3.1 Description of the experimental site & insecticide collection
3.1 1. Location and site
Geographically the experimental field was located at 24.75° N latitude and 90.50° E longitudes at an average height of 18 m above the mean of sea level. The experimental site belongs to the Old Brahmaputra Floodplain (AEZ-9).
3.1. 2. Soil
Non-calcareous dark-grey, floodplain soils are generally predominant in the site. The land was medium high and the soil was silty-loam and well drained
and its general fertility level was low. The soil of the experimental field was more or less neutral in nature, low in organic matter content.
3.1.3. Climate and weather
The experimental area was characterized by moderately low temperature, low humidity and scanty rainfall during the February 2014 –April 2015.
3.1.4. Insecticide collection-Botanical insecticides were collected from IPM Laboratory of Entomology Department, BAU, Mymensingh. A microbial pesticide (Beauveria bassiana) was collected from Ispahani Biotech. Company in Bolaspur, Mymensingh.Commercial formulation of Beauveria bassiana was used to conduct the experiment.
3.2 Selection of mango trees: To conduct experiments six mango trees were selected in Aqua, Mymensingh. They were marked as R1, R2, R3, R4, R5, R6. The variety of the mango was Ammapali.Trial experiment was conducted in Entomology Field Laboratory,BAU,Mymensingh.
3.3 Methodology of different experiments
3.3.1 Comparative toxicity test of a microbial pesticide (Beauveria bassiana) and some botanicals in laboratory.
This experiment was conducted in IPM Laboratory of Entomology Department, BAU, Mymensingh. The layout of experiment was designed in Completely Randomized Block Design (CRD). Four insecticides each with 3 different doses were evaluated for their effect. Both botanicals and Beauveria bassiana were used. The used botanical insecticides were neem oil, karanja oil and mahogoni oil with the dose of 1%, 2% and 3% for each insecticide. The used Beauveria bassiana which dose was 1%, 2% and 3%. For all insecticides, at first 39 petridishes (12 cm diameter) were taken. Fresh, disease free and well developed inflorescences, (approximately 10 cm in length) were collected. One inflorescence was placed in each petridish. Insecticide was sprayed on each inflorescence placed in petridishes and left for air dry before offering insect. Among the 39 petridishes, (3x3x3) = 27 petridishes were used for treatment. Then 10 hoppers (7 adult + 3 nymphs) were released at each petridish and kept for 7 days. Similarly, In case of Beauveria bassiana, 9 petridishes (12 cm diameter) were taken. Fresh, disease free and well-developed inflorescences, (approximately 10 cm in length) were collected. One inflorescence was placed in each petridish. Insecticide was sprayed on each inflorescence placed in petridishes and left for air dry before offering insect. (3x3)= 9 petridishes were used for treatment. and 3 petridishes were used for control for all insecticides. Small pieces of cotton with soaked fertilized water were placed at the base of the inflorescence to keep the inflorescence fresh. Cotton pieces were changed regularly to avoid the probability of development of fungus and some fertilized water was added to the cotton pieces regularly. The data on the number of hopper killed were collected at 1 DAT, 2 DAT, 3 DAT, 4 DAT, 5 DAT, 6 DAT and 7 DAT. Obtained data were analyzed statistically after appropriate transformation using analytical computer software MSTAT and mean values were separated using DMRT.
3.3.2 Effect of a microbial pesticide (Beauveria bassiana) and some botanicals on the infestation of mango hopper at different stages of mango
The design of the experiment was Randomized Complete Block Design (RCBD) with three replications (one plant is considered as a replication). This experiment was conducted in Aqua, Mymensingh during February 2014 – April 2015. Three plants (control plants; R4, R5 and R6) were selected which were healthy, vigor and free from insecticides application. Observations were made on 7, 30 and 45 days after flowering. To conduct the experiment at least 10 inflorescence/plant were observed.
At each observation, the data were recorded on the following parameters:
a) Number of hoppers at flowering stage at prior to first spray
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b) Number of hoppers when fruit is pea shaped at prior to second spray
c) Number of hoppers on fruiting stage at prior to days after second spray
Data obtained from observation were analyzed statistically using analytical computer Software MSTAT and mean values were separated using DMRT.
3.3.3 Effect of a microbial pesticide (Beauveria bassiana) and some botanicals on fruit setting of mango
This experiment was conducted in the Aqua, Mymensingh during February 2014 – April 2015. Standing mango trees were selected to conduct this experiment. The layout of experiment was designed in Randomized Complete Block Design (RCBD). Among the six plants, insecticides were sprayed on the three plants (marked as R1, R2, and R3) but another three plants (marked as R4, R5, and R6 )were not sprayed for control to fulfill the experiment.
