Management of major insect pests in soybean
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Date
2015
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MPUAT, Udaipur
Abstract
The present investigations on “Management of major insect pests in soybean” was conducted at Agricultural Research Station-Borwat Farm, Banswara, Maharana Pratap University of Agriculture and Technology, Udaipur during kharif-2012 and 2013, with the objectives of studying their seasonal incidence, species diversity, estimation of losses, effect of sowing dates and varieties and evaluation of different insecticide spray schedules.
The major insect pests were recorded on soybean, included white fly, Bemisia tabaci (Genn.), semilooper, Chrysodeixis acuta (Wlk.), girdle beetle, Obereopsis brevis (Gahan), gram pod borer, Helicoverpa armigera (Hubn.) and tobacco caterpillar, Spodoptera litura (F.).
During both the crop seasons kharif-2012 and 2013, the peak population of whitefly was observed in the last week of August (35th SMW) and 2nd week of September (37th SMW), respectively. The population of whitefly had a significant positive correlation with the maximum temperature and sunshine hours while, significant negative correlation with rain fall and morning and evening relative humidity only during kharif-2013. The maximum population of semilooper was recorded in the 2nd week of September (36th SMW) and last week of September (39th SMW), respectively. The semilooper exhibited a significant and positive correlation with minimum temperature, morning evening humidity and rain fall during both the years. The highest girdle beetle damage was recorded in the last week of August (35th SMW) and 2nd week of September (37th SMW), respectively; whereas, the maximum incidence of gram pod borer was recorded in the 2nd week of September (36th SMW) and last week of September (39th SMW), respectively. The larval population of gram pod borer exhibited a significant negative correlation with sunshine and minimum temperature during experimental period; whereas, it exhibited a significant positive correlation with rainfall and relative humidity during both the years. The maximum incidence of tobacco caterpillar in soybean crop was recorded during 2nd week of October (41st SMW) and 3rd week of October (42nd SMW), respectively. The maximum temperature and sunshine hours showed a significant positive correlation with the larval population of tobacco caterpillar, while; significant negative correlation with rainfall during both the years.
Twenty two insect pests were recorded on soybean during the experimental period. During the year 2012, the mean density (%) value was the maximum 79.26 per cent for white fly; whereas, during the year 2013, the mean density (%) value was the maximum 73.33 per cent for semilooper. During kharif-2012, the whitefly was relatively more 35.87 per cent while, during kharif-2013, maximum 28.87 per cent relative density (%) was recorded for semilooper. The Shannon Diversity Index was 1.45 and 1.55 during the year 2012 and 2013, respectively.
During kharif -2012 and 2013 the reduction in plant height and numbers of pods per plant was 8.58 and 11.68 per cent and 12.23 and 24.31 per cent, respectively. Likewise, the loss in mean number of seeds per pod and weight of 100 seeds was 11.06 and 14.86 per cent and 7.28 and 8.00 per cent, respectively. The loss in mean yield was 23.79 and 37.16 per cent; during 2012 and 2013, respectively. During the year 2012 and 2013 the crop sown during 1st week of July had significantly higher incidence of whiteflies and girdle beetle as compare to crop sown in the 3rd week of July; whereas, the incidence of semilooper, gram pod borer and tobacco caterpillar was significantly lower in the crop sown in the 1st week of July as compare to crop sown in the 3rd week of July. During the kharif- 2012 and 2013 significant lowest incidence of whitefly and tobacco caterpillar was recorded in the soybean variety of RKS-24 while, the significant lowest incidence of semilooper, gram pod borer and girdle beetle was observed in the JS-95-60 variety of soybean. The significantly highest yield with mean of 1564 and 1650 kg ha-1 was recorded in case of soybean crop sown during the first week of July in the year 2012 and 2013, respectively. Among the varieties, the highest seed yield of 1840 kg ha-1 and 1812 kg ha-1 was recorded in RKS-24 during the year 2012 and 2013, respectively; which was significantly gave higher yield than other varieties except, JS-335.
Two sprays were given in soybean crop from different insecticidal spray schedules, of which first spray was given against whiteflies, semilooper and girdle beetle at 35 days after germination (DAG) and second spray was given at 55 DAG against gram pod borer and tobacco caterpillar. During both the years in first spray, the significant maximum per cent reduction in white fly population was recorded in case of thiamethoxam 25 WG at 3, 5 and 7 days after spray. While, significant highest per cent reduction in the larval population of semilooper and girdle beetle was recorded in case of profenophos 50 EC at 3, 5 and 7 days after spray. In the second spray, indoxacarb 14.5 EC @ 345 ml ha-1 caused significantly maximum reduction of gram pod borer and tobacco caterpillar larvae at 3, 5 and 7 days after spray.
The highest seed yield, net profit and C : B ratio were obtained in case of spray schedule comprising first spray of triazophos 40 EC @1.25 lit ha-1 at 35 DAG followed by second spray of flubendiamide 480 SC @ 100 g ha-1 at 55 DAG with the corresponding respective values 1925 kg ha-1, Rs. 15,008 ha-1 and 1:8.52.
Description
Studies on management of major insect pests in soybean
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Citation
Kalyan and Ameta 2015