Pest status of the rice stem-borers, Diopsis longicornis and D. apicalis was not well known in the Republic of Guinee. / In the present study, adult and immature populations of both species were monitored under various local cultural practices, i.e., planting methods (direct and transplanted), different planting dates and seasons (wet and dry). As previously observed in other West African countries, D. apicalis did occasional damage to rice in Guinee. However, contrary to findings elsewhere, D. longicornis was not an important pest of Guinean rice, infesting 4% of stems over the five seasons studied. / Regulators affecting population size and behaviour of D. longicornis were determined, focusing on factors controlling the fly's quiescent period in aggregation sites during the dry season, and the insect's movement to and from these refugia. Availability of cultivated and wild rice was found to interrupt or prevent quiescence of D. longicornis. Abiotic factors, (relative humidity, rainfall and photoperiod) influenced time of dispersal of D. longicornis.

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