Papers by Prof. L. K . Hazarika
Solvent extracts of leaves of Chromolaena odorata, a widely distributed neo-tropical shrub having... more Solvent extracts of leaves of Chromolaena odorata, a widely distributed neo-tropical shrub having insecticidal properties, was tested for its safety to Trichogramma japonicum, a popular egg parasitoid of lepidopteran pests of rice, which revealed that extract toxicity could be arranged as petroleum ether < water < methanol < acetone < chloroform in terms of safety to adults causing 28.3% < 40.0% < 43.3% < 53.3% < 65.0% adult mortality at 1.0% concentration after 24 hours of treatment. Respectively, the LC 50 values of solvent extracts were 7.98%, 5.20%, 3.65%, 1.62% and 0.02%. Petroleum ether, water and methanol extracts of C. odorata at 1% concentration were ranked as harmless, however, remaining extracts were moderately harmful to the egg parasitoid even after 24 hrs of treatment.
An experiment to study the effect of temperature and diet on growth and development of the red sp... more An experiment to study the effect of temperature and diet on growth and development of the red spider mite (RSM), Oligonychus coffeae Nietner (Acarina : Tetranychidae) revealed prolongation of life cycle period up to 18.79 days at 20°C, which, however, was reduced to 8.06 days at 35°C. The longevity of adult male and female were 12.7 and 28. The red spider mite (RSM), Oligonychus coffeae Nietner (Acarina : Tetranychidae) is one of the most widespread and ancient pest of tea in northeast India having been discovered in 1868 (Harrison, 1938; Hazarika et al. 2009). It attacks the maintenance foliage and causes 17 to 43% yield loss. The larvae, nymphs and adults of RSM lacerate on cell chloroplasts of the maintenance foliage (Helle and Sabellis 1985, Walling, 2000) producing minute characteristic reddish brown marks on the upper surface of the mature leaves which turn red in severe cases. Under such situation, Rao (1974) reported up to a loss of 340 to 511 kg of made tea/ha. High temperature and dry condition are conducive for this pest. Das and Das (1967) and Haque (2007) studied the effect of temperature and relative humidity (RH) on its biology and identified 30°C as the critical temperature. They also reported that the mite did not survived beyond 35°C. However, in their natural habitat biology of mite is not only affected by abiotic challanges (temperature, RH, etc.) but also biotic factors (host plant, parasitoids, predators, etc.). In such situation interaction of temperature and host plant on the performance of the RSM is essential for developing a management strategy. Basic information in this aspect is not available. Hence, an attempt has been made to ascertain the role of temperature on development and reproductive parameters of RSM on three clones, viz TV 1 , TV 10 and TV 6 , which were identified as the susceptible, less susceptible and moderately resistant clones by Hazarika et al. (1995). Though studies on interaction between diet and temperature on tea pest are rare to find, effect of temperature and RH on the RSM (Das and Das 1967), temperature and photoperiod of Adoxophyes honmai (Nabeta et al. 2005) and evaluation of linear and non-linear developmental models on Xyleborus fornicatus (Walgama and Zalucki 2006) are common. MATERIALS AND METHOD The tea clones used for the experiments, i e TV 1 (susceptible), TV 10 (less susceptible) and TV 6 (moderately resistant) are being maintained in the Experimental Garden for Plantation Crops, Assam Agricultural University, Jorhat for last 25 years. The 4 th leaf from the top of each clones were used for all the experiments. The mites were cultured on the detached leaves in Petri-dishes of 15 cm diameter by modifying Helle and Sabellis (1985) technique (Hazarika et al. 1995). The mite infested leaves from the field were collected in a sterilized polyethene bag and brought to the Physiology Laboratory, Department of Entomology, AAU, Jorhat. These test mite stocks were cultured on detached leaves, the petioles of which were wrapped in a moist cotton plug to keep the tea
Toxicity study of Chromolaena odorata (L.) King & H. Rob. (Asteraceae) leaf powder @ 25 g/kg alon... more Toxicity study of Chromolaena odorata (L.) King & H. Rob. (Asteraceae) leaf powder @ 25 g/kg along with Beauveria bassiana (Bals.) Vuill. (Deuteromycetes) @12.5 g/kg revealed 100 and 50 adult mortality of Sitophilus oryzae (L.) (Coleoptera: Curculionidae) and Tribolium castaneum (Herbst), (Coleoptera: Tenebrionidae) at 20 days after treatment; C. odorata @100 g/ kg gave highest mortality of 29.67% in the 1st instar larvae of Corcyra cephalonica (Stainton) (Galleriidae: Lepidoptera) at 20 days after treatment. Thus C. odorata leaf powder was found to be having insecticidal and repellency properties.
