Platygaster diplosisae and Aprostocetus proceraeare two parasitoids associated with the rice gall midge Orseolia oryzivora rice. The population of both parasitoids was monitored in three irrigated rice schemes including Banzon, Karfiguéla and Vallée du Kou, Western Burkina Faso during two consecutive wet cropping seasons 2017 and 2018 and two consecutive dry cropping seasons 2018 and 2019. The objective of this study was to investigate the ecology of the two parasitoids in the perspective of the development of a biological control strategy. In each irrigated rice scheme, four plots of 500 m² each, spread 50 m apart were randomly selected in farmers’ fields and used for the study. In each plot, a light trap was implemented along one of the diagonals of the plot. Each light trap consisted of a yellow plastic round bowl containing soapy water almost at half the bowl and a torch. The bowl had a capacity of 4.5 l, a diameter of 28 cm and a height of 10.5 cm. The torch had 3 batteries of 1.5 V each, 30 cm long and 1 cm diameter. The torches were lit every night at 6 pm and off at 6 amplots and collection was weekly. One hundredrice tillers were randomly removed along the two diagonals of each sampled plot and brought back to the laboratory. The tillers were dissected and the pre-immature populations of O. oryzivora and its associated parasitoids were recorded. Four hundred tillers were randomly removed per month from each of the alternative hosts of O.oryzivora in order to evaluate the monthly gall count, pre-imaginal populations and parasitism associated with O. oryzivora and its cousin, O. bonzii that is hosted by Paspalum scrobiculatum. The results showed that the two parasitoids associated with O. oryziovora can reduce the attacks of the midge by 42% (pupal parasitism) and 30% (larval parasitism) on cultivated rice. By providing hosts for the two parasitoids, Paspalum scrobiculatum and Oryza longistaminata ensured their survival in the absence of cultivated rice.
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