Roshmi Borah ¹, S. K. Dutta ¹

Affiliations
1 Department of Entomology, Assam Agricultural University, Jorhat 785013, Assam, IN

Abstract

Feeding potential of the aphidophagous coccinellid beetle, Coccinella transversalis F., was studied under laboratory conditions at Assam Agricultural University, Jorhat. The first instar larvae of C. transversalis were less voracious than older instars. The voracity (no. of aphids consumed/24h) of C. transversalis increased in succeeding instars. The fourth instar larva of C. transversalis consumed 65.67 apterous adults of L. erysimi in 24h and the overall consumption during the entire fourth instar was 252.90 apterous adults. The theoretical effectiveness was worked out as 107.50, which was a product of multiplication of its seasonal average numbers in the field by its average daily consumption.

Keywords

Coccinella transversalis, Feeding Potential, Lipaphis erysimi.

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Roshmi Borah ¹, S. K. Dutta ¹

Affiliations
1 Department of Entomology, Assam Agricultural University, Jorhat 785013, Assam, IN

Abstract

Predatory potential of aphidophagous syrphid fly, Episyrphus balteatus (De Geer) (Diptera:Syrphidae) against Lipaphis erysimi (Kaltenbach) was studied under laboratory conditions. The first instar larvae of E. balteatus were less voracious than older instars. The voracity (no. of aphid consumed/24 hr) of E. balteatus increased with succeeding instars. The third instar larva of E. balteatus consumed 120.2 apterous adults of L. erysimi in 24 hrs and during its entire third instar, it consumed 499.24 apterous adults. The theoretical effectiveness was worked out as 84.57, which was the product of multiplication of its seasonal average numbers in the field by its average daily consumption, which showed its potential for use as an effective biocontrol agent against mustard aphid.

Keywords

Episyrphus balteatus, Syrphidae, Feeding Potential, Lipaphis erysimi.

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Mareena Sorokhaibam ¹, S. K. Dutta ¹

Affiliations
1 Department of Entomology, College of Agriculture, Assam Agricultural University, Jorhat 785 013, Assam, IN

Abstract

Field studies were conducted to study the spatial distribution of Cheilomenes sexmaculata (Fabricius) during summer and kharif seasons, 2009 at instructional cum research farm of Assam Agricultural University, Jorhat, Assam. Various indices of dispersion were used to study the distribution pattern. In both seasons, the variance to mean ratios were found to be less than unity, dispersion parameter 'k' was less than 8 and David and Moore's indices of clumping were negative. Also, Lloyd's indices of mean crowding were less than mean and indices of patchiness were less than unity, indicating positive binomial (regular) distribution of C. sexmaculata at both larval and adult stages.

Keywords

Spatial Distribution, Green Gram, Aphis craccivora, Cheilomenes sexmaculata.

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Saurabh Sarma ¹, D. K. Saikia ¹, Badal Bhattacharyya ¹, S. K. Dutta ¹

Affiliations
1 Department of Entomology, Assam Agricultural University, Jorhat - 785013, Assam, IN

Abstract

The seasonal incidence of sugarcane woolly aphid, Ceratovacuna lanigera Zehntner (Homoptera: Aphididae), and its natural enemies was studied at Instructional-Cum-Research (ICR) Farm, Assam Agricultural University (AAU), Jorhat and at Sugarcane Research Station (SRS), Buralikson, Golaghat during 2004-05. Out of five species of natural enemies recorded at ICR Farm, AAU, Jorhat, Eupeodes confrater (Wiedemann), Chrysoperla carnea (Stephens), Coelophora biplagiata (Mulsant) and Dipha aphidivora (Meyrick) had significant positive impact on sugarcane woolly aphid population, while non-significant negative correlation of aphid population was observed with the population of Encarsia flavoscutellum Zehntner. Multiple regression analysis of different natural enemies with the population of C. lanigera showed 89.0 per cent relationship with the aphid population. At SRS, Buralikson, Golaghat, the only observed natural enemy D. aphidivora showed significant positive impact on woolly aphid population.

Keywords

Ceratovacuna lanigera, Encarsia flavoscutellum, Population Build Up, Predators, Sugarcane.

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K. K. Sarma ¹, S. K. Dutta ¹, B. K. Borah ¹

Affiliations
1 Department of Entomology, Assam Agricultural University, Jorhat 785 013, Assam, IN

Abstract

The interaction of Coccinella transversalis Fabricius and lschiodon scutellaris (Fabricius) with the aphid, Aphis craccivora Koch was studied on green gram by estimating the prey and predator populations at weekly interval. Populations of both the predators had positive correlation with the aphid, attaining population peak simultaneously with their prey. The population decline of the prey was followed by their predators.

Keywords

Aphis craccivora, Coccinella transversalis, Ischiodon scutellaris, Interaction.

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