Influence of Different Planting Dates on the Occurrence of Key Pests Affecting Blackgram in the Lower Gangetic Alluvial Plain of West Bengal

Abstract

A field oriented experiment was executed over two consecutive summer months in 2019 and 2020 to study the influence of sowing dates of blackgram or urdbean (Vigna mungo L. Hepper) on the population fluctuation of its major pests viz., flower infesting thrips (Megalurothrips sp.) and spotted pod borer or legume pod borer (Maruca vitrata Fabr.). The blackgram variety PU 31 was sown on three different dates, with ten days apart specifically, on the 14th of March, 24th of March and 3rd of April each year, representing early, medium and late sown crops. The experiment recorded fewer incidences of flower thrips in late-sown crop (population of 2.56 per 10 flowers in first year and 1.22 in second year) than early crop (4.71 and 2.42 in those years, respectively), while higher incidences of pod borer was recorded in late-sown crop (larval population of 2.49 plant-1 in first year and 2.58 in second year) than early crop (0.69 and 0.42 in those years, respectively). Given that early and late-sown crops attract more thrips and pod borers, respectively, it may be recommended to sow black gram during the last week of March, especially in the lower Gangetic plains of West Bengal.