Management of brinjal shoot and fruit borer , Leucinodes orbonalis ( Lepidoptera : crambidae ) using some selected insecticides in field condition , Bangladesh

Experiments were carried out in two consecutive cropping seasons to evaluate the effectiveness of seven insecticides against brinjal shoot and fruit borer (BSFB) in the experimental farm of the department of Entomology, BSMRAU, Bangladesh. Tracer-45 SC was found to be highly effective in reducing 88.22 % and 84.41 % shoot infestation over control during summer and winter, respectively followed by Proclaim-5 SG (74.12 % in summer and 64.36 % in winter). The highest number of healthy fruits per plant (22.38 in summer and 35.69 in winter, respectively) and the highest yield of eggplant per hectare (19.94 t/ha in summer and 24.79 t/ha in winter) were obtained from Tracer-45 SC treated plots. Therefore, it may be concluded that Tracer-45 SC (Spinosad) @ 0.4 ml/liter could be the most effective insecticide in controlling brinjal shoot and fruit borer and also in getting highest yield of eggplant.


INTRODUCTION
Brinjal (Solanum melongena), also known as eggplant, belongs to the family Solanaceae.Its fruit commonly known as vegetable which is the most popular in Bangladesh.It is extensively grown both in summer and winter seasons and is available throughout the year.In Bangladesh, more than 70% of the total vegetables are produced in Rabi season and less than 30% in the Kharif season (Hussain & Awrangeb 1992).Nayar et al. (1995) reported 53 species of insect pests of brinjal among which brinjal shoot and fruit borer, Leucinodes orbonalis Guenee (Lepidoptera: Pyralidae), is the major and most destructive one in Bangladesh and throughout Asia.Larvae bore into shoots during the vegetative stage and later in flowers and fruits, rendering the latter unfit for human consumption.The yield loss caused by this pest is enormous and varies from 37% to 63% in different parts of India (Dhankar, 1988), up to 67% every year in Bangladesh (Islam & Karim, 1991).Latif, 2007 reported that Nimbicidene and Flubebdiamite were comparatively safe for natural enemies and insect pest management of brinjal on the other hand, Tohnishi et al. (2005) reported that flubendiamide was highly toxic to Lepidopteran insect pests but it was very safe for different natural enemies like ladybird beetles, spiders, parasitic wasp, lacewings, predatory bug and predatory mite.
In summer, temperature, relative humidity and rainfall remains high, while in winter conditions remain reverse.Depending on the weather condition, the prevalence of BSFB differs and it causes significant infestation in both the seasons.The effectiveness or performance of the insecticides are also greatly influenced by the temperature, relative humidity and rainfall under field conditions.The aim of this study was to investigate the comparative effectiveness of seven insecticides against BSFB in both the seasons and also to find out the most effective insecticide (s) for suppressing BSFB under field condition.

MATERIALS AND METHODS
Experiments were conducted in the experimental farm of the department of Entomology, Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU), Gazipur, Bangladesh in two consecutive cropping seasons i.e. during summer (April to September 2009) and winter (November 2009 to May 2010).The experiments were laid out in a randomized complete block design (RCBD) with 3 replications.The whole field was divided into 3 blocks of equal size having space of 2 meters between blocks and 1.5 meters between plots.Each block was subdivided into 8 equal plots (Treatments) including one control plot.The unit plot size was 3m x 3m accommodating 15 pits per plot.The distance between rows were 1m and that of plants were 60 cm.The application of manures and chemical fertilizers were done following by the method described by Rashid (1993).Seeds of brinjal variety BARI brinjal-8 were collected from the Horticultural Research Center (HRC) of Bangladesh Agricultural Research Institute (BARI), Joydebpur, Gazipur.A small seed bed measuring 5 m x 1 m was prepared and seeds were sown in the nursery bed at Experimental field of the Department Entomology, BSMRAU, on 6 March 2009 for summer season and on 7 October 2009 for winter season.A total of 360 seedlings having 35 days old were planted in 24 plots @ 15 seedlings per plot with spacing of row to row 1.00 m and seedling to seedling 60 cm.Weeding in the plots were done as and when necessary.

Shoot infestation:
The total numbers of shoots and the number of infested shoots were recorded from randomly selected 5 plants per plot at weekly intervals.Percent Shoot infestation was calculated using the following formula: Fruit infestation and yield per hectare: After harvesting fruits at 7 days intervals, the healthy and infested fruits were sorted out.The weight of healthy and infested fruits of each plot for each treatment was noted separately.Fourteen harvests were made throughout the fruiting season and percent fruit infestation by number and weight was calculated using the following formulae: The cumulative plot yield of healthy, infested and total fruits of 12 harvests were transformed into healthy, infested and total yield per ha in tons.

