During the past six decades chemical preparations have plays an important role and dominated in pest control. This has led to pollution of environment, danger to humans and developing resistance against toxicants of over 500 species of insects and mites (Thomas, 1999), forcing scientists to develop new kinds of insecticides. Plant products and microbials have been the subject of thorough investigation for the past few years and have emerged as an excellent alternative to synthetic insecticides for the management of insect pests. The compounds from plants having insecticidal property shows a number of useful activities like toxicity, repellence against feeding and oviposition, deterrence and insect growth regulator activity etc. (Mordue, 2004).
Cruciferae pests are one of the most limiting factors in cabbage production. The monitoring of cabbage fields at ICAR, Umiam, Meghalaya in 2010 showed high densities of large white butterfly, Pieris brassicae (L.) populations. The cabbage white butterfly, Pieris brassicae (Linnaeus) (Lepidoptera: Pieridae) is a serious pest of cabbage (Bhalla and Pawar, 1977) and the insect pest alone causes more than 40% of yield loss of vegetables annually (Ali and Rizvi, 2007). It causes extensive damage in almost all parts of India including north eastern states, during seedling, vegetative and flowering stages of cole crops (Lal and Ram, 2004; Younas et al., 2004).
Bio-insecticides are distinguished for their favorable eco-toxicological traits and low initial toxicity. The efficacy of bio-pesticides depends considerably on application timing and the aim of this investigation was to assess the bio-efficacy of eco-friendly insecticides against Pieris brassicae.
1 Materials and Methods
Field experiments were conducted during 2009-2010 in Entomology Division of ICAR Research Complex for NEH Region at Umiam, Ri-Bhoi, Meghalaya (Table 1). The cabbage variety; ‘Wonder Ball’ was transplanted on November, 2009 on the plot size of 3 x 2.5 m² and a plant to plant distance of 45 cm x 45 cm. Thirty plots having Pieris brassicae infestation were selected and five cabbages/plot were tagged. The treatments consisted of Annonin, Azadirachtin (oil base 300 ppm), Neem Seed Kernel Extract 300 ppm, Garlic Extract (1%), Karanjin, Bacillus thuringiensis (Bt), Beauveria bassiana, Spinosad 45 SC and Endosulfan 35 EC. The experiment was carried out in Randomized Block Design (RBD) and each treatment was replicated three times. The treatments were applied at the time of incidence of pests and all the treatments were sprayed with the help of a knapsack sprayer with spray volume of 1 litre/plot. Pre-treatment observations on the number of insect pests before the application of treatments was taken and post-treatment observations on the number of insect pests were recorded at 1, 3, 5, 10 and 15 days after treatment (DAT). The data pertaining to various aspects of bio-efficacy of eco-friendly insecticides against P. brassicae were statistically analyzed by using ANOVA in Randomized Block Design.
Table 1Bio-efficacy of insecticides in reducing larval population of P. brassicae during 2009-2010 at Umiam |
2 Results and Discussion
The pre-treatment count for Pieris brassicae larval population recorded one (1) day before insecticidal application varied from 29.73 to 45 larvae/plant. Treatment endosulfan recorded the lowest number of larvae (9.67 larvae/plant) with larval mortality of 67.47% one (1) day after spray followed by karanjin, spinosad and annonin which did not differs significantly from each other but these differed from all the remaining treatments.
At three (3) days after spraying, treatment endosulfan again recorded the lowest number of larvae (2.07 larvae/plant) with larval mortality of 93.03% followed by spinosad with 2.33 larvae/plant having larval mortality of 93.73%. The treatment endosulfan was at par with treatments like annonin, karanjin, spinosad which were found to differ significantly from azadirachtin 300 ppm, neem seed kernel extract 300 ppm, garlic extract (1%), Bacillus thuringiensis (Bt), Beauveria bassiana and control.
The observations after five (5) days of spray showed that all treatments differ significantly from control. The treatment endosulfan recorded the lowest number of larvae (0.53 larvae/plant) with larval mortality of 98.21% which was at par with annonin (0.67 larvae/plant), karanjin (0.87 larvae/plant) and spinosad (1.27 larvae/plant). Endosulfan was found significantly superior over Bacillus thuringiensis (28.0 larvae/plant), azadirachtin 300 ppm (30.20 larvae/plant), neem seed kernel extract 300 ppm (33.53 larvae/plant), garlic extract 1% (22.07 larvae/plant) and Beauveria bassiana (23.00 larvae/plant).
After ten (10) days of spray, endosulfan was found significantly superior over the remaining treatments with least number of larvae (0.27 larvae/plant) and larval mortality of 99.09%, followed by annonin (0.33 larvae/plant), spinosad (0.80 larvae/plant) and karanjin (2.80 larvae/plant) respectively which were at par in their effectiveness. However, endosulfan, annonin, karanjin, spinosad were found to be significantly superior over azadirachtin 300 ppm, neem seed kernel extract 300 ppm, Beauveria bassiana, Bacillus thuringiensis (Bt), garlic extract (1%) and control.
The subsequent evaluation after fifteen (15) days of spray showed that endosulfan, annonin, and spinosad were at par in their effectiveness with least number of larvae (0.40, 0.53 and 0.80 larvae/plant respectively) with larval mortality of 98.65%, 98.47% and 97.84% respectively and were found to be effective than azadirachtin 300 ppm, neem seed kernel extract 300 ppm, garlic extract (1%), karanjin, Bacillus thuringiensis (Bt), Beauveria bassiana and control which recorded 5.87 to 47.00 larvae/plant lower than the former treatments but at par in their effectiveness.
Maximum yield was obtained from endosulfan (16.2 t/ha) followed by annonin (15.00 t/ha), garlic extract 1% (14.62 t/ha), spinosad (14.60 t/ha), Bacillus thuringiensis (14.52 t/ha), neem seed kernel extract (14.50 t/ha), Beauveria bassiana (14.32 t/ha), azadirachtin (14.28 t/ha), karanjin (13.98 t/ha) and control (8.28 t/ha). Therefore, it can be concluded that the yield in the plots which have been treated with eco-friendly insecticides are higher than the control plot.
Effective control of Pieris brassicae on cabbage was also reported with extract of Azadirachta indica (Sharma and Gupta, 2009), neem extract (Przybyszewski, 1993 and Grisakova et al., 2006), neem and garlic (Khan et al., 1994), spinosad (Harris and Maclean, 1999 and Klokočar-Šmit Zlataet al., 2007), Bacillus thuringiensis (Lama, 1990; Gupta and Sood, 2003 and Prabhakar and Bishop, 2009), Beauveria bassiana (Sabbour and Sahab, 2005) and endosulfan (Ram and Pathak, 1992 and Ojha et al., 2004).
Acknowledgement:
The authors are highly grateful to Dr. S.V. Ngachan, Director, ICAR Research Complex for NE Region, Umiam, Meghalaya for providing necessary facilities for this research work.
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