C. T. Williams, M. N. Uiwungwu, B. N. Singh, O. Okhidievbie, J. Nnabo. 1999. Farmer-managed trials in south-east Nigeria to evaluate the rice variety Cisadane and estimate yield losses caused by African rice gall midge, Orseolia oryzivora. International Journal of Pest Management 45 (2): 117-124.

Keywords: paired comparisons of Cisadane with farmers’ control varieties, relationships between infestation level and yield, farmers’ evaluations of Cisadane, the performance and evaluation of Cisadane, effects of gall midge infestation on yield.

Abstract: Farmer-managed trials of the rice variety Cisadane were undertaken at 47 rainfed lowland sites around Abakaliki, south-east Nigeria, a major outbreak area of the African rice gall midge (ARGM). At each site a plot of Cisadane was grown alongside a control plot of the participating farmer's usual variety. On average the Cisadane yielded 26% higher than the controls but ARGM infestation levels on it were only slightly lower, suggesting that had greater tolerance to the pest but little anti-xenotic or antibiotic resistance. For all of 14 evaluation criteria, most participating farmers rated Cisadane as better than their control varieties. It appears to be a useful component for an ARGM management strategy. Regression analyses of yield on alternative variables for ARGM infestation derived from data recorded at 3, 7 or 11 w.a.t. (weeks after transplanting) showed that the log-transformed percent tiller infestation at 7 w.a.t. was

the best predictor of yield. Variables for site topography, water level, fertilizer use in the nursery, and plant spacing also had significant partial regression coefficients. Excluding plots with tiller infestation levels above 30%, the relationship between yield and infestation was approximately linear and suggested a yield loss of 2.9% per 1% increase in infestation.