Insect pest complex of linseed and management of Dasyneura lini Barnes
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Date
2017-07
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Department of Entomology, BAU, Sabour
Abstract
The investigations on insect pests of linseed and management of D. lini were conducted at Experimental Farm, Bihar Agricultural University, Sabour during Rabi season of 2016-17. A total of nine insect pests (D. lini, Thrips palmi Karny, Frankliniella schultzei (Trybom), Agrotis ipsilon Hufnage, Helicoverpa armigera Hübner, Spilosoma obliqua Walker, Monolepta signata Olovier, unidentified aphids and wire worm) and four natural enemies (Coccinella septumpunctata L., Menochilus sexmaculatus (Fabricius), Oxyopes sp. and Paederus sp. were found to be associated with linseed. The highest population of A. ipsilon (1.00 larva/m2) and thrips (26.60 nymphs & adults/plant) were observed during 52nd and 9th SMWs, respectively. However, the highest population of aphids (2.40 aphids/plant), Helicoverpa (1.00 larvae/m2), Oxyopes (1.00 spider/plant) and coccinellids (1.0 coccinellid/plant) were observed during 8th SMW. Similarly, the maximum fresh bud fly infestation (6.12%) was also recorded during the 8th SMW. Minimum temperature had positive correlation (P=0.01) with the population of A. ipsilon, H. armigera and cumulative bud fly infestation, whereas maximum temperature showed positive correlation (P=0.01) with cumulative bud fly infestation. Minimum relative humidity and population of A. ipsilon were found to be positively correlated (P=0.01), whereas maximum relative humidity had negative correlation (P=0.01) with H. armigera and cumulative bud fly infestation. Out of 101genotypes screened for resistance against the infestation of D. lini, 12 genotypes were categorized as resistant, 65 as moderately resistant, 17 as moderately susceptible, 05 as susceptible and 02 as highly susceptible. The field trial on different dates of sowing revealed that the infestation of D. lini increased and yield decreased in all five tested varieties in
progressive manner with delay in date of sowing. The lowest mean bud fly infestation (13.39%) and highest mean yield (1385.30 kg ha-1) was obtained with the crop sown on 08.11.2016, whereas the highest mean bud fly infestation (37.46%) and lowest mean yield (177.75 kg ha-1) was obtained with crop sown on 08.01.2017. The application of insecticides showed significant reduction in bud fly infestation and increased yield over untreated check. The minimum bud fly infestation (8.25%) was recorded with the application of fenvalerate 20 EC being at par with imidacloprid 17.8 SL (8.57%) followed by spinosad 45 SC (9.87%) at 15 days after second spray. Among the insecticides/bio-pesticides, the maximum infestation (16.26%) was recorded with neem leaf extract followed by fipronil 5 SC (12.31%) and dimethoate 30 EC (10.87%). The maximum incremental yield (5.21 q ha-1) was obtained with fenvalerate followed by imidacloprid (4.54 q ha-1) and spinosad (3.29 q ha-1). However, the minimum incremental yield (0.39 q ha-1) was obtained with neem leaf extract followed by fipronil (2.05 q ha-1) and dimethoate (3.06 q ha-1). The maximum benefit-cost ratio (15.12:1) was obtained with fenvalerate followed by imidacloprid (11.47:1) and dimethoate (5.92:1). However, minimum benefit-cost ratio (0.30:1) was obtained with neem leaf extract followed by fipronil (1.42:1) and spinosad (1.86:1).
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