A field trial was carried out on maize at Entomology Field Laboratory under Department of Entomology, Bangladesh Agricultural University (BAU), Mymensingh during Rabi season of 2016-17. The site of the experiment belongs to the Sonatola series of the dark grey floodplain soil type under Old Brahmaputra Floodplain Agro-Ecological Zone (AEZ-9) (Alam et al., 2019a). The field was a medium high land with well-drained silty-loam texture having pH value 6.5 and moderate fertility level with 1.67% organic matter content and other nutrient components well. The condition of climate was moderately cold and high humid with frequent wind during the vegetative stage. The land was prepared well through six (06) ploughing. All fertilizers were applied during land preparation except urea and Muriate of Potash (MOP). One-fourth of urea and MOP were applied at the time of final land preparation. The nitrogen, phosphorus, potassium, sulphur and zinc fertilizers were applied in form of urea, triple superphosphate, muriate of potash, gypsum and zinc sulphate at the rate of 260, 80, 140, 50 and 4.5 kg ha-1, respectively (FRG, 2012). Maize var. BARI Hybrid Butta-09 variety was used as an experimental crop. The seed of maize (BARI Hybride Butta-09) was sown on 05 November 2016 in line. The remaining urea and MOP were applied in three equal installments at a pre-vegetative stage, full vegetative stage and early corn formation stage. Weeding, irrigation and other intercultural operation were done properly as and when necessary for better growth and development of maize. The efficacies of seven (07) insecticides viz. Carbofuran 5G@ 20g/L (T1), Chloropyriphos 50% + Cypermethrin 5%@ 1.2ml/L (T2), Emamectin benzoate 5 SG@ 1g/L (T3), Imidacloprid 20SL@ 0.3ml/L (T4), Abamactin 1.8EC@ 2.0ml/L (T5), Spinosad@ 0.4ml/L (T6) and Imidacloprid 25% + Thiram 20%@0.4g/L (T7) were selected as experimental treatments. All chemical insecticides were collected from the local market of Mymensingh Sadar. The field experiment was laid out in randomized complete block design (RCBD) with three replications with eight treatments including control. The seed of maize (BARI Hybride Butta-09) was sown on 05th November, 2016, which is the normal sowing date being practiced at the experimental fields with a plot size of 10 m2 (4m×2.5m), spacing of 60×30cm between row to row and plant to plant, respectively and the distance was 70cm between the two plots. Total number of plots was 39. Applications of mentioned seven insecticides were sprayed in the plot according to treatments, when the population of aphid was sufficient at all stages i.e. vegetative, inflorescence and cob formation stage. In field experiment, 1st sprayed in treatment wise at the time of vegetative stage, 2nd sprayed in treatment wise at the time of inflorescence and 3rd sprayed in treatment wise at the time of the cob formation stage. Spraying was started at morning time to avoid bright sunshine and drift caused by strong wind. To evaluate the efficacy of different insecticides, observation of infested plants was identified and counted from randomly selected five plants from each treated plots before and after spraying of treatments. The grain yield was received from each treatment along with control, was weighed and recorded, and data were converted into yield per hectare basis according to treatments. At the time of applied treatments, different data were collected in different parameters wise. All data of all stages were collected and compiled into average values. Data on percent infested plants before & after spray, percent reduction of infested plants over control, plant height, length of cob without husk, no. of grain cob-1, 100-grain weight, grain yield and percent increase of yield over control were recorded in treatments wisely. The percentage infestation of the plant due to damage of maize aphid and yield were calculated by using the formula.
Before statistical analysis, the data obtained were transformed to arcsine transformation. All the recorded data were compiled and tabulated for statistical analysis. The obtained data were statistically analyzed to find out the significance of differences among the treatments. The mean values of all the characters were evaluated and analysis of variance (ANOVA) following Randomized Complete Block Design was performed by using R statistics software version 3.5.3 to see the treatment effect, and the mean differences were adjudged by Duncan’s Multiple Range (DMRT) Test (Gomez and Gomez, 1984).