Four insecticides (three botanicals and Beauveria bassiana) each with 3 different doses were evaluated for their efficacy. Both microbial and botanical insecticides were used. The used botanical insecticides were neem oil, mahogoni oil and karanja oil with the dose of 1%, 2% and 3% for each insecticide. The used microbial insecticide was Beauveria bassiana with the dose of 1%, 2% and 3%. Insecticides were sprayed two times: first spraying was done within 10 days of flowering when the flower buds were not opened and the second spraying was done after one month of the first application when the mango fruit was as pea shaped. Three inflorescences with leaves of each plant were sprayed with every doses of each insecticide. When R1 plant was only considered for spraying with Neem oil then the combinations were T1a R1 P1 ; T1b R1 P2 and T1c R1 P3 (where T1a = neem oil 1%, T1b =neem oil 2%, T1c = neem oil 3% ; R1 = plant 1, Pl, P2, P3= 1st, 2nd, 3rd inflorescence respectively). That is for each plant with four insecticide (3 doses for each) the total combination were (3x4) = 12. Some inflorescence was also kept unsprayed for control. Similar procedure was followed for another two plants. The reminder three plants were also kept for control observation. With the help of hand sprayer insecticides were sprayed to the selected inflorescence only and all the necessary precautionary measures were taken during the application of insecticides. Observation was made on the following parameters:
a) Number of flowers/inflorescence at prior to first spray with different doses of different insecticides
b) Number of fruit set at pea shaped at prior to first spray with different doses of different insecticides
c) Percentage of fruit set
The percentage of fruit set was calculated from the number of bloomed flowers and number of fertilized flowers using the following formula: Percentage of fruit set= No of fertilized flowers/No of bloomed flowers x 100
The above observations were made on 7, 30 and 45 days after flowering.
Obtained data were analyzed statistically after appropriate transformation using analytical computer software MSTAT and mean values were separated using DMRT.
3.3.4 Effect of a microbial pesticide (Beauveria bassiana) and some botanicals on fruit retention of mango
This experiment was conducted in the same place Aqua, Mymensingh during February 2014 – April 2015. The layout of experiment was Randomized Complete Block Design (RCBD) with 3 replications (1 plant was used as a unit per replication), where only two factors were considered the number of flowers and the number of fruit set. Standing mango trees were selected to conduct this experiment. The layout of experiment was designed in Randomized Complete Block Design (RCBD). Among the six plants, insecticides were sprayed on the three plants (marked as R1, R2, and R3) but another three plants (marked as R4, R5, and R6) were not sprayed for control to fulfill the experiment. Four insecticides (three botanicals and Beauveria bassiana) each with 3 different doses were evaluated for their efficacy. Both microbial and botanical insecticides were used. The used botanical insecticides were neem oil, mahogoni oil and karanja oil with the dose of 1%, 2% and 3% for each insecticide. The used microbial insecticide was Beauveria bassiana with the dose of 1%, 2% and 3%. Insecticides were sprayed two times: first spraying was done within 10 days of flowering when the flower buds were not opened and the second spraying was done after one month of the first application when the mango fruit was as pea shaped.
Three inflorescences with leaves of each plant were sprayed with every doses of each insecticide. When R1 plant was only considered for spraying with Neem oil then the combinations were T1a R1 P1 ; T1b R1 P2 and T1c R1 P3 (where T1a = neem oil 1%, T1b =neem oil 2%, T1c -= neem oil 3% ; R1 = plant 1, Pl, P2, P3= 1st, 2nd, 3rd inflorescence respectively). That is for each plant with four insecticide (3 doses for each) the total combination were (3x4) 12. Some inflorescence was also kept unsprayed for control. Similar procedure was followed for another two plants. The reminder three plants were also kept for control observation. With the help of hand sprayer insecticides were sprayed to the selected inflorescence only and all the necessary precautionary measures were taken during the application of insecticides.
Observation was made on the following parameters:
a) Number of flowers/inflorescence at prior to first spray with different doses of different insecticides
b) Number of fruit set at pea shaped at days after second spray with different doses of different insecticides
c) Percentage of fruit set
The percentage of fruit set was calculated from the number of bloomed flowers and number of fertilized flowers using the following formula: Percentage of fruit set= No of fertilized flowers/No of bloomed flowers x 100
The above observations were made on 7, 30 and 45 days after flowering. Obtained data were analyzed statistically after appropriate transformation using analytical computer software MSTAT and mean values were separated using DMRT