The experiment was conducted at the experimental field of Entomology Division, BARI, Gazipur during Rabi 2007-08. BARI tomato 2 (Ratan) seeds were collected from Olericulture Division, Horticulture Research Center (HRC), BARI, Gazipur. Tomato seeds were sown in beds of 3mx1m size in 5cm apart rows for raising seedlings. One month old healthy seedlings of equal height were selected for transplanting in the experimental plots. Standard agronomic practice such as watering, gap filling, application of fertilizer, weeding, stalking were followed during the study period.
Treatments: Two microbial insecticides viz. HaNPV and Bt were used in this experiment. The treatments were as follows: T1= HaNPV (Heli-Cide 100 LE 1x109 POB/ml) spraying @ 0.4 ml/L of water at 10 days interval, T2= Bt (BACILLUS THURIGIENSIS, Halt 5% WP) spraying @ 2.0 g/L of water at 10 days interval, T3= HaNPV @ 0.4 ml/L of water and Bt @ 2.0 g/L of water alternate spraying at 10 days interval, T4 = Control
Design and layout: The experiment was laid out in randomized complete block design (RCBD) with three replications. The unit plot size was 3.6m x 3.0m with a distance of 100 cm between the plots and 150 cm between the blocks. In unit plots, row to row distance was 60 cm and plant to plant was 40 cm.
Treatment application: Microbial insecticides were first sprayed just before flower initiation stage and then 2nd, 3rd 4th and 5th sprays were done at 10 days interval with the help of Knapsac sprayer. Four liter of spray material was required to spray three plots before fruiting stage, subsequent applications required five liters each. At the time of spray the target plot was surrounded by temporary polythene walls to avoid dripping to the adjacent plots. The spray was done uniformly on entire plant to ensure complete coverage with Knapsack sprayer. Spraying was done in the afternoon to escape bright sun, strong wind and pollinating bees.
Collection of data: Procedure for data collection and calculation of percent fruit infestation by number at in-situ condition, percent fruit infestation by number and weight at harvest, yield data at each harvest.
Percent fruit infestations by number at in-situ condition: In this case the data recording were started just after first fruit set. All fruits of six plants per plot were considered for data recording. Data on fruit infestation by number were recorded at 7 days interval. Percent fruit infestation by number at in-situ was determined using the following formula:
Number of infested fruits
% Fruit infestation by number = x 100
Total number of fruits
Per cent fruit infestation by number: At harvest, the total fruits were sorted into healthy and infested ones for each treatment. On the basis of the number of total fruits (TF) and infested fruits (IF) the percent fruit infestation was calculated using the following formula:
Number of infested fruits
% Fruit infestation by number = x 100
Total number of fruits
Per cent fruit infestation by weight: Accordingly, the weight of infested (bored) and weight total fruits were recorded and the per cent fruit infestation by weight was determined using the following formula:
Weight of infested fruits
% Fruit infestation by weight = x 100
Weight of total fruits
Marginal Benefit cost ratio: The marginal benefit cost ratio was calculated on the basis of prevailing market prices of tomato, microbials and spraying cost. Marginal benefit cost ratio was calculated as follows:
Benefit on control
% Marginal BCR =
Cost of treatment