The effect of nutrients (peptone, dextrose, maltose, NaCl), stickers (Tween-80 & TritonX-100) and... more The effect of nutrients (peptone, dextrose, maltose, NaCl), stickers (Tween-80 & TritonX-100) and spreaders such as oil (coconut oil, groundnut oil, mustard oil, sunflower oil), sunscreen lotion and detergents (soap, teepol) on biological parameters of Beauveria bassiana and its efficacy against larvae of Cnaphalocrocis medinalis. Three concentrations for each nutrients (0.75, 1.5 % 3.0%), stickers (0.01, 0.023 & 0.03%), oil and lotion (0.025, 0.1 & 0.5%) and detergents (0.025, 0.05 & 0.1%) were tested. The combination of all the nutrients at 0.75% concentration, Tween 80 @ 0.1% and coconut oil @ 0.5% showed the best result in respect to conidial density (177.33x10 7 conidia/ml), germination (94.9%) and mortality (90.4%) of C. medinalis. Rice is the staple diet of over half of the world's population and occupies almost one-fifth of the total world crop land under cereals. Two major factors are responsible for low yield of rice: adverse weather (floods, drought, typhoons, etc.) and pest epidemics. Out of these pest epidemics is considered as an important one. Among the major pest of rice Cnaphalocrocis medinalis Guenee has inflicted severe losses on paddy. Among all the pest management tactics, biological control by using entomopathogenic fungi, B. bassiana is the most effective. Hence, the present investigation was made to develop an alternative environment friendly pest management approach. Materials and Methods An experiment was conducted in the Department of Entomology, A.A.U., Jorhat during 2015-2016. To increase the virulancy of B. bassiana (IMI335352) the strain was initially passed through the host, Dicladispa armigera. Each cadaver was cut into many pieces and were then surface sterilized by 1% sodium hypochloride solution (NaOCl 2) for 30 sec. The sterilized pieces were then transferred to PDA medium with streptomycin sulphate and incubated at 26°C for 15 days for complete sporulation. The medium was sterilized at 15 psi for 20 min at 121 ºC in autoclave. The pure culture was prepared in PDA medium with streptomycin sulphate and incubated them at 26°C for 15 days for complete growth. Potato Dextrose Broth was utilized for mass culturing of B. bassiana (IMI335352). Carbon, nitrogen and mineral sources such as dextrose, maltose, peptone and NaCl were supplemented at a dose of 0.75, 1.5, 3.00 g / 100ml of PDB i.e. 0.75, 1.5 and 3.00% to improve the quality parameters of B. bassiana. Two stickers i.e. Tween-80 and TritonX-100 were evaluated at three concentrations viz. 0.01, 0.023 and 0.03%, respectively. Different spreaders such as oil (coconut, groundnut, mustard, sunflower oils), sunscreen lotion and detergents (soap, teepol) were
Helopeltis theivora Waterhouse (Miridae : Hemiptera) is a polyphagous insect having a characteris... more Helopeltis theivora Waterhouse (Miridae : Hemiptera) is a polyphagous insect having a characteristic diet preference, as revealed through ex situ and in situ screening of Tocklai Vegetative (TV) clones. Second instars caused the most feeding lesions (193.00 ± 8.91), but not the damage, amongst the developmental stages, and were capable of discriminating tested TV clones. Stadia of five instars were almost similar but were significantly different from adult longevity (15.58 to 18.25 days); adults exhibited not only female-biased sexual dimorphism in longevity but also of feeding potential. In situ screening resulted in identification of TV1 and TV7 as the susceptible clones, while TV6, TV12, TV14 and TV19 as resistant ones; these data were at par with that of ex situ screening in the laboratory, therefore, this method may be useful for large scale screening.
Experiments were carried out to determine the insecticidal activity of Aegle marmelos Correa agai... more Experiments were carried out to determine the insecticidal activity of Aegle marmelos Correa against Callosobruchus chinensis L. in the laboratory. Plants were extracted with petroleum ether, methanol, ethanol and water by using Soxhlet apparatus and tested against adult of C. chinensis. Plant extracts were showed insecticidal activity by affecting through mortality, oviposition deterrence and inhibition of F 1 adult emergence. Among the solvent extracts petroleum ether was found to be significantly superior over rest of the solvent extracts, registered the highest percent of mortality (82%) at 5% conc. after 96 hour of treatment followed by methanol (80%), ethanol (76%) and water extract (74%) respectively. Highest oviposition deterrence was found in petroleum ether extract (59.74%), followed by methanol (57.32%), ethanol (56.07%) and water extract (55.28%) respectively at 5% conc. after 7days of seed treatment. In terms of inhibition rate, petroleum ether extract at 5% conc. was found to be most effective (75.91%), followed by methanol (74.50%), ethanol (73.87%) and water extract (70.28%) respectively from 1 st day to 10 th days of adult emergence. The leaf extract at different doses significantly reduced oviposition and adult emergence of C. chinensis in treated green gram seeds.
Experiments were carried out to determine the insecticidal activity of Aegle marmelos Correa agai... more Experiments were carried out to determine the insecticidal activity of Aegle marmelos Correa against Callosobruchus chinensis L. in the laboratory. Plants were extracted with petroleum ether, methanol, ethanol and water by using Soxhlet apparatus and tested against adult of C. chinensis. Plant extracts were showed insecticidal activity by affecting through mortality, oviposition deterrence and inhibition of F 1 adult emergence. Among the solvent extracts petroleum ether was found to be significantly superior over rest of the solvent extracts, registered the highest percent of mortality (82%) at 5% conc. after 96 hour of treatment followed by methanol (80%), ethanol (76%) and water extract (74%) respectively. Highest oviposition deterrence was found in petroleum ether extract (59.74%), followed by methanol (57.32%), ethanol (56.07%) and water extract (55.28%) respectively at 5% conc. after 7days of seed treatment. In terms of inhibition rate, petroleum ether extract at 5% conc. was found to be most effective (75.91%), followed by methanol (74.50%), ethanol (73.87%) and water extract (70.28%) respectively from 1 st day to 10 th days of adult emergence. The leaf extract at different doses significantly reduced oviposition and adult emergence of C. chinensis in treated green gram seeds.
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Papers by Prof. L. K . Hazarika