Augmentative Management of Chilo partellus (Swinhoe) by Cotesia flavipes Cameron in Maize crop.
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Date
2015
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Rajendra Agricultural University, Pusa (Samastipur)
Abstract
In order to study the augmentative management of Chilo partellus (Swinhoe) by Cotesia flavipes Cameron in maize crop, the experiments were conducted in the laboratory as well as field during Kharif 2014. The biology of Chilo partellus was studied during its mass production, on natural host (maize) and on semi-synthetic diet under laboratory condition. On natural host, incubation period varied from 3 - 6 (4.66 ± 1.52) days. The total larval period varied from 18 - 30 days (23.66 ± 6.02) in which the first, second, third, fourth and fifth instars lasted for 3 to 5 days (4.33 ± 1.16), 3 to 5 days (3.66 ± 1.15), 4 to 6 days (4.66 ± 1.16), 4 to 7 days (5.33 ± 1.52) and 4 to 7 days (5.66 ± 1.53) respectively. The pupal period lasted for 6 to 9 days (7.66 ± 1.52). The longevity of male and female moths reared in laboratory ranged from 2 to 4 days (2.66 ± 1.15) and 3 to 5 days (3.66 ± 1.61) respectively. The total life cycle of Chilo partellus varied from 30.0 to 50.0 days (41.66 ± 6.72). On semi-synthetic diet, however, incubation period varied from 3-4 days (3.33 ± 0.57). The total larval period varied from 13 to 24 days (18.66 ± 5.59). The pupal period lasted for 5 to 8 days (6.66 ± 1.52). The longevity of male and female moths ranged from 3 to 6 days (4.66 ± 1.53) and 4 to 6 days (5.33 ± 1.16) respectively. The total duration of life cycle of Chilo partellus varied from 25 to 42 days (34.33 ± 6.12). The biology of Cotesia flavipes was also studied on Chilo partellus during its mass production. The egg-larval period on an average lasted for 8 to 12 days (10.2 ± 1.48). The pupal period was 3 to 5 days (3.8 ± 0.83) with adult longevity 2-3 days (2.33 ± 1.01). The total life cycle of Cotesia flavipes on Chilo partellus lasted for 13 to 20 days (16.8 ± 3.76). The maximum parasitization by Cotesia flavipes on Chilo partellus occurred during August recording 40 per cent and minimum during September recording 25 per cent. The infestation of Chilo partellus on maize was observed from 37th standard week (12.5 per cent) which increased till 42nd standard week (41.21 per cent) and then gradually decreased till 50th standard week (19.86 per cent). All the weather parameters like temperature, relative humidity and rainfall was found negative and insignificant. The coefficient of determination was only 13 per cent indicating a very low contribution of weather factors during the period under observation. The parasitization of Cotesia flavipes on Chilo partellus under natural condition was observed from 37th standard week (8.50 per cent) which increased till 47th standard week (42.3 per cent) thereafter, gradually decreased till 50th standard week (14.6 per cent). The relative humidity was found negative and significant whereas temperature and rainfall was found negative and insignificant. The coefficient of determination was 65 per cent indicating high contribution of weather factors. The parasitization of Cotesia flavipes on Chilo partellus under augmentation condition was observed from 37th standard week (18.50 per cent) which increased till 47th standard week (51.00 per cent) thereafter, gradually decreased till 50th standard week (18.0 per cent). The relative humidity was found negative and significant whereas temperature and rainfall was found negative and insignificant. The coefficient of determination was 56 per cent indicating high contribution of weather factors.
Impact of recovery of Cotesia flavipes parasitization on Chilo partellus in maize crop revealed the superiority of the augmented plot value (O) to the expected value (E) recorded in the natural infestation plot which was significant at 5 per cent level tested through Chi-square (). The maximum parasitization observed under (E) was 42.3 per cent while the same observed under (O) was 51.0 per cent. Hence, the net gain of augmentation was only 8.7 per cent, which was significant at 5%. The high level of parasitization of Chilo partellus by Cotesia flavipes under natural condition (42.3 per cent) virtually masked the impact of augmentation. Biological control is a very slow and self perpetuating process. The presence of native Cotesia flavipes in the agro-ecosystem and the ease in handling this tool for augmentative use is an encouraging indication for its possible further exploitation in the management of lepidopteran borers in other graminacious crops.
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