ESTIMATION OF RICE YIELD LOSSES DUE TO THE AFRICAN RICE GALL MIDGE, ORSEOLIA-ORYZIVORA HARRIS AND GAGNE

The African rice gall midge, Orseolia oryzivora Harris and Gagne (Dipt era: Cecidomyiidae), is an important pest of rice, Oryza sativa, in Bu rkina Faso as well as other countries in West and East Africa. In spit e of its importance, little is known regarding the relationship betwee n gall midge populations and grain yield losses. To determine yield lo sses the gall midge was reared in cages and adult midges were placed o n caged plants of the rice variety ITA 123 at different population lev els. The seven treatments consisted of different numbers of insects in fested on the plants; 0 insect pairs (noninfested check), and 1, 5, 10 , 15, 20 or 25 midge pairs/cage. The loss in yield in relation to the non-infested control was highly positively correlated (R(2) = 0.81) wi th the percentage of gall midge damaged tillers. The infestation by th e insect on the plants resulted in the compensatory production of till ers which developed in response to the gall midge damage but the compe nsation was not sufficient to make up for the loss of yield due to the damaged tillers. Yield loss ranged from 0% in the control to 65.3% in the treatment with 25 pairs of adults. One per cent of tillers damage d resulted in 2% grain yield loss.