Please use this identifier to cite or link to this item: http://krishikosh.egranth.ac.in/handle/1/5810002936
Authors: Chaudhari, Vaibhav K.
Advisor: Desai, H.R.
Title: Development of economic threshold level and quantifying resistance build up in leafhopper (Amrasca biguttula biguttula Ishida) on cotton under south Gujarat condition
Publisher: AGRICULTURAL ENTOMOLOGY DEPT., N.M. COLLEGE OF AGRICULTURE, NAVSARI AGRICULTURAL UNIVERSITY, NAVSARI
Language: en
Type: Thesis
Agrotags: null
Abstract: Investigations on “Development of economic threshold level and quantifying resistance build up in leafhopper (Amrasca biguttula biguttula Ishida) on cotton under south Gujarat condition” were carried out at Main Cotton Research Station, Surat during 2013-14. The part research on development of economic threshold level (ETL) of leafhopper was carried out in split plot design with Bt hybrids (RCH 2 BG II and G. Cot. Hy. 8 BG II) as main treatments and eight sub treatments comprising of six different action thresholds, complete or calendar based sprays and untreated control. Field experiment with 16 treatment combinations was carried out during Kharif 2013-14. The part research on quantifying resistance build up in leafhopper through bioassay studies was carried out in the laboratory, Main Cotton Research Station, Navsari at an average room temperature of 27.19 ± 5.38 oC and average relative humidity of 60.63 ± 2.40 per cent during September to October 2013. Leafhopper was active from 36th meteorological standard week (MSW) (third week of August) to 49th MSW (third week of December ) and crossed recommended existing ETL of 2.0 nymphs leaf-1 for 8 times during its peak activity in untreated control irrespective of varieties. There was no spray in sub treatment of untreated control whereas in the sub treatment of complete protection average 10.0 spays were made against leafhopper populations. Effect of main and sub treatment indicated that the leafhopper densities at same action thresholds between two varieties were remained equal. Presuming difference in inherited tolerance nature of the Bt hybrids, ETL was worked out separately for both the Bt hybrids considering economic criteria. On RCH 2 BG II, action thresholds of 1.5, 2.0 and 3.0 nymphs leaf-1 were equally effective in managing leafhopper and registering equal seed cotton yield. Yield infestation relationship was found significant. Increase in seed cotton yield was more or less similar in action thresholds of 1.0, 1.5 and 2.0 nymphs leaf -1 recording 51.65, 50.02 and 49.98 per cent, respectively. These action thresholds also recorded more or less similar avoidable seed cotton yield losses (33.33 to 34.06 per cent). The maximum net realization (44245 ` ha-1) was registered in action threshold of 2.0 nymphs leaf-1 with high benefit cost ratio of 1:2.20. The marginal revenue (20867.98 ` ha-1) just exceeded management cost of 6125.27 ` ha-1 at the action threshold of 2.0 nymphs leaf-1 when compared from action thresholds from higher to lower density. The marginal rate of return was found higher (3.41) in action threshold of 2.0 nymphs leaf-1. Hence, action threshold of 2.0 nymphs leaf-1 considered as the ETL in economic term. On G. Cot. Hy. 8 BG II also, the action thresholds of 1.0, 1.5 and 2.0 nymphs leaf-1 were equally effective in managing leafhopper and registering equal seed cotton yield. Yield infestation relationship was found significant only with the action thresholds and not with the actual mean density observed. The population of leafhopper never reached the treatment of action threshold of 5.0 nymphs leaf-1 during the season. The increase in seed cotton yield was more or less similar in action thresholds of 1.0, 1.5 and 2.0 nymphs leaf-1 (55.66 to 57.49 per cent). These action thresholds recorded more or less similar avoidable yield losses (35.76 to 36.51 per cent). Maximum net realization (56122.40 ` ha-1) was received in the action threshold of 1.5 nymphs leaf-1 followed by action threshold of 2.0 nymphs leaf-1 but the benefit cost ratio was more or less equal. The marginal rate of return was found higher (5.21) in treatment of action threshold of 2.0 nymphs leaf-1 which implied that the action threshold of 2.0 nymphs leaf-1 would be the operative ETL in economic term. The LC50 estimated for insecticides showed higher values than earlier reported for the same insecticides indicated resistance built up. The resistance in the leafhopper populations against imidacloprid and thiamethoxam (78.24 to 108.68 fold) amongst neonicotinoids was found at the moderate level whereas in organophosphates, it was at low level (9.29 to 29.04 fold) in monocrotophos and acephate when compared to insecticide exposed and unexposed field populations in absence of base line data.
Subject: Agricultural Entomology
Theme: Thesis
These Type: M.Sc
Issue Date: 2014-07
Appears in Collections:Master Degree Theses

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