Statistical analysis:
Data were analyzed by using MSTAT-C software for analysis of variance.Analysis of variance was made by F variance test and mean separation was performed by Duncan's Multiple Range Test (DMRT) (Gomez & Gomez, 1984).
The number of healthy fruits per plant was the lowest (15.54) in the plots treated with Boster-10 EC followed by Necstar-50 EC (19.69).However, the highest percent fruit damage (49.07) was observed in the control plots, which was significantly higher than all the insecticide-treated plots (Table 3).

Effectiveness on yield (t/ha) of brinjal:
The reduction of shoot and fruit infestation due to insecticide application ultimately improved the yield of brinjal Table 3.The results revealed that during summer the healthy fruit yield was the highest (19.94 t/ha) in Tracer-45 SC treated plots which differed significantly than all other treatments.The healthy fruit yield was the lowest in the plots treated with Boster-10 EC (7.04 t/ha) which was statistically similar to untreated control (7.27 t/ha) and Necstar-50 EC (7.58 t/ha) treated plots (Table 3).
The total fruit yield was the highest (22.82 t/ha) in Tracer-45 SC treated plots followed by Proclaim-5 SG (17.50 t/ha) and Nimbicidene 0.03 EC (16.96 t/ha), both being staistically identical.The lowest total fruit yield was recorded in plots treated with Boster-10 EC (10.30t/ha) and Necstar-50 EC (10.85 t/ha), both being statistically similar followed by control plots (14.00 t/ha) and Helicide (13.45 t/ha), (Table 3).(196.96q/ha) when five sprays of Dipel 8L(Bt) @ 0.2 percent at 10 days interval were applied and proved to be the most effective treatment.The lower effectiveness of Helicide was in accordance with the finding of the study of Ghimire et al. (2007).He recorded, higher fruit infestation both in terms of number and weight with NPV+Margosom (34.51±1.76 and 31.62±2.64%)which was (42.30 ± 4.56 and 43.57± 8.9%) with untreated control, respectively.
The results obtained in the present study suggest that the application of Tracer-45 SC performed the best in ensuring higher healthy fruit yield as well as total fruit yield of brinjal in both winter and summer seasons.Awal et al. (2014) found that Tracer-45 SC, Bactoil, Proclaim-5 SG demonstrated significantly higher mortality against 4 th instar larvae of BSFB.Jat & Preek (2001) and Misra (1993) reported that Nimbicidene was the least effective insecticide in controlling the BSFB and resulted in the lowest yield but Srinibvasan et al. (1998) reported that Nimbicidene provided higher yield (13.02 t/ha) than Endosulfan.Bactoil and Tracer-45 SC were relatively safe for natural enemies and therefore would be fit well into integrated pest management (IPM) against BSFB of brinjal crop (Awal, et al., 2015).
Therefore, it may be concluded here that the Tracer-45 SC (Spinosad) could be used in protecting the brinjal crop against BSFB and thus may ensure the highest yield per plants in both the summer and winter seasons in Bangladesh.

Table 1 . Percentage brinjal shoot borer infestation and its management with selected insecticides in two cropping seasons of the year 2009-2010
Each data represents the average of 12 observations and that of 3 replications.Data in a column followed by the same letters are not significantly different (P < 0.01, Duncan Multiple Range Test)Effectiveness on fruit infestation:The comparative effectiveness of insecticides on number of healthy, infested and total fruits per plant during summer (April to September 2009) and winter (November 2009 to May 2010) are presented in Table2 and 3.In summer, the number of healthy fruits per plant was the highest (22.38) in Tracer-45 SC treated plots followed byBactoil (17.98).The number of healthy fruits per plant was the lowest (8.58) in control which was statistically similar to Boster-10 EC (8.76) and Necstar-50 EC (8.93) followed by Helicide (13.07) and Proclaim

Table 2 . Average healthy, infested and total brinjal fruits produced in the experimental plots treated with some selected insecticides in two cropping seasons of the year 2009- 2010
Each data represents the average of 12 observations and that of 3 replications.Data in a column followed by the same letters are not significantly different (P < 0.01, Duncan Multiple Range Test)

Table 3 . Yield of brinjal fruits (healthy, infested and total) from the experimental plots treated with some selected insecticides during summer and winter, 2009-2010
Puranik et al. (2002)bir et al. (1996)r et al. (1996)evaluated several insecticides (Ralothrin 10 EC, Sunfuran 36 EC, Fenom 10 EC, Selecron 50 EC, Fastac 2 EC, Decis 2.5 EC, Arrivo 10 EC, Shobicron 4.25 EC, Cymbush 10 EC, Ripcord 10 EC, Nogos 10 EC) against BSFB over three consecutive seasons at Gazipur and Jessore district of Bangladesh and reported that none of the tested insecticides had significant effect in reducing the pest population.The less effectiveness of Nimbicidene 0.03 EC was reported byLatif (2007), which was similar to the present study.He recorded 4.31% shoot infestation in the plots treated with Nimbicidene 0.03 EC while it was 7.01% in untreated control plots.Puranik et al. (2002)reported minimum shoot (1.56%) as well as fruit (11.78%) infestation and maximum yield of marketable fruits