An improved integrated pest management model under 2-control parameters (sterile male and pesticide) S. Bhattacharyya * ,1 , D.K. Bhattacharya Department of Pure Mathematics, University of Calcutta, 35, B.C. Road, Calcutta 700 019, India Received 25 January 2006; received in revised form 19 June 2006; accepted 7 August 2006 Available online 17 August 2006 Abstract The object of the present paper is to study an integrated pest management (IPM) problem in an agro- ecosystem (paddy–fish culture) through mathematical modeling and analysis, where release of sterile males and spraying of pesticide have been used as control measures for pest population. Using optimal analysis of the model, we have shown that restricted and proper use of control measures might enhance the crop pro- duction of the system in an economically viable way. The paper also considers the vulnerability of the underlined ecosystem due to the effect of temperature on the pest growth. Using Liapunov-like function, we have found out a suitable range of temperature, where this IPM strategy remains effective. Some impor- tant remarks have finally been made on the basis of numerical simulation. Ó 2006 Elsevier Inc. All rights reserved. Keywords: Integrated pest management; Sterile males; Vulnerability of the system; Singular control; Pontryagin’s maximum principle 1. Introduction Sterile insect technique (SIT) is one of the most effective biological control for pests in the paddy– fish culture system (integrated production system). Some deep water paddy varieties are being 0025-5564/$ - see front matter Ó 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.mbs.2006.08.003 * Corresponding author. Tel.: +91 033 2632 2407. E-mail address: samit_math@rediffmail.com (S. Bhattacharyya). 1 Research supported by National Board for Higher Mathematics (NBHM), DAE, India. www.elsevier.com/locate/mbs Mathematical Biosciences 209 (2007) 256–281