Insect incidence and damage on pearl millet (Pennisetum glaucum) under various nitrogen regimes in Alabama

Abstract

Although pearl millet [Pennisetum glaucum (L.) R. Br.; Poales: Poaceae] is grown extensively on 5 continents and is attacked by various insects at all stages of growth and development, little is specifically known of how yields of this important crop are affected by insect herbivory. This study was conducted in north central Alabama to determine insect occurrence on pearl millet and to determine the levels of damage caused by insects feeding on pearl millet genotypes at different nitrogen rates. The field experiment was laid out following a randomized complete block design with 4 replications in which 4 genotypes and 4 fertilizer levels were arranged in factorial combinations. The pearl millet genotypes consisted of 2 open pollinated lines, '2304' and 'LHBO8', and 2 hybrids, '606A1∗2304' and '707A1∗4280' and fertilization rates used were 0, 40, 80 and 120 kg ha-1 N. Insect samplings were carried out weekly from 61 to 109 days after planting (DAP). Insects in 6 orders and 11 families were found on pearl millet genotypes. Eastern leaf-footed stinkbug (Leptoglossus phyllopus (L.); Hemiptera: Coreidae) was the most prevalent and dominant insect species found followed by the American bird grasshopper (Schistocerca americana Drury; Orthoptera: Acrididae) and the differential grasshopper (Melanoplus differentialis (Thomas: Orthoptera: Acrididae). Population of L. phyllopus was at its peak during the latter part of the growing season from 81 to 109 DAP. Populations of S. americana and M. differentialis declined as crop matured (61 DAP > 66 DAP >75 DAP). Results also showed that leaf and head damage did not differ among genotypes and nitrogen rates tested.