BIODIVERSITY AND ECOLOGY OF BLISTER BEETLES IN CROP ECOSYSTEMS
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Date
2014
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MPUAT, Udaipur
Abstract
Investigations on “Biodiversity and ecology of blister beetles in crop ecosystems” were carried out in the Department of Entomology, Rajasthan College of Agriculture, MPUAT, Udaipur, during the kharif seasons from 2012 to 2013 with a view to record the species diversity in the agro-climatic Zone IV (a) of Rajasthan; the bio-ecology and morphometrics of the dominant species; develop a diagnostic tool for the species; and evaluate the ant-feedant activity of some botanicals against them. The conducted surveys over the two year period resulted in the collection and identification of 6 genera and 10 species of blister beetles: Mylabris pustulata Thunberg, Mylabris phalerata (Pallas), Mylabris sp., Lydomorphus (Cylindrothorax) ornata (Cast), Lydomorphus (Cylindrothorax) rouxi (Cast), Lydomorphus (Cylindrothorax) ruficollis (Fabricius), Decapotoma rouxi (Lap.); and Denierella sp., Epicauta sp. and Hycleus sp.; of which two species of the genus Mylabris (M. phalerata and M. pustulata) were dominant.
The initial infestation of blister beetles was in the 33rd SMW on greengram and in the 36th SMW on pigeonpea. The maximum population of the beetles was recorded on blackgram, greengram in the 37th SMW, on cowpea in the 38th SMW and on pigeonpea in the 41st SMW. Wind velocity and sunshine had a more pronounced effect on the blister beetle population on all the pulses observed during the two kharif seasons, having a significant and positive association. Based on the relative density (%) of blister beetles on different pulse crops, year-wise, the blister beetles (Mylabris spp.) frequently foraged during 33 to 35 SMW on greengram (32.84 to 40.54 in 2012 & 10.32 to 48.39 in 2013), blackgram (28.69 to 30.68 in 2012 & 13.99 to 48.41 in 2013) and cowpea (30.75 to 36.49 in 2012 & 17.24 to 69.93 in 2013), while during 36 to 44 SMW on pigeonpea (35.58 to 38.80 in 2012 & 35.84 to 37.71 in 2013).
The numerical abundance of blister beetles on a per plant basis was relatively more on greengram, blackgram and cowpea in the presence of pigeonpea. The blister beetles exhibited a special preference for pigeonpea as the relative plant effect (RPE) values were negative (ranging from – 0.30 to – 0.61 in 2012 and from – 0.79 to – 0.95 in 2013) on the different pulse crops observed. It was concluded from the food preference studies that female blister beetles preferred to feed on China rose (207.00 to 209.50 mg/day); while the males preferred the mixed food comprising flowers of all 6 plants (96.50 to 99.75 mg/day). Blackgram was least preferred (27.75 to 29.75 mg/day) both by males and females.
Study on the biology evinced that the females laid eggs during the second week of September, 2012. The mean incubation period was 39.0 days. The mean duration of the first larval stage (triungulin) was 15.0 days and the duration of remaining immature stages lasted for 269.0 days and adults emerged after 323.0 days. The adult longevity was 51 days.
The morphometric data as linear measurements of the length and width of body, elytra; length of antenna; width of labrum, mandible and labium for the males and females of the 10 blister beetle species collected during the investigation have been given. The females and males of Mylabris phalerata Pallas were the largest among the blister beetles collected. On the basis of body length, in a decreasing order, the species were Mylabris phalerata > M. pustulata > Epicauta sp. > Cylindrothorax rouxi > Denierella sp. > Mylabris sp. > C. ornata > C. ruficollis > Hycleus sp. > Decapotoma rouxi.
The aqueous leaf extracts (10%) of A. indica (neem) and E. hirta (dudhi), seed kernel extract (5%) of A. indica and seed oils (1%) of A. indica, P. pinnata (karanj) and Eucalyptus sp. (safeda) were evaluated for anti-feeding activity against the blister beetle M. pustulata. On the basis of area (cm2) and quantum (%) of okra flowers consumed in 24 hours, neem seed kernel extract (NSKE 5%) had the maximum anti-feeding activity with significantly minimum area and quantum of okra flowers consumed at different days after the treatments {(1-DAT: 4.0cm2, 13.33%), (3-DAT: 8.45cm2, 28.17%) and (5-DAT: 13.00cm2, 43.33%)} in 2012; likewise, {(1-DAT: 4.08cm2, 13.58%), (3-DAT: 7.80cm2, 26.00%) and (5-DAT: 13.03cm2, 43.42%)} in 2013. In the untreated control, the area consumed ranged from 23.27 to 23.43 sq. cm.; and the quantum consumed ranged from 77.56 to 78.03 per cent during 2012; likewise, the area consumed ranged from 22.38 to 23.83 sq. cm.; and the quantum consumed ranged from 74.58 to 79.42 per cent during 2013. The anti-feeding action of NSKE (5%) resulted in reduction in the area and quantum of the untreated flower consumed 5-DAT, which was almost half the area and quantum consumed in comparison to that consumed in the untreated control.
Description
BIODIVERSITY AND ECOLOGY OF BLISTER BEETLES IN CROP ECOSYSTEMS
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Citation
Jat and Ameta, 2015