in each cage. The numberof eggs laid on each leaf of each plant (counting from the base of theplant) was determined twice a week; the moths were replenished eachweek; the test period was 2-6 WAE and the ovipositional preference fordifferent leaves of the genotypes was compared.Larval ‘arrest’At 4 WAE, fi ve test plants of each genotype were each artifi ciallyinfested with 20 neonates fi rst instar larvae. The plants were coveredwith a wire-mesh cage (80 x 80 x 80 cm). The test was repeated4 times. The infested plants were dissected after 72 hours, and thepercentages of the larvae recovered from the plants were recorded.At 7 WAE, one plant of each genotype was infested with single,freshly molted third instar larvae on the outermost leaves of the whorl.The plants were covered with a wire-mesh cage (100 x 80 x 80 cm).The test was repeated in 2 replicates of 10 plants each. The infestedplants were dissected after 24 hours, and the percentages of the larvaerecovered from the plants and the site of recovery were recorded.Larval establishmentSeed of each of the eight maize genotypes were planted in two 3 mrow plots, spaced 75 cm apart with the plants spaced 25 cm apartwithin the row. Immediately after sowing, each plot was covered witha cage made of nylon net (12 meshes/cm). The cages, each being 6m long x 4.2 m wide x 3 m high, were to protect plants from naturalinfestation. Fertilizer was applied to the plots at the rate of 60 kg P ha -1at the time of planting and 60 kg N ha -1 3 WAE of the plants. Plotswere hand-weeded and irrigated as necessary.At 3 WAE, each plant of a given genotype was infested with anegg mass containing 60 eggs at the black head stage. All the plantsin a plot were infested. The egg masses were carefully placed betweenthe leaf sheath of the second leaf and the stem. Ten days afterinfestation, 10 plants in each plot were dissected and the number oflarvae recovered from each plant was recorded. Similarly, at harvest,10 plants from each plot were dissected and the number of larvae andpupae recovered from each plant were recorded.Larval feeding(a) On leaves. 20 fi rst instar larvae kept in an incubator maintained at 25°C,50-60% r.h. and 12 h photoperiod were provided with a 7-cm segmentof maize leaf whorl. After 72 h, the remaining portions of the leaf were