Bioecology and Management of Sorghum Mite, Oligonychus indicus Hirst (Acarina: Tetranychidae) on Sorghum
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Date
2006
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MPUAT, Udaipur
Abstract
The present investigation entitled, “Bioecology and management of sorghum mite, Oligonychus indicus Hirst. (Acarina: Tetranychidae) on sorghum” was carried out in the Department of Agricultural Zoology and Entomology, Rajasthan College of Agriculture, MPUAT, Udaipur (Raj.) during kharif 2003 and 2004 with a view to know the host range, comparative biology, population dynamics of O. indicus, to screening few germplasm and evaluation of the bioefficacy of acaricides against O. indicus.
The study on survey shows that five cultivated plants viz., sorghum [Sorghum bicolor (L.) Moench.], maize (Zea mays L.), sawan (Echinochloa frumentacea L.) bajra (Pennisetum typhoides L.) and sugarcane (Saccharum officinarum L.) and two weeds, bandrabandri (Setaria glauca L.) and Jhonson grass (Sorghum helpanse L.) were infested by O. indicus. The average life span of Oligonychus indicus Hirst. was longest (16.01 to 16.61, 29.03 to 30.76 and 36.16 days for the male, mated and unmated females respectively) on sugarcane while, it was shortest on bajra (10.38 to 11.58, 17.53 to 17.94 and 20.10 to 20.63 for the male, mated and unmated females, respectively). The atmospheric temperature and humidity ranged from 24.12 to 24.20 0C and 60.42 to 61.75%, respectively). The female to male ratio was recorded to be maximum (84:16) on bajra, while minimum (64:36) on sugarcane. The total number of eggs laid per female varied from 42.25 to 48.56 and 32.62 to 35.61 for the mated and unmated females, respectively. Eggs which measured 0.120 to 0.121 mm in diameter. The biometrical data for two years showed that larva was 0.140 mm in length and 0.145 to 0.147 mm in width for the male while it was 0.148 to 0.149 mm in length and 0.145 to 0.147 mm in width for the female. The protonymph measured 0.221 to 0.223 and 0.242 to 0.244 mm in length and 0.145 to 0.146 and 0.180 mm in width for the male and female, respectively. The deutonymph measured 0.256 to 0.257 and 0.282 to 0.283 mm in length and 0.191 to 0.192 and 0.23 to 0.277 mm in width for male and female, respectively. Adults of the mite measured 0.317 to 0.319 and 0.402 to 0.404 mm in length and 0.225 to 0.226 and 0.276 to 0.277 mm in width for the adult male and female, respectively.
The incidence of the mite started from 37th SMW and reached its peak during 44th SMW (2.26 and 2.25 mites per leaf bit during 2003 and 2004 respectively) while abundance of eggs reached its peak in the 44th SMW (2.53 and 2.29 eggs per leaf bit during 2003 and 2004, respectively). The mite preferred bottom canopy for feeding as well egg laying. Significant negative correlation was found for the mite and eggs with temperature and relative humidity.
The abundance of the predatory mite, Amblyseius sp. started from 37th SMW (during 2003) and 36th SMW (during 2004), reaching the peak during 45th SMW (0.64 and 0.47 predatory mite/leaf bit for 2003 and 2004, respectively). The correlation coefficient, between the predatory mite with temperature and relative humidity were significantly negative. Abundance of the predatory beetle, Stethorus pauperculus Weise stared from 39th SMW and reached its maximum at 44th SMW (0.33 and 0.25 beetle/leaf during 2003 and 2004, respectively). Significant positive correlation existed between the predators and prey mite, while it was significantly negative for temperature and relative humidity.
Of the different sorghum germplasm screened, the mite population the maximum on variety SU 658 (0.56 and 0.73 mite per leaf bit during 2003 and 2004, respectively), while, it was minimum on SPV 14730, SPV 1472 and CSV 17 (0.02 mobile stages per leaf bit during 2003 and 2004). The mite population and abundance of eggs were higher on germplasm having yellow–green leaf colour vis-a- vis leaf width was less than 6 cm (CSV I0, SU 1, SPV 15 and SU 658), while it was less on germplasm which had tan pigmentation vis-a-vis leaf width more than 6 cm (SPV 1430, SPV 1472 and CSV 15 ).
Among the acaricides evaluated, Dicofol (0.04 %) was most effective in reducing the mite population (74.70 to 76.27 %) followed by endosulfan (0.075%) which gave 66.76 to 72.84 per cent reduction in the mite population while Ethion (0.10 %) was most economic on the basis of C: B ratio (1:2.38 to 1:2.50 during 2003 and 2004, respectively).
Description
Bioecology and Management of Sorghum Mite, Oligonychus indicus Hirst (Acarina: Tetranychidae) on Sorghum
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Citation
Chundawat and Sharma, 2006