For conducting this present research work, methods and procedures were followed that are described under the following the sub-heads: 2.1 Location and Time of the Study The experiment of the research was conducted in the Entomology Field Laboratory of Entomology Department, Bangladesh Agricultural University, Mymensingh. The period of the study was from 10th January to 17th July, 2012. 2.2 Characteristics of Soil The soil of the experimental area was silty loam belonging to the Old Brahmaputra Floodplain Alluvial Tract under the Agro-Ecological Zone 9 (FAO, 2011). The selected site was a well-drained medium high land having soil pH 6.8. The nutrient status of the soil under the experimental plot at depth of 0-30 cm was analyzed at the Humboldt Soil Testing Laboratory, Department of Soil Science, Bangladesh Agricultural University, Mymensingh.
2.2.1 Weather The experimental area was characterized by tropical rainfall during the month of March to June and scattered rainfall during the rest of the year. Monthly minimum and maximum temperature, relative humidity, total rainfall and total sunshine were recorded during the period of the present study.
2.2.2 Planting Material For testing the effectiveness of botanical extracts and chemical pesticides in the experimental plots for controlling yellow stem borer (YSB), TN1 rice variety were used. After transplanting seedlings, recommended agronomic practices and fertilizer dose were applied.
2.3 Treatments The test insecticides were applied thrice, first at the tillering stage and the second at the panicle initiation stage. At each application, plants were sprayed to run-off point. Dead heart counts were taken 35 days after transplanting by counting the number of tillers showing dead heart in ten alternate stands taken diagonally in each plot. The total numbers of tillers in the same ten stands were also counted, a method used. White head counts were taken 60 days after transplanting from ten alternate stands, which taken diagonally in the plots. The total numbers of productive tillers in the same ten stands were counted. The percentage dead hearts and white heads were computed by using formula (Abbott, 1925).
2.4 Design of the Field Experiment In field, the above 5 treatments were laid out in a Randomized Complete Block Design (RCBD) with 4 replications arranged in field plots. Thus, there were 20 (5×4) unit plots altogether in the experiment. Distance between replication to replication was 0.60 m. Border between the plots was 0.60 m to facilitate different intercultural operations.
2.5 Collection of Test Insecticides
2.5.1 Dursban 20EC Common name: Chlorpyrifos. Properties: Chlorpyrifos is a broadspectrum organophosphate insecticide. It is used as an insecticide on grain, cotton, field, fruit, nut and vegetable crops, and as well as on lawns and ornamental plants. It is a systemic and contact insecticide. Chlorpyrifos acts on pests primarily as a contact poison, with some action as a stomach poison. It is available as granules, wet table powder, dust and emulsifiable concentrate. It inhibits an enzyme of the nervous system (acetylcholine esterase). This causes convulsions and paralysis.
2.5.2 Convoy 25 EC Common name: Quinalphos Properties: Quinalphos effectively controls caterpillars on fruit trees, cotton, vegetables and peanuts; scale insect on fruit trees and pest complex on rice. Quinalphos also controls aphids, bollworms, borers, leafhoppers, mites, thrips, etc. on vines, ornamentals, potatoes, soya beans, tea, coffee, cocoa, and other crops.
2.5.3 Belt 24 WG Common name: Flubendiamide. Properties: Insecticide for the control of lepidopteran larvae in tomato, pepper greenhouse. The flubendiamide belongs to a new chemical class of phthalic diamides and has a new mode of action at the biochemical level without showing cross resistance with any of the known groups of insecticides. Actsby activating receptors ryanodine (ryanodine receptor modulator) thus preventing the operation of the muscular system, paralysis and death of insects.
2.6 Plant Extracts Preparation
2.6.1 Neem (Azadirachtaindica) extract Leaves and small branches of neem (5 kg) were cut into small pieces and mixed with 10 liter water. The water was boiled for 30-50 minutes. The solution was kept to become cool for about 2 hours then filtered.
2.6.2 Tobacco (Nicotianatabacum) extract The tobacco leaf (3kg) was purchased from shop and mixed with 8 liters of water, which was boiled for 30-50 minutes, the solution was allowed to cool for about 2 hours then filtered.
2.6.3 Karanja (Pongamiaglabra) extract Leaves and small branches of Karanja (5 kg) were cut into small pieces and mixed with 10 liter water. The water was boiled for 30-50 minutes. The solution was kept to become cool for about 2 hours then filtered.
2.7 Methodology for Testing Botanicals and Chemical Insecticide
2.7.1 Insecticides effectiveness of three selected insecticides in controlling yellow stem borer Test Insecticides were sprayed to control the yellow stem borer. The effectiveness of the insecticides on the yellow stem borer population was recorded. The experiment was designed in a Randomized Complete Block Design in the standing rice plant and was replicated 3 times. Each insecticide was tested with a single dose and efficiency of the dose on yellow stem borer was compared. The spraying of insecticide doses was done in March 2012 at 35 days after transplanting for dead heart counting and 60 days after transplanting for white head counting with the help of a hand-operated sprayer it was sprayed. Care was taken to avoid spray drift on adjacent plots. The spraying was done in such a way that the spray droplet did not coalesce and drain down in the soils and whole plant was thoroughly covered by spray material. After spraying each insecticide with designed dose the sprayer was washed and cleaned properly. Before, each application, the sprayer was calibrated in order to use the right dose on the plants without wastage of insecticides by determining the quantity of water required for each plot. The control plots were not sprayed with anything.
2.7.2 Efficacy of three selected botanical extracts in controlling yellow stem borer of rice The efficacy of three botanical extracts viz., neem extract, tobacco extract and karanja extract, each having single dose along with control was tested against yellow stem borer, Scirpophaga incertulus on standing rice plant at the place of Bangladesh Agricultural University Campus, Mymensingh. The trial was conducted in a Randomized Complete Block Design and was replicated 3 times. Each botanical extract was tested at the dose of 15 ml/L and efficacy of the doses on yellow stem borer was compared. The spraying of botanical extracts was done in March 2012 at 35 days after transplanting for dead heart counting and 60 days after transplanting for white head counting with the help of a hand-operated sprayer. Care was taken to avoid spray drift on adjacent plants. The spraying was done in such a way that the spray droplet did not coalesce and drain down in the soils and whole plot was thoroughly covered by spray material. After spraying each botanical extract with designed dose the sprayer was washed and cleaned properly. Before, each application, the sprayer was calibrated in order to use the right dose on the plants without wastage of botanical extracts by determining the quantity of water required for rice plant. The control plots were not sprayed with anything. Pre-treatment data were recorded one day before application of botanical extract. For recording the data 10 hills were randomly selected from the plot for respective botanical extracts treatment and 10 hills were observed from each plot. The data on the damage symptoms either dead heart or white head per 10 hills were recorded after 7, 15, 21 days of spraying of chemical and botanical extracts. The presence of natural enemies was also observed at the time of recording the extent of damage. Yield of the treated plots were recorded and compared for their difference. The data were analyzed statistically and the mean values were separated using DMRT.