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D. N. Yadav ¹, M. M. Sarin ², S. Krishnaswami ²

Affiliations
1 Bhabha Atomic Research Centre, Trombay, Mumbai - 400085, IN
2 Physical Research Laboratory, Earth Science Division, Ahmedabad - 380 009, IN

Abstract

Geochemical analysis of groundwater samples and brines from the Sambhar Salt lake shows a predominance of NaCl with respect to total salt content (TDS), which varies from 0.5 to -400 g/L. All brine (lake + shallow subsurface) samples indicate a Na-Cl type alkaline solutions with pH varying from 8.5 to 10. All this suggests a general provenance for halite or dissolution of desiccated salt minerals in the catchment and drainage areas of the lake. Adjacent groundwaters are mostly neutral Na-Cl type with TDS ranging from 0.5 to 13 g/L. In contrast to groundwaters, the river waters from Roopangarh and Mendha reflect that out of the TDS, the major ions constitute Na, Alk and Cl with an average equivalent Na/Cl ratio of 2.7, indicating dissolution of Na from silicate weathering of rocks. However, the lake water composition overwhelms the river water upon mixing during the recharge period. A complete annual wetting and drying cycles of evolution of lake brine shows generation of Na-Cl type of brine with steady increase in major ions except Ca and Mg ions which decrease in successive stages of evaporation. Relative change in Na and Cl ions is also observed during the late stage of evaporation at or beyond halite saturation stage. Observation of such chemical change in brine composition is in line with the identification of salt minerals in lake sediments and salt encrustation by XRD technique.

In present-day hydrologic set-up, the estimated salt inventory in lake is _10⁶ tons as compared to riverine input of 6x10⁴ tons and an upper limit of aeolian input of about 5xl0⁴ tons. Such an estimate indicates that majority of salt is derived from the recycling and re-solution of salt encrustation from the lake bed during recharge period.

Keywords

Hydrogeochemistry, TDS, Nacl, Brines, Annual Wetting and Drying Cycles, Evaporation, Brine Evolution, Salt Encrustation, Aeolian Salt Input, Recharge Period, Sambhar Salt Lake, Rajasthan.

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D. N. Yadav ¹, M. S. Chauhan ², M. M. Sarin ³

Affiliations
1 Bhabha Atomic Research Centre, Trombay, Mumbai - 400 085, IN
2 Birbal Sahni Institute of Palaeobotany, 53 University Road, Lucknow - 226 007, IN
3 Earth Science Division, Physical Research Laboratory, Ahemdabad - 380 009, IN

Abstract

A 15 m deep sedimentary core from Jagmotha swamp in northeastern Madhya Pradesh has been analyzed for reconstruction of Late-Quaternary vegetation and climate change based on distribution of major/Trace elements, organic carbon, nitrogen and pollen grains contained in the sediments. The combined geochemical and palynological results indicate a cool and dry climate between 6000 to 5000 yrs BP representing a tree savannah type vegetation followed by warm and moist climate between 5000 to 3000 yrs BP. Such a drastic change in climate promoted tropical mixed deciduous forests in the region. Subsequently, between 3000 to 1200 yrs BP, the climatic condition got further improved with enhanced precipitation in the region marked by the advent of sal tree in the forest floristics. Since then, the climate has been inferred conducive for development of modern sal forests in the region.

Keywords

Palaeoclimate, Palaeovegetation, Late-Quaternary Period, Major/Trace Element Geochemistry, Organic Carbon and Nitrogen, C/N Ratio, Pollen Frequency.

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S. K. Pathak ¹, D. N. Yadav ²

Affiliations
1 Tea Research Association. 15 Cooch Behar Road. Darjeeling 734101, West Bengal, IN
2 Department of Entomology, B.A. College of Agriculture Gujarat Agricultural University Anand Campus, Anand 388110, Gujarat, IN

