Purpose Pesticide overuse has caused a series of negative impacts on environment and human health. The purpose of this paper is to examine the farmers’ behavior of pesticide overuse and to identify the underlying determinants, based on the survey data from Shandong Province, China. Design/methodology/approach A two-stage semiparametric approach and the binary probit model were employed in this study to analyze the marginal pesticide productivity and investigate the determinants of the pesticide overuse. Findings Results suggest that the marginal pesticide productivity is negative, indicating a serious overuse of pesticides in the surveyed area. Both market factors and government regulation have impacts on farmers’ use of pesticides. Originality/value This study estimates marginal pesticide productivity with an innovative methodology, and explores the role of market factors and government regulation in regulating farmers’ behavior of pesticide use, especially in a typical vegetable growing area and targeting a specific type of vegetable.