Ecology of the African Rice Gall Midge, <i>Orseolia oryzivora</i> (Diptera: Cecidomyiidae) in Western Burkina Faso, West Africa

Abstract

The African rice midge, Orseolia oryzivora H. & G., is an important insect pest in Burkina Faso. Our study was conducted from 2017 to 2019 in three irrigated rice schemes including Banzon, Karfiguéla and Vallée du Kou in Western Burkina Faso. The objective of this study was to investigate the ecology of the insect pest. In each rice scheme, four plots of 500 m 2 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 am. Four hundred tillers were collected per month from the cultivated rice and from each of the alternative hosts of the rice midge 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 number of O. oryzivora's adults caught in the light traps was higher during the wet season than the dry season. The level of larval parasitism ranged from 6.16% (Banzon) to 14.29% (Vallée du Kou). The highest level of pupal parasitism (13.73%) was recorded in Vallée du Kou. The damage of O. oryzivora was observed on the wild rice species, O. longistaminata in all three sites. The highest levels of parasitism associated with O. bonzii were recorded in Karfiguéla (20.08% and 25.21% for larval parasitism and pupal parasitism, respectively