Effect of Irrigation, Date of Sowing and Nitrogen on the Incidence of Mustard Aphid, Lipaphis erysimi Kalt.

Abstract

Investigations were carried out on the effect of irrigation, date of sowing and nitrogen on population of mustard aphid during Rabi 1995-96 and 1996-97 at College Farm, Gujarat Agricultural University, Junagadh. Pooled results revealed that frequent irrigation (15 days interval) increased the incidence (24 aphids/10 cm tender shoot during 13th WAS) of mustard aphid. The early sown crop (up to 15 October) escaped from infestation of aphid, but infestation was highest from pod formation stage to harvest (15.80 to 102.73 aphids/10 cm tender shoot) in crop sown on 15th November. In case of fertilizer, the crop receiving heavy dose of nitrogen (75 kg/ha) suffered more, as 26.12 aphids/10 cm tender shoot were recorded during 13th WAS. Interaction effects indicated that the crop escaped from the incidence of aphid in early sown crop (up to 15th October) when irrigated at an interval of 20 days (4 irrigations). Similar interaction effect was recorded in early sown crop fertilized with 25 kg N/ha.