Abstract

Three different methods were tried to find out suitable laboratory technique for mass rearing of Eublemma scitula Ramb. (Lepidoptera: Noctuidae) an important predator of brown scale insect Saissetia coffeae Walker (Homoptera: Coccidae) a serious pest of pointed gourd, Trichosanthes dioica Roxb in and around Anand, Gujarat. Out of these rearing methods, namely, a) on pointed gourd leaves, b) on green potato sprouts and c) on pumpkin fruits, the method c), which involved either releasing E. scitula eggs (c 1) or larvae (c 2) on pumpkin fruit with growing scale population was observed to be the best for mass rearing of the predator with seed to yield ratio of 1: 0.63 and 1: 0.73 in c 1 and c 2, respectively. On an average, 69.4 and 73 pupae could be produced in methods c 1 and c 2, respectively. from a single pumpkin in a single generation of the scale, within two months (October to November). The technique was found to be suitable for mass rearing of E. scitula to augment the predator during June July for suppression of the host S. coffeae at its initial stage of infestation. Limitations observed in other methods of rearing were described.

Keywords

Biocontrol, Eublemma scitula, Saissetia Coffeae, Trichosanthes dioica.

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F. K. Dhulia ¹, D. N. Yadav ¹

Affiliations
1 AICRP on Biological Control of Crop Pests and Weeds, Gujarat Agricultural University, Anand - 388 110, IN

Abstract

Studies on the biology of Oxyopes ratnae Tikadar showed that the spider laid on an average 2.8 egg masses during the life span. The average incubation period was 10.1 ± 0.74 days and number of spiderlings emerging per egg mass varied from 30-42, with an average of 35.6 ± 3.82. Males and females passed through 10 and 11 instars, respectively to reach maturity. Male and female spiderlings took an average of 187.20 ± 4.87 and 259.50 ± 4.18 days, respectively to complete the development from egg to adult. The total average life span of adult in case of male and female was 305.8 and 358.80 days, respectively. The males and females mated readily under laboratory conditions, the mating lasted for a few seconds. Mortality during different instars varied from 4.00 to 70.64 %. The females spun silken cocoons before laying eggs and covered them with silken threads. It was also found to take care of the eggs by sitting over them.

Keywords

Oxyopes ratnae, Biology, Cotton.

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B. C. Joshi ¹, D. N. Yadav ¹

Affiliations
1 All India Coordinated Research Project on Biological Control of crop pests and weeds, Gujarat Agricultural University, Anand-388 110, IN

Abstract

Biology and feeding potential of a chrysopid, Mallada boninensis Okamoto, recorded by us for the first time from Gujarat, were studied under laboratory conditions. The predator laid stalked eggs in groups usually of 11 to 20. The larvae with the habit of carrying trash on its back passed through three Instnrs, the durations of which were 4.11, 4.11 and 4.63 days at a constant temperature of 25.26 ± 2.2 °C and 59.90% RH. The short prepupal and pupal periods averaged 5 to 7 and 13.79 days respectively. The female was slightly bigger than male. The sex ratio of male:female was 1:1.5 with 81.40 per cent emergence of adults. Pre oviposition, oviposition and post-oviposition periods averaged 9.90 ± 1.60, 36.90 ± 4.41 and 18.00 ± 12.24 days respectively. The total number of eggs laid by the female averaged 431 ± 38.62 eggs. The average longevity of females and males were 64.8 ± 15.97 and 27.36 ± 8.03 days respectively. The larva consumed on an average 628.75 eggs of Corcyra cephalonica Stainton and 453 nymphs of white flies.

Keywords

Mallada boninensis, Bemisia tabaci, Corcyra cephalonica, Development, Biology, Feeding Potential.

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B. M. Parasharya ¹, J. F. Dodia ¹, D. N. Yadav ¹, R. C. Patel ¹

Affiliations
1 Dept. of Entomology, Gujarat Agricultural University, Anand 388 110, IN

Abstract

The castor semilooper, Achaea janata Linn. appeared in epidemic form during September-October, 1985. A total of eighteen species of birds were recorded feeding on the A. janata larvae. About 300 Rosy Pastors, Sturnus roseus fed on A. janata for 8 days. Due to the heavy bird predation on large size larvae, pupal count was reduced. Egg parasitism by Trichogramma chilonis Ishii and Telenomous sp. progressively increased from 50.0 to 92.2 per cent. Despite heavy egg parasitism, larval density reached as high as 8.91 per plant. Heavy predation by birds and higber egg parasitism had failed to control the population of A. janata in epidemic situation.

Keywords

Achaea janata, Trichogramma chilonis, Egg Parasitism, Sturnus roseus, Bird Predation.

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