Lepidopteran stemborers (Chilo zacconius Bleszynski, Chilo diffusilineus de Joannis and Maliarpha separatella Ragonot) and diopsid flies (Diopsis spp.) are economically significant insect pests of rice in Burkina Faso. The objective of this study was to monitor damage trends and the pre-imaginal populations of these insects on two host plants, cultivated (Oryza sativa L.) and wild rice (Oryza longistaminata Chev and Roehr). The study was conducted over four consecutive rice crop seasons from 1999 to 2001 in three irrigated rice-growing locations in western Burkina Faso. Sampling of cultivated rice was conducted monthly in 1 m2 quadrates in 100 randomly selected farmers' fields. Data on wild rice were collected monthly from each of the three locations using 500 tillers that were plucked at random and dissected. Results showed that in the absence of a rice crop lepidopteran stemborers and diopsid flies are able to survive on O. longistaminata, which can host the pre-imaginal populations of these insects throughout the year. Damage caused on cultivated rice varied across farmers' fields, seasons and phenological stages of the plants. With 8% the highest average extent of ‘whiteheads’ was recorded during the dry season. These results are important elements in the design of a sustainable management strategy for these insect pests.