Effect of neem seed oil on Helicoverpa armigera on pigeonpea in Nigeria

The population of Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) and its damage to pod/seed in pigeonpea was monitored upon treatment with formulated neem seed oil (F-NSO) and synthetic pyrethroid-cypermethrin. The experiment was conducted at the Postgraduate Teaching and Research Farm, Department of Crop Science and Technology, Federal University of Technology, Owerri, beginning from May 2009, repeated in May 2010 and July 2010. The experiment was laid out in 5 × 3 factorial comprising three rates of neem seed oil, 4.2 l ha−1, 8.3 l ha−1, 12.5 l ha−1 with untreated control (0l ha−1), and synthetic pyrethroid-cypermethrin 1.5 l ha−1 as check plots and three intervals of application: once a week, once in two weeks, and once in three weeks. Results revealed that application of F-NSO at highest dose of 12.5 l ha-1 and at four regime spraying intervals of once a week significantly reduced the population resulting in reduced pod and seed damage irrespective of the planting seasons. However, applying the control measure during July planting season when the population of the H. armigera was the most minimal further enhanced the performance of the early maturing pigeonpea cultivar based on the better seed quality obtained (% wholesome seeds) compared with that of May planting season.