Studies aimed at setting up a system of rational control of pests were carried out at the Vallée du Kou rice irrigation scheme near Bobo-Dioulasso in 1986. The first part of the study focuses on the phytosanitary survey of the above mentioned rice irrigation scheme of 1043 ha through a network of observation sites. This part has given prominence to the fact that the development and importance of the pest infestation were affected by the spacing out of the rice planting and has also allowed us to locate the critical periods of the infestations and their economic incidence. These pests consist mainly of lepidopterous stem borers: Chilo sp., Sesamia sp., and Maliarpha separatella.

The second part of the study focused on phytosanitary experiments. Using Decis (Deltamethrin) at 12.5 g a.i. per ha at the intervention thresholds of 5% dead heart and 1% whitehead, has proved to be the most interesting formula as it combines efficiency and profitability.

The system of rational control that has been set up based on phytosanitary survey and insecticide application at threshold levels, presents a double advantage, it reduces the number and cost of interventions, and limits the anarchical use of pesticides, hence their harmful effect on the environment. Such experience in insect pest management will be extended to other rice growing areas throughout the country.