Management of thrips (Megalurothrips distalis Karny) on green gram (Vigna radiata L.) through dates of sowing and insecticides.
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Date
2016
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Dr. Rajendra Prasad Central Agricultural University, Pusa (Samastipur)
Abstract
In order to study the seasonal abundance and management of mungbean thrips, Megalurothrips distalis Karny through pest monitoring, manipulation in dates of sowing and relative efficacy of synthetic insecticides and plant products, a series of filed experiments were conducted during the summer season 2015-16 at the research farm, T.C.A. Dholi, Muzaffarapur, (Bihar). Results pertaining to different aspects of the present study viz; seasonal abundance, manipulation in dates of sowing and foliar spray of synthetic as well as botanical insecticides applied against thrips on mungbean crop have been abstracted below:
The activity of thrips per plant on summer mungbean commenced from 17th standard week of April, 2015 and continued to 24th standard week of June, 2015 with maximum thrips population (5.6 thrips/plant) in the 22nd standard week of June, 2015 when the corresponding maximum, minimum temperature (oC), relative humidity (%) at 07 and 14 hrs and rainfall (mm) were 40.5, 27.5, 87.7, 46.7 and nil respectively.
The activity of thrips on flower has been initially observed in 18th standard week of May, 2015 and continued to 20th standard week of May, 2015, respectively with maximum thrips population of 6.6 thrips per flower during 18th standard week of May, 2015 when corresponding maximum, minimum temperature (oC), relative humidity (%) at 07 and 14 hrs and rainfall (mm) were 34.5, 21.3, 89.5, 66.1 and nil respectively.
Among all the dates of sowing under test, 1st April proved as the most suitable date of sowing keeping in view to minimize the pest population on plant (2.4 thrips/plant) and flower (1.3 thrips/ flower), plant infestation (11.17%) and obtaining higher grain yield (14.6q/ha).
Among the synthetic insecticides and plant products under test, significantly better control of mungbean thrips was achieved imidacloprid 17.8 SL (@0.005%), when applied twice at fortnightly intervals starting from bud formation stage with thrips population of 1.4, 1.8 and 2.4 thrips per plant as against 3.6, 4.0 and 4.4 thrips per plant in untreated control after 1st and 2nd spraying respectively which was equally effective to dimethoate 30 EC thiomethoxam 25 WG, profenophos 50 EC and triazophos 35 EC, applied at their test doses respectively.
The phytotonic effect of different treatments under test, two rounds spraying of imidacloprid 17.8 SL (@ (0.005%), gave the best phytotonic effect with the maximum mean plant height (84.43 cm), number of braches per plant (9.2) and average number of pods per plant (48.2), followed by dimethoate, thiomethoxam, profenophos, triazophos, fipronil, YBSE, spinosad, neem oil respectively.
The highest grain yield of summer mungbean (14.8qa/ha) was obtained with imidacloprid but did not differ significantly from dimethoate (13.1qa/ha), thiomethoxam (13.0qa/ha), profenophos (12.3qa/ha), triazophos (11.8qa/ha), fipronil (10.5qa/ha), spinosad (9.1qa/ha), applied at their test doses as against 7.2q/ha over untreated control.
The investment of foliar application of imidacloprid, dimethoate, thiomethoxam, profenophos, triazophos, fipronil, spinosad, proved profitable in comparison to neem oil and yam bean seed extract at their test doses.
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